Gas preconcentrator

Abstract

This application relates to a gas pre-concentrator, belonging to the field of volatile organic compound gas analysis technology, and is mainly used in gas chromatography-mass spectrometry (GC-MS) pretreatment instruments. Related technologies suffer from low concentration efficiency when using the same injection path for both high and low concentration samples. The gas pre-concentrator provided in this application first sends the gas sample into a gas purification cold trap assembly, with the second multi-port switching valve in a second inlet state connected to a negative pressure extraction mechanism. The gas sample is rapidly enriched and concentrated in the gas purification cold trap assembly. After the gas sample in the gas purification cold trap assembly is concentrated to a rated volume, the second multi-port switching valve is in a second sample delivery state, allowing the concentrated gas sample to be passed into a gas focusing peak-shaped cold trap. This further concentrates the purified and concentrated gas sample in the gas focusing peak-shaped cold trap, and the concentrated gas sample is then rapidly passed into the GC-MS instrument, thereby improving detection efficiency.

Description

Technical Field

[0001] This application relates to the field of volatile organic compound gas analysis technology, and in particular to a gas pre-concentrator. Background Technology

[0002] Gas chromatography-mass spectrometry (GC-MS) leverages the excellent separation properties of gas chromatography and the high selectivity of mass spectrometry to achieve qualitative and quantitative determination of complex organic mixtures. Currently, when introducing high- and low-concentration volatile organic compound gases into a GC-MS instrument, the main injection methods include: syringe + screw-in needle + quantitative tube; syringe + high-pressure rotary valve; main pump or auxiliary pump injection; and solid adsorption injection. Among these, syringe + screw-in needle + quantitative tube is the most economical and is commonly used in laboratories, while factories often use main pumps or auxiliary pumps for injection.

[0003] However, when gas chromatography-mass spectrometry (GC-MS) instruments simultaneously inject high- and low-concentration volatile organic compound gas samples, if the high- and low-concentration samples are injected using the same route, the low-concentration sample will require a significant amount of time for pre-concentration, resulting in wasted time and low detection efficiency for both high- and low-concentration volatile organic compound gases. Summary of the Invention

[0004] To improve the detection efficiency of volatile organic compound gases, this application provides a gas pre-concentrator.

[0005] The gas pre-concentrator provided in this application adopts the following technical solution.

[0006] A gas pre-concentrator, comprising:

[0007] A sample gas supply mechanism is used to store multiple sets of different test samples. The sample gas supply mechanism includes an internal standard gas supply component for introducing internal standard gas into the gas pre-concentrator and the gas chromatograph-mass spectrometer to compensate for changes in different concentrations in the gas sample.

[0008] The sample concentration mechanism is connected to the sample gas supply mechanism. The sample concentration mechanism is equipped with a gas impurity removal cold trap group for removing carbon dioxide and moisture from the gas sample and concentrating the gas sample, and a gas focusing peak-shaped cold trap for further concentrating the gas sample and rapidly passing the concentrated gas sample into the gas chromatograph-mass spectrometer.

[0009] A negative pressure extraction mechanism is connected to the sample concentration mechanism to extract gas from the sample gas supply mechanism into the sample concentration mechanism;

[0010] A second multi-way switching valve connects the gas impurity removal cold trap assembly and the gas focusing peak-shaped cold trap. The second multi-way switching valve has a second inlet state connecting the gas impurity removal cold trap assembly and the negative pressure extraction mechanism, and a second sample delivery state for introducing the concentrated gas sample into the gas focusing peak-shaped cold trap. The gas focusing peak-shaped cold trap includes a third cold trap shell, inside which is a third freezing chamber for containing a freezing medium. The third freezing chamber is provided with a compound channel for the flow of high and low concentration volatile organic compound gases and a heating channel for the flow of a preheating medium. The compound channel is located inside the heating channel. The third freezing chamber can simultaneously cool the compound channel and the heating channel.

