A system for hot digestion reduction coupled with liquid chromatography and atomic fluorescence

Abstract

The utility model provides a heat digestion reduction system for liquid chromatography and atomic fluorescence is used together, including heat digestion device, cooling device, sucking pump, gas -liquid separator, digestion agent container and reducing agent container. Heat digestion device includes digestion pipeline and heating device, and heating device is used for heating digestion pipeline. Cooling device includes heat dissipation board and cooling pipeline, and heat dissipation board installs on cooling pipeline and is used for heat dissipation to cooling pipeline. The utility model discloses compared with prior art in ultraviolet lamp digestion, and the higher stability of digestion efficiency is not needed to consider the risk of ultraviolet lamp breakage, and heating temperature will also reduce the memory effect in pipeline, improve hydride generation efficiency. Through setting up cooling device to the mixed liquid of measuring in pipeline after completing heating digestion is cooled, make the aerosol that generates because of heating digestion quick liquefaction, effectively reduce the system pressure in pipeline, avoid the risk of pipeline burst.

Description

Technical Field

[0001] This utility model relates to the field of analytical testing technology, and in particular to a thermal digestion and reduction system for combined liquid chromatography and atomic fluorescence spectrometry. Background Technology

[0002] Differences in the form of elements determine their physicochemical properties and biological activities, leading to differences in their behavior in the environment and life processes. For example, inorganic selenium is extremely toxic; milligram-level selenate can be fatal to humans and animals, while organic selenium can be safely consumed and absorbed by the human body. Therefore, the toxicity and harm of an element depend not only on its total content but also on its form of occurrence.

[0003] Currently, high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) is widely used for speciation analysis of elements such as arsenic, selenium, mercury, and antimony in food safety, environmental monitoring, and biological samples. However, due to the limitations of the HG-AFS testing principle, all analytes must be converted to a suitable valence state before entering the AFS detector so that they can react with sodium borohydride / potassium borohydride to produce their hydrides. Therefore, a digestion-reduction system must be provided at the instrument interface. The purpose is to convert large organic molecules or high-valence elements that cannot produce hydrides into valence states capable of hydride generation through digestion and reduction. These hydrides then enter a gas-liquid separator for reaction, and the resulting target hydride is then introduced into the AFS for detection. For example, tetravalent selenium has a 100% efficiency in producing hydrides, while organic selenium such as selenomethionine and hexavalent selenium have very low efficiency in producing hydrides, or even do not react at all. However, after digestion and reduction treatment, small molecule organic selenium and tetravalent selenium can react with sodium (potassium) borohydride to produce hydrogen selenide gas, thereby improving monitoring efficiency.

[0004] Existing liquid chromatography-hydride generation-atomic fluorescence spectrometers typically utilize a UV lamp digestion-reduction system to digest and reduce the sample from the liquid chromatograph, and then introduce the separated gas into the atomic fluorescence spectrometer for detection. However, existing UV lamp digestion-reduction systems suffer from low digestion efficiency, unstable luminescence, and fragile UV lamps. Utility Model Content

[0005] This invention provides a thermal digestion and reduction system for combined liquid chromatography and atomic fluorescence, which solves the problems of low digestion efficiency, unstable luminescence, and fragile ultraviolet lamp in the prior art.

[0006] This invention provides a thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry (LC-AFS), comprising a thermal digestion device, a cooling device, a suction pump, a gas-liquid separator, a digesting agent container, and a reducing agent container. The thermal digestion device includes a digestion pipeline and a heating device, which is installed on the digestion pipeline for heating it. The inlet end of the digestion pipeline is connected to a sample flow path and a digesting agent flow path, respectively. The end of the digesting agent flow path furthest from the thermal digestion device is connected to the digesting agent container. The cooling device includes a heat sink and cooling pipes. The heat sink is installed on the cooling pipe for heat dissipation. The inlet end of the cooling pipe is connected to the outlet end of the digestion pipeline. The outlet end of the cooling pipe is connected to a reducing agent flow path and a reducing output pipeline. The end of the reducing agent flow path away from the cooling device is connected to the reducing agent container. The suction pump is installed on the digestion agent flow path and the reducing agent flow path. The gas-liquid separator is provided with a gas-liquid inlet and a gas outlet. The end of the reducing output pipeline away from the cooling device is connected to the gas-liquid inlet.

