Online water removal device for membrane sampling underwater gas chromatograph

Abstract

According to the on-line water removal device for the membrane sampling underwater gas chromatograph provided by the invention, water in sampling gas is exchanged into dry environment gas in an instrument cabin by using the sleeve containing the water exchange membrane as a tube core, so that the relative humidity of the sampling gas is reduced to be less than 5%; comprising a sleeve, a flow limiter, an air pump, a stop valve, a dryer and a connecting pipeline. The technical scheme of the invention can effectively prevent the high-humidity sample gas from damaging the enrichment filler, the chromatographic stationary phase and the like in the instrument, and prolong the service life of the instrument. Meanwhile, the problems of retention time offset, separation degree reduction and target component covering by a water peak caused by a large amount of water entering a chromatographic column can be solved, and the qualitative and quantitative accuracy is improved. Meanwhile, the device has no sample introduction discrimination for conventional analysis components, has great drying capacity, does not need additional drying gas, can be directly mounted in an underwater gas chromatograph, and is suitable for underwater in-situ analysis instruments for other membrane sample introduction.

Description

Technical Field

[0001] The present invention relates to the technical field of gas chromatography analysis. In particular, it relates to an on-line water removal device for a membrane injection underwater gas chromatograph. Background Art

[0002] Dissolved gases and volatile organic compounds naturally exist in the water environment. For example, a large amount of carbon dioxide, methane, and sulfur-containing compounds will be ejected during submarine hydrothermal activities. A large amount of volatile organic compounds will be generated by submarine oil spills. The metabolism of microorganisms will produce long-chain hydrocarbons. Human activities also have a significant impact on water bodies such as rivers and lakes. Water pollution caused by wastewater discharge, the large reproduction of organisms in eutrophic water bodies, etc. will significantly change the trace components in the water. Detecting these dissolved gases and volatile organic compounds in water can provide a scientific basis for aspects such as energy exploration, environmental protection, disaster warning, research on aquatic biological communities, and the geochemical cycle.

[0003] Currently, the detection methods for dissolved gases and volatile organic compounds in water mostly use on-board analysis or laboratory analysis after sampling. This method has obvious lag. The delay between sampling and analysis will damage the integrity of the sample, and it is impossible to continuously analyze the spatio-temporal status of the substance distribution, resulting in very low detection efficiency. In-situ analysis can improve the analysis accuracy, eliminate the errors generated during sample processing, transportation, storage, etc., achieve long-term real-time observation, and reduce the consumption of human and material resources. In-situ analysis is especially suitable for the open sea, ocean, and deep sea. For these areas, the cost of bringing water samples back to the laboratory for analysis is too high, and long-term observation is even more unrealistic.

[0004] Currently, the mainstream sampling technology of in-situ analysis instruments is in-situ sampling using a water-gas separation membrane. After extracting the substances dissolved in water into the gas chamber by a membrane injection device, the gas samples in the gas chamber are analyzed by different instruments, such as underwater sensors, underwater mass spectrometers, underwater gas chromatographs, underwater spectrometers, etc. Underwater in-situ gas chromatography detection injects the gas in the gas chamber of the membrane injection device into the gas chromatograph for in-situ analysis. This method has high sensitivity and good stability, and can accurately qualitatively and quantitatively analyze complex components.

[0005] However, in the membrane injection method, the relative humidity of the sample gas phase is extremely high (∼100%). A large amount of water entering the chromatograph can cause damage to the enrichment packing and chromatographic stationary phase. At the same time, problems such as retention time shift, decreased resolution, and the water peak masking the chromatographic peaks of target components will occur, affecting the accuracy of qualitative and quantitative analysis. In laboratory gas chromatography analysis of high-humidity sample gases, there are mainly two solutions: direct adsorption by desiccants and drying with Nafion tubes. If desiccants such as molecular sieves, color-changing silica gel, and anhydrous calcium chloride are directly used to adsorb the sample gas, an injection discrimination effect will occur. In addition, limited by the dead volume problem of injection, only a small amount of desiccant (∼g) can be filled when directly using desiccants for adsorption. Therefore, the drying capacity is low and the service life is short. After multiple uses, the desiccant may become saturated and ineffective or even caked. These disadvantages make it unsuitable for the underwater gas chromatograph for long-term deployment analysis. Nafion tube drying uses a proton exchange membrane to exchange water molecules in the sample gas into the dry gas. The drying depth depends on the humidity of the dry gas. In actual use, a large flow of dry gas is required for purging, which makes the Nafion tube drying method unable to be directly used in the underwater gas chromatograph. Summary of the Invention

[0006] According to the above-mentioned technical problems, an on-line water removal device for a membrane injection underwater gas chromatograph is provided. The present invention uses a sleeve containing a water exchange membrane as the tube core to exchange the moisture in the injected gas into the dry environmental gas in the instrument cabin, so that the relative humidity of the injected gas is reduced to less than 5%.