[0011] By adopting the above technical solution, the internal standard gas supply component first introduces internal standard gas into the sample concentration mechanism to compensate for changes in different concentrations in the gas sample. After the internal standard loading is completed, the sample gas supply mechanism introduces the test sample into the sample concentration mechanism, and the negative pressure extraction mechanism draws the gas from the sample gas supply mechanism into the sample concentration mechanism. First, the gas sample enters the gas purification cold trap group, and the second multi-way switching valve is in the second inlet state connected to the negative pressure extraction mechanism. The gas sample is rapidly enriched and concentrated in the gas purification cold trap group. After the gas sample in the gas purification cold trap group is concentrated to the rated amount, the second multi-way switching valve is in the second sample delivery state, introducing the concentrated gas sample from the gas purification cold trap group into the gas focusing peak-shaped cold trap. This allows the purified and concentrated gas sample to be further concentrated in the gas focusing peak-shaped cold trap and then rapidly introduced into the gas chromatograph-mass spectrometer. Before simultaneously injecting high- and low-concentration volatile organic compound (VOC) gas samples into a gas chromatography-mass spectrometry (GC-MS) instrument, the high- and low-concentration VOC gases are first introduced into the compound channels of the gas focusing peak-shaped cold trap. The samples are then frozen using the freezing medium inside the third freezing chamber. Since the compound channels are located inside the heating channels, after freezing, the frozen samples are rapidly heated through the heating channels, quickly desorbing the VOCs within the compound channels and transferring them to the chromatographic column in the gas chromatograph. This desorption of all VOCs results in high, sharp, and completely separated peaks in the GC-MS sample, without tailing, and with high data validity. The gas purification cold trap assembly and the gas focusing peak-shaped cold trap enable rapid concentration of gas samples, thereby improving the detection efficiency of VOC gases.

[0012] Optionally, the gas focusing peak-shaped cold trap further includes a heat conduction tube, a heat distribution tube disposed within the heat conduction tube, and a third compound tube disposed within the heat distribution tube, wherein the compound channel is formed within the third compound tube, and the heating channel is formed between the heat distribution tube and the heat conduction tube.

[0013] By adopting the above technical solution, the heat distribution tube is set inside the heat conduction tube, and the third compound tube is set inside the heat distribution tube, thereby achieving a uniform diameter of the compound channel and a uniform distance between the heating channel and the compound channel. This ensures that the frozen compound is heated uniformly during the rapid heating of the sample in the compound channel by the heating channel, and the peak shape of the decomposed sample is more stable.

[0014] Optionally, the gas purification cold trap assembly includes a gas dehydration cold trap connected to the sample gas supply mechanism and a gas decarbonation cold trap connected to the second multi-way switching valve. A first multi-way switching valve is connected between the gas dehydration cold trap and the gas decarbonation cold trap. The first multi-way switching valve has a first gas inlet state connected to the negative pressure extraction mechanism and a first sample delivery state that introduces the gas sample concentrated by the gas dehydration cold trap into the gas decarbonation cold trap.

[0015] By adopting the above technical solution, the gas dehydration cold trap comprises two parts: a gas dehydration cold trap connected to the sample gas supply mechanism and a gas decarbon dioxide cold trap connected to the second multi-way switching valve. When the first multi-way switching valve is in the first gas inlet state, the negative pressure extraction mechanism draws the gas sample from the sample gas supply mechanism into the gas dehydration cold trap for dehydration and concentration; when the first multi-way switching valve is in the first sample delivery state, the negative pressure extraction mechanism draws the concentrated gas sample from the gas dehydration cold trap into the gas decarbon dioxide cold trap for further impurity removal and concentration, thereby improving the gas sample concentration and concentration efficiency step by step.

[0016] Optionally, the gas dehydration cold trap includes a first cold trap shell and a first compound tube. The first cold trap shell is provided with a first freezing chamber for containing a freezing medium. The first freezing chamber can cool the first compound tube. The first compound tube passes through the first cold trap shell and extends into the first freezing chamber. The first freezing chamber is also provided with a heating support component for heating the first compound tube.

[0017] By employing the above technical solution, before introducing volatile organic compound (VOC) gas samples into the gas chromatography-mass spectrometry (GC-MS) instrument, the VOC gas sample is first introduced into the first compound tube of the gas dehydration cold trap. The freezing medium in the first freezing chamber condenses and captures all VOCs, water, and carbon dioxide in the sample. After a predetermined condensation time, the first compound tube is heated by a heating support assembly. During the desorption of VOCs, the different vapor pressures of VOCs and water are utilized, retaining water in the gas dehydration cold trap and then desorbing all the desired VOCs. This improves the problem of no data results for polar organic compounds on the GC-MS, and data deviation from the true values, caused by the sample dehydration process.