[0007] Furthermore, it also includes a waste liquid tank, and the gas-liquid separator is provided with a waste liquid outlet, which is connected to the waste liquid tank through a pipeline.

[0008] Furthermore, two suction pumps are provided, which are respectively installed in the digester flow path and the reducing agent flow path.

[0009] Furthermore, the suction pump is configured as a peristaltic pump, and the digester flow path and the reducing agent flow path respectively pass through the peristaltic pump.

[0010] Furthermore, the cooling pipe is arranged in a curved shape within the heat dissipation plate, and the heat dissipation plate is provided with a positioning groove for the cooling pipe to be embedded.

[0011] Furthermore, the diameter of the digestion pipeline is less than 2mm and the length is less than 20m, and the diameter of the cooling pipeline is less than 2mm and the length is less than 5m.

[0012] Furthermore, the diameter of the digestion pipeline is 0.5-2mm and the length is 0.5-10m, and the diameter of the cooling pipeline is 0.5-2mm and the length is 0.5-3m.

[0013] Furthermore, the heating device is configured as an electric heating rod, and the digestion pipeline is wound around the electric heating rod.

[0014] Furthermore, it also includes a thermoelectric cooler, the cooling end of which is connected to the heat sink.

[0015] Furthermore, it also includes a controller, and temperature sensors are respectively installed on the digestion pipeline and the cooling pipeline. The temperature sensors, the heating device and the semiconductor refrigeration chip are respectively connected to the controller.

[0016] Furthermore, it also includes a preheating plate and a preheating tube connected to the inlet of the digestion pipeline. The inlet of the digestion pipeline is connected to the sample flow path and the digesting agent flow path through the preheating tube. The preheating tube passes through the preheating plate, and the preheating plate is connected to the hot end of the semiconductor cooling chip.

[0017] The advantages of this utility model providing a thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry (LC-AFS) are as follows: The digestion pipeline is heated by a heating device, thereby heating the sample mixture flowing through the digestion pipeline to achieve thermal digestion. A controller is used to precisely regulate the heating temperature, adapting to the different digestion temperature requirements of various elemental analyses. Compared to existing UV lamp digestion technologies, this method offers higher digestion efficiency and stability, and eliminates the risk of UV lamp breakage. Furthermore, the heating process reduces the memory effect in the pipeline, increasing hydride formation efficiency. A cooling device is installed to cool the sample mixture after thermal digestion within the pipeline, causing rapid liquefaction of the aerosols generated during thermal digestion, effectively reducing system pressure and avoiding the risk of pipeline rupture. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the connection relationship of this utility model.

[0019] Figure 2 This is a schematic diagram of the connection relationship when the electric heating rod of this utility model is used as a heating device.

[0020] Figure 3 This is a structural diagram of the electric heating furnace of this utility model when it is used as a heating device.

[0021] Figure 4 This is a schematic diagram showing the connection relationship when the present invention uses two reducing agent containers.

[0022] Figure 5 This is a schematic diagram showing the connection relationship between the preheating pipe and the preheating plate of this utility model.

[0023] Figure 6 This is a schematic diagram of the structure of the cooling device and the semiconductor refrigeration chip of this utility model.

[0024] Figure 7 This is a schematic diagram of the internal structure of the preheating plate of this utility model.

[0025] Figure 8 This is a schematic diagram of the internal structure of the heat exchange cavity of this utility model.

[0026] Figure 9 This is a chromatogram of the five selenium forms of this utility model.

[0027] Figure 10 This is a schematic diagram of the connection relationship of the controller of this utility model.

[0028] Figure label:

[0029] 1. Thermal digestion apparatus; 11. Digestion piping; 12. Heating device; 121. Electric heating rod; 122. Electric heating furnace; 123. Resistance heating wire; 124. Heating chamber; 2. Cooling device; 21. Heat sink; 211. Positioning groove; 212. Heat exchange chamber; 213. Coolant; 22. Cooling piping; 23. Reducing agent flow path; 24. Reduction output piping; 25. Second three-way valve; 3. Suction pump; 31. Sample flow path; 32. Digestant flow path; 33, First three-way valve; 34, Four-way valve; 35, Two-way valve; 4, Gas-liquid separator; 41, Waste liquid tank; 42, Liquid chromatograph; 43, Atomic fluorescence spectrometer; 5, Digestant container; 6, Reducing agent container; 61, High-pressure gas cylinder; 62, Third three-way valve; 7, Semiconductor cooling chip; 71, Cold end; 72, Hot end; 8, Controller; 81, Temperature sensor; 9, Preheating pipe; 91, Preheating plate; 92, Connecting groove. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0031] The terms "first" and "second" in the specification and claims of this utility model may explicitly or implicitly include one or more of those features. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates an "or" relationship between the preceding and following objects as part of a thermal digestion-reduction system used in coupled liquid chromatography and atomic fluorescence spectrometry.