[0007] The technical means adopted by the present invention are as follows:

[0008] An on-line water removal device for a membrane injection underwater gas chromatograph is arranged inside the instrument cabin of the underwater gas chromatograph and includes: a sleeve, a flow restrictor, a gas pump, a stop valve, a dryer, and a connecting pipeline, wherein:

[0009] The sleeve contains a water exchange membrane tube core and is a double-layer sleeve, including an inner tube and an outer tube, wherein: the two end faces of the outer tube are closed tube walls, and openings are respectively provided on the side tube walls of the outer tube near the two end faces; one end of the inner tube is connected to the air chamber of the membrane injection device of the underwater gas chromatograph through a connecting pipeline and a stop valve. The side opening of the outer tube near this end is connected to the gas pump through a connecting pipeline. The other end of the inner tube is connected to the injection pipeline of the underwater gas chromatograph through a connecting pipeline and a stop valve. The side opening of the outer tube near this end is connected to the gas in the instrument cabin inside the underwater gas chromatograph through a flow restrictor;

[0010] The gas pump and the stop valve are respectively connected to the electronic control module of the underwater gas chromatograph, and the electronic control module of the underwater gas chromatograph controls the opening and closing of the gas pump and the stop valve;

[0011] The dryer is used to maintain the humidity of the gas in the instrument cabin of the underwater gas chromatograph to ensure that the relative humidity of the gas is lower than 5%.

[0012] Furthermore, the tube wall of the inner tube is a water exchange membrane, which only allows water molecules to be exchanged but not gas exchange; the water exchange membrane is a hollow tubular membrane composed of a perfluorosulfonic acid-based polymer.

[0013] Furthermore, the tube wall of the outer tube is a supporting material, including any one of polypropylene, PTFE, PEEK, stainless steel, and aluminum alloy.

[0014] Furthermore, the flow limiter is a thin inner diameter tube or a needle valve, which is used to ensure that when the air pump is turned on, the flow rate of the gas in the outer tube is within the range of 0.1 to 3 L / min, and the pressure of the gas in the outer tube is lower than the pressure of the gas in the inner tube.

[0015] Furthermore, the dryer is a breathable bag filled with a desiccant, the desiccant is a molecular sieve, color-changing silica gel, anhydrous calcium chloride or anhydrous magnesium perchlorate, and the breathable bag material is a non-woven fabric.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The online water removal device for membrane-injected underwater gas chromatograph provided by the present invention can reduce the relative humidity of the injected gas to below 5%, effectively preventing the high-humidity sample gas from damaging the enrichment filler and chromatographic stationary phase in the instrument, and prolonging the working life of the underwater gas chromatograph. At the same time, it can also improve the retention time shift, separation decrease, and water peak covering the chromatographic peak of the target component caused by a large amount of water entering the chromatographic column, and improve the accuracy of qualitative and quantitative analysis.

[0018] 2. The online water removal device for membrane sampling underwater gas chromatograph provided by the present invention uses a casing containing a water exchange membrane as a tube core to exchange the moisture in the injection gas into the dry ambient gas in the instrument cabin. The sample gas does not directly flow through the desiccant, and the components to be tested therein will not be adsorbed. There is no injection discrimination effect for nitrogen, oxygen, carbon dioxide, low-carbon hydrocarbons, aromatic hydrocarbons, etc.

[0019] 3. The online water removal device for membrane sampling underwater gas chromatograph provided by the present invention fully utilizes the characteristics of the closed instrument cabin of the underwater gas chromatograph, and utilizes the cabin gas dried by the desiccant placed in the closed instrument cabin as the drying gas. Therefore, a large amount of desiccant (>kg) can be loaded, and it has an extremely high drying capacity and an extremely long service life. It does not directly absorb moisture in the sample through the desiccant, and the flow path will not be blocked due to the deterioration and compaction of the desiccant.

[0020] 4. The on-line water removal device for a membrane-inlet underwater gas chromatograph provided by the present invention has a simple structure, does not require an additional drying gas cylinder, nor does it need to re-modify the original instrument flow path, and can be directly installed in the underwater gas chromatograph.