[0018] Optionally, the gas decarbon dioxide cold trap includes a second cold trap shell and a second compound tube. The second cold trap shell has a second freezing chamber for containing a freezing medium. The second freezing chamber can cool the second compound tube. The second compound tube passes through the second cold trap shell and extends into the second freezing chamber. The second freezing chamber is also provided with a heating component for heating the second compound tube. The second compound tube is also filled with an organic adsorbent for adsorbing volatile organic compounds but not absorbing moisture and carbon dioxide.

[0019] By adopting the above technical solution, organic adsorbents are used to adsorb volatile organic compounds. The characteristic of organic adsorbents is that they do not absorb water and carbon dioxide but have a strong adsorption capacity for volatile organic compounds. Therefore, this gas dehydration cold trap does not need to work in a cryogenic environment. At this temperature, carbon dioxide is not condensed but is directly discharged, thereby improving the carbon dioxide removal capacity of the gas dehydration cold trap.

[0020] Optionally, the sample gas supply mechanism includes an autosampler for accommodating and supplying various gas samples, multiple sample valves connected to the autosampler for controlling the switching of each injection channel, and a first multi-port valve for summing the gas from each injection channel and outputting it from one outlet.

[0021] By adopting the above technical solution, the autosampler can accommodate a variety of different gas samples, improving the testing flexibility of the gas pre-concentrator. Multiple sample valves can control the opening and closing of each sample inlet channel. The gas from each sample inlet channel is collected through the first multi-port connecting valve and then output from a single outlet, thus achieving unattended sample injection operation with simple operation.

[0022] Optionally, the outlet of the first multi-port valve is sequentially connected to a filter for primary filtration of the sample gas and a metering loop for limiting the flow rate of the sample gas introduced by the autosampler into the sample concentration mechanism.

[0023] By adopting the above technical solution, the filter is used for primary filtration of the sample gas. Since each cold trap is saturated, the quantitative loop can limit the flow rate of the sample gas introduced into the sample concentration mechanism by the autosampler, thereby improving the problem of test deviation caused by the cold trap exceeding the saturation state.

[0024] Optionally, the negative pressure extraction mechanism includes a vacuum pump for leak testing, vacuuming, sample injection, transfer, and purging of the pipeline of the gas pre-concentrator; a normally closed vent valve for cleaning the pipeline of the gas pre-concentrator; and a second multi-way connecting valve that simultaneously connects the sample concentration mechanism, the vent valve, and the vacuum pump.

[0025] By adopting the above technical solution, the vacuum pump controls the gas flow in the sample concentration mechanism through the second multi-way connecting valve. When the gas pre-concentrator needs to be tested for leaks, vacuumed, sampled, transferred, and the pipeline purged, the vent valve works in conjunction with the vacuum pump to achieve the main power function.

[0026] Optionally, the sample gas supply mechanism further includes a cleaning gas supply component, which is used to clean the residual gas sample in the internal pipeline of the entire gas pre-concentrator. The cleaning gas supply component includes a cleaning injector for holding nitrogen and a nitrogen valve connecting the cleaning injector to the inlet of the first multi-way connecting valve. A needle valve for controlling the opening and closing of the cleaning injector is connected between the nitrogen valve and the cleaning injector.

[0027] By adopting the above technical solution, when it is necessary to clean the internal pipeline of the entire gas pre-concentrator, first open the needle valve to allow the nitrogen gas in the cleaning injector to flow out, and then open the nitrogen valve to introduce nitrogen gas into the internal pipeline of the entire gas pre-concentrator, thereby completing the cleaning of the internal pipeline of the entire gas pre-concentrator.

[0028] Optionally, the sample concentration mechanism further includes a cold trap short-circuit valve, which connects the first multi-way valve to the inlet of the gas decarbonization cold trap.