[0032] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0033] The following is combined with Figures 1-10 The present invention describes a thermal digestion and reduction system for coupled liquid chromatography and atomic fluorescence spectrometry, such as... Figure 1 As shown, the device includes a thermal digestion apparatus 1, a cooling apparatus 2, a suction pump 3, a gas-liquid separator 4, a digesting agent container 5, and a reducing agent container 6. The thermal digestion apparatus 1 includes a digestion pipeline 11 and a heating apparatus 12. The heating apparatus 12 is installed on the digestion pipeline 11 to heat it. The inlet end of the digestion pipeline 11 is connected to a sample flow path 31 and a digesting agent flow path 32. The end of the digesting agent flow path 32 away from the thermal digestion apparatus 1 is connected to the digesting agent container 5. The cooling apparatus 2 includes a heat dissipation plate 21 and a cooling pipe 22. The heat dissipation plate 21 is installed on the cooling pipe 22 to dissipate heat from it. The inlet end of the cooling pipe 22 is connected to the outlet end of the digestion pipeline 11. The outlet end of the cooling pipe 22 is connected to a reducing agent flow path 23 and a reducing output pipeline 24. The end of the reducing agent flow path 23 away from the cooling apparatus 2 is connected to the reducing agent container 6. The suction pump 3 is installed on both the digesting agent flow path 32 and the reducing agent flow path 23. The gas-liquid separator 4 is provided with a gas-liquid inlet and a gas outlet, and the end of the reduction output pipeline 24 away from the cooling device 2 is connected to the gas-liquid inlet.

[0034] Specifically, such as Figure 1As shown, sample flow path 31 and digester flow path 32 are connected to the inlet of digestion line 11 via a first three-way valve 33. Sample flow path 31 is used to connect to liquid chromatograph 42 and deliver the sample solution separated by liquid chromatograph 42. Digester flow path 32 is connected to digester container 5 and used to deliver digester. Reducing agent flow path 23 and reduction output line 24 are connected to the outlet of cooling line 22 via a second three-way valve 25. Reducing agent flow path 23 is used to deliver reducing agent, and suction pump 3 provides power for the flow of digester and reducing agent. The inlet of cooling line 22 is connected to the outlet of digestion line 11 via a two-way valve 35, and heat sink 21 is used to cool the digested test solution. The cooled test solution and reducing agent are mixed in reduction output line 24, which is connected to gas-liquid inlet and gas outlet for connection to atomic fluorescence spectrometer 43.

[0035] When using the thermal digestion-reduction system, the digesting agent is injected into the digesting agent container 5, and the reducing agent is injected into the reducing agent container 6. The sample flow path 31 is connected to the liquid chromatograph 42, and the gas outlet is connected to the atomic fluorescence spectrometer 43 via a detection line. The suction pump 3 drives the digestion solution to flow from the digesting agent container 5 to the digestion line 11 within the digesting agent flow path 32. The sample to be tested from the liquid chromatograph 42 enters the digestion line 11 from the sample flow path 31. The digesting agent and the sample to be tested from the liquid chromatograph 42 are automatically mixed at the inlet of the digestion line 11 through the first three-way valve 33 and flow into the digestion line 11. The liquid chromatograph 42 is used to separate different elemental forms in the sample. The heating device 12 heats and digests the mixed sample solution through the heating digestion line 11, thereby achieving automatic mixing and heating, saving experimental time. The suction pump 3 drives the reducing agent to flow from the reducing agent container 6 to the reduction output line 24 within the reducing agent flow path 23. The digested test solution enters the cooling pipe 22, where it is cooled by a heat sink 21. The solution is then mixed with a reducing agent at the second three-way valve 25. The mixed test solution then enters the gas-liquid separator 4. The gas-liquid separator 4 provides a reaction site for the test solution and achieves gas-liquid separation. The separated target gas enters the atomic fluorescence spectrometer 43 for target element detection. When the gas pressure is insufficient, such as... Figure 1 As shown, a high-pressure gas cylinder 61 and a third three-way valve 62 are set up. The third three-way valve 62 is installed on the detection pipeline. The outlet of the high-pressure gas cylinder 61 is connected to the detection pipeline through the third three-way valve 62. The target gas generated in the gas-liquid separator 4 is sent from the detection pipeline to the atomic fluorescence spectrometer 43 for detection under the push of the carrier gas in the high-pressure gas cylinder 61.