[0021] 5. The on-line water removal device for a membrane-inlet underwater gas chromatograph provided by the present invention essentially constructs a large drying gas source by using a sealed chamber, so it is also applicable to other underwater in-situ analysis instruments with a sealed chamber that sample through a water-vapor separation membrane and need to remove water from the sample gas, such as underwater mass spectrometers, underwater semiconductor sensors, underwater infrared sensors, underwater absorption spectrometers, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic diagram of the on-line water removal device for a membrane-inlet underwater gas chromatograph of the present invention.

[0024] Figure 2 It is a comparison diagram of the sampling process before and after installing the water removal device in Embodiments 1 and 2 of the present invention.

[0025] Figure 2 Among them: The solid arrow is the flow direction of the post-membrane sample gas, and the dashed arrow is the flow direction of the drying gas in the chamber.

[0026] Figure 3 It is the chromatogram before and after installing the water removal device in Embodiment 1 of the present invention.

[0027] Figure 3 Among them: The broad peak with a retention time of about 5 - 7 min is the water peak.

[0028] Figure 4 It is the chromatogram before and after installing the water removal device in Embodiment 2 of the present invention.

[0029] Figure 4 Among them: The broad peak with a retention time of about 1.5 - 3.5 min is the water peak.

[0030] In the figure: 101, sleeve; 102, restrictor; 103, air pump; 104, stop valve; 105, dryer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. The description of at least one exemplary embodiment is actually only illustrative and in no way restrictive of the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of the described features, steps, operations, devices, components and / or their combinations.

[0034] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods and devices should be regarded as part of the authorized specification. In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0035] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary description, these orientation terms do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present invention: the orientation terms "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0036] For convenience of description, spatial relative terms such as "above...", "over...", "on the upper surface of...", "above" etc. may be used here to describe the spatial positional relationship of one device or feature shown in the drawings with other devices or features. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "over other devices or structures" will then be positioned "below other devices or structures" or "under other devices or structures". Thus, the exemplary term "above..." can include both the orientation of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the corresponding explanations for the spatial relative descriptions used here will be made.

[0037] In addition, it should be noted that the use of words such as "first", "second", etc. to limit components is only for the convenience of distinguishing the corresponding components. Without otherwise stated, the above words have no special meaning. Therefore, it should not be construed as a limitation on the protection scope of the present invention.

[0038] As Figure 1 shown, the present invention provides an on-line water removal device for a membrane injection underwater gas chromatograph, which is arranged in the internal instrument cabin of the underwater gas chromatograph and includes: a sleeve 101, a restrictor 102, a gas pump 103, a stop valve 104, a dryer 105, and a connecting pipeline, wherein:

[0039] The casing 101 contains a water exchange membrane core and is a double-layer casing, including an inner tube and an outer tube, where: the two end faces of the outer tube are closed tube walls, and there is an opening respectively on the side tube wall of the outer tube near the two end faces; one end of the inner tube is connected to the gas chamber of the membrane injection device of the cut-off valve 104 and the underwater gas chromatograph through a connecting pipeline, and the side opening of the outer tube near this end is connected to the air pump 103 through a connecting pipeline, the other end of the inner tube is connected to the injection pipeline of the cut-off valve 104 and the underwater gas chromatograph through a connecting pipeline, and the side opening of the outer tube near this end is connected to the restrictor 102 and the gas in the internal instrument cabin of the underwater gas chromatograph;

[0040] The air pump 103 and the cut-off valve 104 are respectively connected to the electronic control module of the underwater gas chromatograph, and the switching of the air pump 103 and the cut-off valve 104 is controlled by the electronic control module of the underwater gas chromatograph;

[0041] The dryer 105 is used to maintain the humidity of the gas in the internal instrument cabin of the underwater gas chromatograph to ensure that the relative humidity of the gas is lower than 5%.

[0042] In specific implementation, as a preferred implementation mode of the present invention, the tube wall of the inner tube is a water exchange membrane, and the water exchange membrane only allows the exchange of water molecules and cannot perform gas exchange; the water exchange membrane is a hollow tubular membrane composed of perfluorosulfonic acid-based polymer.

[0043] In specific implementation, as a preferred implementation mode of the present invention, the tube wall of the outer tube is a support material, including any one of polypropylene, PTFE, PEEK, stainless steel, and aluminum alloy.

[0044] In specific implementation, as a preferred implementation mode of the present invention, the restrictor 102 is a thin inner diameter tube or a needle valve, which is used to make the flow rate of the gas in the outer tube within the range of 0.1 - 3 L / min when the air pump 103 is opened, and at the same time, the pressure of the gas in the outer tube is lower than the pressure of the gas in the inner tube.