[0029] By adopting the above technical solution, when the gas dehydration cold trap is not required for a specific gas sample, the gas in the sample gas supply mechanism can be directly introduced into the gas decarbonation cold trap by opening the cold trap short-circuit valve, thereby improving the flexibility of the gas pre-concentrator.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] 1. High concentration efficiency. First, the gas sample enters the gas purification cold trap assembly, and the second multi-way switching valve is in the second inlet state connected to the negative pressure extraction mechanism. The gas sample is rapidly enriched and concentrated in the gas purification cold trap assembly. After the gas sample in the gas purification cold trap assembly is concentrated to the rated volume, the second multi-way switching valve is in the second sample delivery state, which feeds the concentrated gas sample into the gas focusing peak-shaped cold trap. This allows the purified and concentrated gas sample to be further concentrated in the gas focusing peak-shaped cold trap and then rapidly fed into the gas chromatograph-mass spectrometer. The gas dehydration cold trap consists of two parts: a gas dehydration cold trap connected to the sample gas supply mechanism and a gas decarbon dioxide cold trap connected to the second multi-way switching valve. When the first multi-way switching valve is in the first air intake state, the negative pressure extraction mechanism draws the gas sample from the sample supply mechanism into the gas dehydration cold trap for dehydration and concentration; when the first multi-way switching valve is in the first sample delivery state, the negative pressure extraction mechanism draws the concentrated gas sample from the gas dehydration cold trap into the gas decarbonation cold trap for further impurity removal and concentration, so as to improve the gas sample concentration and concentration efficiency step by step.

[0032] 2. Unattended operation and simple to use. The autosampler can accommodate a variety of different gas samples, improving the testing flexibility of the gas pre-concentrator. Multiple sample valves can control the opening and closing of each injection channel. The gas from each injection channel is collected through the first multi-port valve and then output from a single outlet, thus achieving automatic injection.

[0033] 3. Wide applicability to both high and low concentrations. This gas pre-concentrator has a built-in quantitative loop, achieving a concentration rate of over 1000 times, meeting the sample introduction requirements for high-concentration sample analysis, effectively improving the detection limit of the analytical instrument, and its accuracy is superior to national standards.

[0034] 4. Stable operation and intelligent baking. The gas path configuration is more diverse, flexible, and versatile, better adapting to more advanced analytical methods. Furthermore, it offers greater precision and rationality in gas path switching and time control. The rich gas path variations and precise control significantly improve the instrument's accuracy. Attached Figure Description

[0035] Figure 1 This is an overall schematic diagram of the gas pre-concentrator in the embodiments of this application;

[0036] Figure 2 This is a schematic diagram of the sample concentration mechanism after the first multi-way switching valve switches from the first air intake state (state A) to the first sample delivery state (state B) in the embodiments of this application.

[0037] Figure 3This is a schematic diagram of the sample concentration mechanism after the second multi-way switching valve switches from the second air intake state (state A) to the second sample delivery state (state B) in the embodiments of this application.

[0038] Figure 4 This is a schematic cross-sectional view of the gas dehydration cold trap in an embodiment of this application;

[0039] Figure 5 This is a schematic diagram of the structure of the heating support component in an embodiment of this application;

[0040] Figure 6 This is a schematic diagram of the overall cross-sectional structure of the gas focusing peak-shaped cold trap in the embodiments of this application;

[0041] Figure 7 This is a cross-sectional view of the third cold trap pipe in the embodiment of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 7. Sample gas supply mechanism; 71. Automatic sampler; 72. Sample valve; 73. First multi-way connection valve; 74. Filter; 75. Metering loop; 76. Three-way branch valve; 77. Internal standard gas supply assembly; 771. Internal standard injector; 772. Internal standard valve; 78. Cleaning gas supply assembly; 781. Cleaning injector; 782. Needle valve; 783. Nitrogen valve; 8. Sample concentration mechanism; 81. Heating furnace; 82. Cold trap short-circuit valve; 83. First multi-way connection valve; 100. Liquid nitrogen valve for a cold trap; 110. Gas dehydration cold trap; 111. First cold trap outer shell; 112. First freezing chamber; 113. First cold trap bottom shell; 114. First annular sealing groove; 115. First cold trap top cover; 116. Temperature controller; 117. First heat insulation base plate; 120. First compound tube; 121. First extension portion; 122. First cooling portion; 130. Heating support assembly; 131. Fixing plate; 132. Heating rod; 133. Heat-spreading asbestos layer; 134. Fixing block; 84. First multi-way switching valve; 85. Second cold trap liquid nitrogen valve; 200. Gas decarbonization cold trap; 86. Second multi-way switching valve; 87. Third cold trap liquid nitrogen valve; 300. Gas focusing peak-shaped cold trap; 310. Third cold trap outer shell; 311. Third freezing chamber; 312. Third cold trap bottom shell; 3121. Third annular sealing groove; 313. Third cold trap top cover; 314. Third Insulated base plate; 320, Third cold trap pipe; 321, Heat conduction pipe; 322, Heat distribution pipe; 323, Third compound pipe; 324, Third extension section; 325, Third cooling section; 330, Air blowing valve; 88, Gas chromatograph gas supply port; 89, GC-MS transmission line; 9, Negative pressure extraction mechanism; 91, Vacuum pump; 92, Vent valve; 93, Second multi-way connection valve; 94, Flow meter; 95, Sensor; 96, Flow valve. Detailed Implementation