[0036] Heating device 12 heats the digestion pipeline 11, thereby heating the test mixture flowing through it and achieving thermal digestion. Compared to existing UV lamp digestion, this method offers higher digestion efficiency and stability, and eliminates the risk of UV lamp breakage. Furthermore, the increased temperature reduces the memory effect in the pipeline, improving hydride formation efficiency. Cooling device 2 cools the digested test mixture within the pipeline, rapidly liquefying the aerosols generated during digestion, effectively reducing system pressure and mitigating the risk of pipeline rupture.

[0037] In an alternative embodiment, the digestion line 11, the cooling line 22, and other connecting lines are all made of polytetrafluoroethylene.

[0038] Furthermore, such as Figure 1 As shown, it also includes a waste liquid tank 41, and the waste liquid outlet is connected to the waste liquid tank 41 through a pipeline. The target gas separated by the gas-liquid separator 4 enters the atomic fluorescence spectrometer 43 for the detection of the target element, and the unreacted solution flows into the waste liquid tank 41 for collection through a pipeline.

[0039] In an optional embodiment, two suction pumps 3 are provided, which are respectively installed in the digester flow path 32 and the reducing agent flow path 23. The two suction pumps 3 drive the flow of the digester and the reducing agent respectively.

[0040] In another alternative embodiment, the suction pump 3 is configured as a peristaltic pump, through which the digester flow path 32 and the reducing agent flow path 23 respectively pass. The peristaltic pump drives the flow of the digester and the reducing agent.

[0041] In an alternative embodiment, such as Figure 6 As shown, the cooling pipe 22 is curved and arranged within the heat sink 21, which has a positioning groove 211 for embedding the cooling pipe 22. The curved, zigzag shape of the cooling pipe 22 within the positioning groove 211 increases the contact area between the cooling pipe 22 and the heat sink 21, thereby improving the heat exchange effect. The heat sink 21 can be made of heat-dissipating aluminum. In actual use, cooling pipes 22 of different lengths can be selected according to cooling requirements.

[0042] In another alternative embodiment, such as Figure 8 As shown, the cooling pipe 22 is arranged in a curved shape inside the heat dissipation plate 21. The heat dissipation plate 21 has a heat exchange chamber 212 through which the cooling pipe 22 passes, and the heat exchange chamber 212 is filled with coolant 213. The coolant 213 contacts the cooling pipe 22 for heat exchange, thereby achieving cooling and temperature reduction of the cooling pipe 22.

[0043] Furthermore, the diameter of the digestion pipe 11 is less than 2 mm and the length is less than 20 m. The diameter of the cooling pipe 22 is less than 2 mm and the length is less than 5 m. Specifically, the diameter of the digestion pipe 11 is 0.5-2 mm and the length is 0.5-10 m, and the diameter of the cooling pipe 22 is 0.5-2 mm and the length is 0.5-3 m.

[0044] In an optional embodiment, the heating device 12 is configured as an electric heating rod 121, and the digestion pipe 11 is wound around the electric heating rod 121.

[0045] Specifically, such as Figure 2 As shown, the digestion tubing 11 is heated by an electric heating rod 121. Different lengths of digestion tubing 11 can be wound around the heating rod as needed.

[0046] In another alternative embodiment, such as Figure 3 As shown, the heating device 12 is configured as an electric heating furnace 122. The electric heating furnace 122 is provided with a heating resistance wire 123 and a heating chamber 124 through which the digestion pipeline 11 passes. The digestion pipeline 11 is spirally arranged in the heating chamber 124.

[0047] Furthermore, it also includes a thermoelectric cooler 7, the cooling end 71 of which is connected to the heat sink 21. For example... Figure 1 As shown, the cold end 71 of the semiconductor is in contact with the end face of the heat sink 21, and the heat sink 21 is cooled by the semiconductor cooling chip 7, further improving the cooling effect. At the same time, it will cause the high-temperature aerosol in the cooling pipe 22 to liquefy quickly, effectively reducing the system pressure in the pipe and avoiding the risk of pipe rupture.