[0045] In specific implementation, as a preferred implementation mode of the present invention, the dryer 105 is a breathable bag filled with a desiccant, the desiccant is molecular sieve, color-changing silica gel, anhydrous calcium chloride or anhydrous magnesium perchlorate, and the breathable bag material is non-woven fabric.

[0046] The working principle of the device of the present invention is as follows:

[0047] When the underwater gas chromatograph is injecting samples, keep the air pump 103 turned on so that the cabin gas with a relative humidity lower than 5% continuously flows into the outer tube of the sleeve 101. Open the stop valves 104 at both ends. The high-humidity sample in the gas chamber of the membrane injection device of the underwater gas chromatograph passes through the inner tube of the sleeve 101 and enters the injection pipeline of the underwater gas chromatograph. During this process, the water molecules in the high-humidity sample in the inner tube enter the gas in the outer tube with a lower water molecule content through the water exchange membrane of the sleeve 101, so that the relative humidity of the sample gas entering the injection pipeline of the underwater gas chromatograph also drops below 5%. After the injection is completed, turn off the air pump 103 and the stop valves 104.

[0048] Example 1

[0049] This example provides an on-line water removal device for a membrane injection underwater gas chromatograph, including: a sleeve 101, a restrictor 102, an air pump 103, a stop valve 104, a dryer 105, and a connecting pipeline. Among them: the inner wall of the sleeve 101 is made of Nafion117, and the outer wall is made of stainless steel. The restrictor 102 is a PEEK tube with a length of 10 m and an inner diameter of 50 μm. During injection, the gas flow rate in the outer tube is 2 L / min, and the pressure is 30 kPa (absolute pressure). Inside the cabin of the underwater gas chromatograph, there is an approximately 2 kg non-woven bag filled with anhydrous magnesium perchlorate as the dryer 105.

[0050] Install this water removal device between the gas chamber of the membrane injection device of the underwater gas chromatograph and the injection pipeline of the underwater gas chromatograph for in-situ analysis of environmental water. The chromatographic column is a HayesapQ 0.53 mm × 2 m micro-packed column, and the detector is a micro-thermal conductivity detector. The environmental temperature is about 10 °C, and the relative humidity inside the cabin of the underwater gas chromatograph is lower than <1%. The comparison chart of the sampling process before and after installing this water removal device can be seen in Figure 2 The chromatograms before and after installing this water removal device can be seen in Figure 3 .

[0051] From Figure 3 it can be seen that this water removal device significantly reduces the width (from about 2 min to about 0.4 min) and height (from about 7 mV to about 1 mV) of the water peak, verifying the water removal effect of the device of the present invention and being able to improve the problem of the water peak covering the target component; the underwater gas chromatograph installed with this water removal device continuously analyzes for 14 d at intervals of 2 h in environmental water, and the humidity inside the cabin of the underwater gas chromatograph remains unchanged, verifying that the drying capacity of the present invention is extremely large.

[0052] Example 2

[0053] This embodiment provides an on-line water removal device for a membrane injection underwater gas chromatograph, including: a sleeve 101, a restrictor 102, a gas pump 103, a stop valve 104, a dryer 105 and connecting pipelines, where: the inner wall of the sleeve 101 is Nafion 212, and the outer wall is polypropylene. The restrictor 102 is a needle valve. When sampling, the gas flow rate in the outer tube is 0.4 L / min and the pressure is 20 kPa (absolute pressure). Inside the cabin of the underwater gas chromatograph, there is a non-woven bag filled with about 1 kg of 3A molecular sieve as the dryer 105.

[0054] This water removal device is installed between the gas chamber of the membrane injection device of the underwater gas chromatograph and the sampling pipeline of the underwater gas chromatograph for in-situ analysis of environmental water samples added with n-octane. The chromatographic column is a DB-624 0.25 mm×30 m WCOT column, and the detector is a microthermal conductivity detector. The environmental temperature is about 20 °C, and the relative humidity inside the cabin of the underwater gas chromatograph is lower than <5%. The comparison diagrams of the sampling process before and after installing this water removal device are shown in Figure 2 , and the chromatograms before and after installing this water removal device are shown in Figure 4 .

[0055] From Figure 4 it can be seen that this water removal device significantly reduces the width (from about 2 min to about 0.6 min) and peak area (down to about 20%) of the water peak, verifying the water removal effect of the device of the present invention; the peak height of n-octane remains unchanged before and after installation, verifying that the device of the present invention has no injection discrimination; the underwater gas chromatograph installed with this water removal device continuously works 30 times at intervals of 1 h in the environmental water sample added with n-octane, and the relative standard deviation of the retention time of n-octane is lower than 0.5%, and the relative standard deviation of the half-peak width of n-octane is lower than 0.4%, verifying that the present invention can improve the retention time shift and separation degree decline caused by a large amount of water entering the chromatographic column; after continuous analysis for 30 d at intervals of 1 d, the underwater gas chromatograph can still work normally.

[0056] In summary, the present invention uses a sleeve containing a water exchange membrane as a die to exchange the moisture in the sample gas into the dry ambient gas in the instrument cabin, reducing the relative humidity of the sample gas to below 5%, effectively preventing damage to the enrichment packing, chromatographic stationary phase, etc. in the instrument by the high-humidity sample gas, extending the working life of the underwater gas chromatograph, and at the same time improving the problems of retention time shift, decreased resolution, and the water peak covering the chromatographic peaks of target components caused by a large amount of water entering the chromatographic column, and improving the accuracy of qualitative and quantitative analysis. The sample gas does not directly flow through the desiccant, and the components to be measured therein will not be adsorbed. There is no injection discrimination effect for nitrogen, oxygen, carbon dioxide, low-carbon hydrocarbons, aromatics, etc., and the flow path will not be blocked due to the deterioration and caking of the desiccant. The present invention makes full use of the characteristics of the closed instrument cabin of the underwater gas chromatograph and uses the gas in the cabin dried by the desiccant placed in the closed instrument cabin as the drying gas. Therefore, a large amount of desiccant (>kg) can be loaded, having extremely high drying capacity and extremely long service life. The structure of the present invention is simple, without the need for an additional drying gas cylinder, nor the need to re-modify the original instrument flow path, and can be directly installed in the underwater gas chromatograph. In essence, the present invention constructs a very large drying gas source by using the closed cabin, so it is also applicable to other underwater in-situ analysis instruments with closed cabins that sample through a water-gas separation membrane and need to remove water from the sample gas, such as underwater mass spectrometers, underwater semiconductor sensors, underwater infrared sensors, underwater absorption spectrometers, etc.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An on-line water removal device for a membrane injection underwater gas chromatograph, characterized in that, it is arranged in the internal instrument cabin of the underwater gas chromatograph, and includes: a sleeve (101), a flow restrictor (102), an air pump (103), a stop valve (104), a dryer (105), and a connecting pipeline, wherein: The sleeve (101) contains a water exchange membrane core and is a double-layer sleeve, including an inner tube and an outer tube, wherein: the two end faces of the outer tube are closed tube walls, and openings are respectively provided on the side tube walls of the outer tube near the two end faces; one end of the inner tube is connected to the air cavity of the membrane injection device of the underwater gas chromatograph through a connecting pipeline and a stop valve (104), the side opening of the outer tube near this end is connected to the air pump (103) through a connecting pipeline, the other end of the inner tube is connected to the injection pipeline of the underwater gas chromatograph through a connecting pipeline and a stop valve (104), and the side opening of the outer tube near this end is connected to the flow restrictor (102) and the gas in the internal instrument cabin of the underwater gas chromatograph; The air pump (103) and the stop valve (104) are respectively connected to the electronic control module of the underwater gas chromatograph, and the on-off of the air pump (103) and the stop valve (104) is controlled by the electronic control module of the underwater gas chromatograph; The dryer (105) is used to maintain the humidity of the gas in the internal instrument cabin of the underwater gas chromatograph to ensure that the relative humidity of the gas is lower than 5%.

2. The on-line water removal device for a membrane injection underwater gas chromatograph according to claim 1, characterized in that, the tube wall of the inner tube is a water exchange membrane, and the water exchange membrane only allows water molecule exchange and cannot perform gas exchange; the water exchange membrane is a hollow tubular membrane composed of a perfluorosulfonic acid-based polymer.

3. The on-line water removal device for a membrane injection underwater gas chromatograph according to claim 1, characterized in that, the tube wall of the outer tube is a support material, including any one of polypropylene, PTFE, PEEK, stainless steel, and aluminum alloy.

4. The on-line water removal device for a membrane injection underwater gas chromatograph according to claim 1, characterized in that, the flow restrictor (102) is a thin inner diameter tube or a needle valve, which is used to make the flow rate of the gas in the outer tube within the range of 0.1 - 3 L / min when the air pump (103) is opened, and at the same time, the pressure of the gas in the outer tube is lower than the pressure of the gas in the inner tube.

5. The on-line water removal device for a membrane injection underwater gas chromatograph according to claim 1, characterized in that, the dryer (105) is a breathable bag filled with a desiccant, the desiccant is molecular sieve, color-changing silica gel, anhydrous calcium chloride or anhydrous magnesium perchlorate, and the breathable bag material is non-woven fabric.

Images