[0048] In an optional embodiment, a controller 8 is also included. Temperature sensors 81 are respectively installed on the digestion pipeline 11 and the cooling pipeline 22. The temperature sensors 81, the heating device 12 and the thermoelectric cooler 7 are respectively connected to the controller 8.

[0049] Specifically, the temperature sensor 81 can be installed inside the digestion pipe 11 and at the outlet of the cooling pipe 22, such as... Figure 10 As shown, temperature sensor 81 senses the actual thermal digestion temperature of the digestion tube and the actual cooling temperature of the sample in the cooling pipe 22. Temperature sensor 81 is electrically connected to the controller and transmits the sensed temperature signal to the controller 8. The controller 8 controls the power of the heating device 12 and the thermoelectric cooler 7 to adjust the heating and cooling temperatures online, thereby ensuring that the heating and cooling temperatures reach and stabilize at the set target values, resulting in more stable digestion efficiency. In an optional embodiment, a peristaltic pump is connected to the controller 8, and the controller 8 adjusts the pump speed of the peristaltic pump to control the flow rate of the digesting agent and reducing agent.

[0050] In an alternative embodiment, such as Figure 5 As shown, it also includes a preheating plate 91 and a preheating tube 9 connected to the inlet of the digestion pipeline 11. The inlet of the digestion pipeline 11 is connected to the sample flow path 31 and the digesting agent flow path 32 through the preheating tube 9. The preheating tube 9 passes through the preheating plate 91, and the preheating plate 91 is connected to the hot end 72 of the semiconductor cooling chip 7.

[0051] Specifically, such as Figure 6 , Figure 7 As shown, the preheating plate 91 is attached to the hot end 72 of the semiconductor cooling chip 7. Before entering the digester flow path 32, the test liquid flows through the preheating pipe 9. The preheating plate 91 is provided with a connecting groove 92 for embedding the preheating pipe 9. The test liquid passes through the preheating plate 91 through the preheating pipe 9 and exchanges heat with the preheating plate 91. At the same time, it cools the hot end 72 of the semiconductor cooling chip 7 and preheats the test liquid entering the digester flow path 32, thereby improving the energy utilization efficiency.

[0052] In practical use of the thermal digestion and reduction system of this invention for liquid chromatography and atomic fluorescence spectrometry, the corresponding number of reducing agent containers 6 and digestion agent containers 5 can be selected according to the actual types of reducing agent and digestion agent. When only one digestion agent and one reducing agent are needed, such as in the detection of selenium speciation, ... Figure 1 As shown, a reducing agent container 6 and a digesting agent container 5 are used. When one digesting agent and two reducing agents are required, such as when simultaneously detecting the elemental speciation of arsenic and mercury, etc. Figure 4 As shown, two reducing agent containers 6 and one digesting agent container 5 are used. The reducing agent flows through two reducing agent flow paths 23, which pass through the peristaltic valve and are connected to one reducing agent container 6 respectively. The outlet end of the cooling pipe 22, the two reducing agent flow paths 23 and the reducing output pipe 24 are connected through the four-way valve 34.

[0053] Specifically, when using the thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry of this invention to detect selenium speciation, sample solutions of five selenium speciations—selenomethionine, selenocysteine, methylselenocysteine, selenate, and selenite—are selected for detection. The liquid chromatograph (HPLC) uses a Hamilton PRP-X100 anion exchange column (CVP 42), and the mobile phase is a buffer solution of 40 mM diammonium hydrogen phosphate and 1 mM citric acid (pH=6.0) at a flow rate of 1.0 ml / min. The peristaltic pump operates at 60 RPM. The digestion tubing (11) has a diameter of 0.8 mm, a length of 8 m, and a temperature control of 180 °C. The digesting agent is a mixture of 5% potassium bromide (w / v) and 50% hydrochloric acid (v / v). The cooling tubing has a diameter of 0.8 mm, a length of 2 m, and a cooling temperature control of 20 °C. The reducing agent is 1.5% sodium borohydride (containing 0.35% sodium hydroxide). The laser source of the atomic fluorescence spectrometer 43 is a selenium hollow cathode lamp, and the target detection gas is hydrogen selenide.

[0054] The peristaltic pump is started, and the electric heating rod 121 and the semiconductor refrigeration chip 7 are turned on. A sample solution containing five selenium forms is injected into the liquid chromatograph 42 using a syringe. The sample flowing out of the liquid chromatograph 42 is mixed online with the digesting agent and digested in the digestion tubing 11. The digested sample is cooled to 20°C in the cooling pipe 22. After cooling, the sample is mixed online with the reducing agent and injected into the gas-liquid separator 4. The reaction produces the target hydride gas, which is introduced into the atomic fluorescence spectrometer 43 under the propulsion of the carrier gas in the high-pressure gas cylinder 61, yielding the analytical chromatogram. Simultaneously, the waste liquid is discharged through the waste discharge pipe. The chromatograms of the five selenium forms are shown below. Figure 9 As shown, based on the retention time, the selenium forms corresponding to the left side are, in order, selenocysteine ​​(SeCys2), methylselenocysteine ​​(MeSeCys), selenite (SeIV), selenomethionine (SeMet), and selenate (SeVI). Throughout the detection process, the sample is transported from the liquid chromatograph 42 to the atomic fluorescence spectrometer 43 via a pipeline. During transport, heating digestion, reduction, and gas-liquid separation are automatically completed, enabling online detection of the sample.

[0055] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0056] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A thermal digestion and reduction system for coupled liquid chromatography and atomic fluorescence spectrometry, characterized in that: The device includes a thermal digestion apparatus, a cooling apparatus, a suction pump, a gas-liquid separator, a digesting agent container, and a reducing agent container. The thermal digestion apparatus includes a digestion pipeline and a heating device. The heating device is installed on the digestion pipeline for heating the digestion pipeline. The inlet end of the digestion pipeline is connected to a sample flow path and a digesting agent flow path, respectively. The end of the digesting agent flow path away from the thermal digestion apparatus is connected to the digesting agent container. The cooling device includes a heat dissipation plate and a cooling pipe. The heat dissipation plate is installed on the cooling pipe to dissipate heat from the cooling pipe. The inlet end of the cooling pipe is connected to the outlet end of the digestion pipeline. The outlet end of the cooling pipe is connected to a reducing agent flow path and a reduction output pipeline, respectively. The end of the reducing agent flow path away from the cooling device is connected to the reducing agent container. The suction pump is installed in the digestion agent flow path and the reducing agent flow path. The gas-liquid separator is provided with a gas-liquid inlet and a gas outlet. The end of the reduction output pipeline away from the cooling device is connected to the gas-liquid inlet.

2. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 1, characterized in that: It also includes a waste liquid tank, and the gas-liquid separator is provided with a waste liquid outlet, which is connected to the waste liquid tank through a pipeline.

3. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 1, characterized in that: Two suction pumps are provided, and the two suction pumps are respectively installed in the digester flow path and the reducing agent flow path.

4. The thermal digestion and reduction system for coupled liquid chromatography and atomic fluorescence according to claim 1, characterized in that: The suction pump is configured as a peristaltic pump, and the digester flow path and the reducing agent flow path respectively pass through the peristaltic pump.

5. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 1, characterized in that: The cooling pipe is curved and installed inside the heat sink, and the heat sink has a positioning groove for the cooling pipe to be embedded.

6. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 1, characterized in that: The digestion pipeline has a diameter of less than 2mm and a length of less than 20m, and the cooling pipeline has a diameter of less than 2mm and a length of less than 5m.

7. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 1, characterized in that: The heating device is configured as an electric heating rod, and the digestion pipeline is wound around the electric heating rod.

8. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to any one of claims 1-7, characterized in that: It also includes a thermoelectric cooler, the cooling end of which is connected to the heat sink.

9. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 8, characterized in that: It also includes a controller, and temperature sensors are installed on the digestion pipeline and the cooling pipeline respectively. The temperature sensors, the heating device and the semiconductor refrigeration chip are respectively connected to the controller.

10. The thermal digestion and reduction system for liquid chromatography and atomic fluorescence spectrometry according to claim 8, characterized in that: It also includes a preheating plate and a preheating tube connected to the inlet of the digestion pipeline. The inlet of the digestion pipeline is connected to the sample flow path and the digester flow path through the preheating tube. The preheating tube passes through the preheating plate, and the preheating plate is connected to the hot end of the semiconductor cooling chip.

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