[0044] The present application will be further described in detail below with reference to the accompanying drawings.

[0045] This application discloses a gas pre-concentrator.

[0046] Figure 1 The schematic diagram of the gas pre-concentrator is shown. The gas pre-concentrator includes a sample gas supply mechanism 7, a sample concentration mechanism 8, and a negative pressure extraction mechanism 9. The sample gas supply mechanism 7 is used to store multiple sets of different test samples. The sample concentration mechanism 8 is connected to the sample gas supply mechanism 7 to remove impurities and concentrate the gas sample in the sample gas supply mechanism 7. The negative pressure extraction mechanism 9 acts as a pneumatic power source and is connected to the sample concentration mechanism 8 to draw gas from the sample gas supply mechanism 7 into the sample concentration mechanism 8.

[0047] The following provides a detailed explanation of each of the three organizations mentioned above.

[0048] Reference Figure 1 The sample gas supply mechanism 7 includes a multi-channel autosampler 71, multiple sample valves 72, a first multi-port connecting valve 73, a filter 74, a metering loop 75, and a three-way branch valve 76 connected in sequence. The multi-channel autosampler 71 can be selected according to the sample type. In this embodiment, a 16-channel autosampler 71 is used. The autosampler 71 and four sample valves 72 are connected in parallel to form four injection channels, enabling unattended automatic injection of multiple gas samples and improving injection efficiency. The first multi-port connecting valve 73 is a 7-way valve with one outlet and six inlets. The inlets of the first multi-port connecting valve 73 are simultaneously connected to the outlets of the four sample valves 72, and the outlets of the first multi-port connecting valve 73 are sequentially connected to the filter 74, the metering loop 75, and the three-way branch valve 76, so that the first multi-port connecting valve 73 can collect the gas from each injection channel and output it from a single outlet. Filter 74 is used for primary filtration of the sample gas, and three-way diverter valve 76 can divert the outlet gas of the first multi-way connecting valve 73 according to instructions. Since the sample concentration mechanism 8 is in a saturated state, the metering loop 75 can limit the flow rate of sample gas introduced into the sample concentration mechanism 8 by the autosampler 71, thereby improving the problem of test deviation caused by the sample concentration mechanism 8 exceeding the saturation state.

[0049] Reference Figure 1To address variations in gas sample concentration and mitigate detection biases caused by different concentrations, the sample gas supply mechanism 7 also includes an internal standard gas supply component 77. This component introduces internal standard gas into the sample concentration mechanism 8 before gas sample concentration to compensate for variations in gas sample concentration. The internal standard gas is a suitable pure standard compound added to the sample during quantitative gas analysis; its measured value serves as a reference for calculating the content of the analyte. The internal standard gas supply component 77 includes an internal standard injector 771 for containing the internal standard gas and an internal standard valve 772 connecting the injector 771 to the inlet of the first multi-port valve 73. The loading of the internal standard is controlled by opening and closing the valve 772. After loading, the sample gas supply mechanism 7 introduces the test sample into the sample concentration mechanism 8, and the negative pressure extraction mechanism 9 draws the gas from the supply mechanism 7 into the concentration mechanism 8.

[0050] Reference Figure 1 After the sample concentration mechanism 8 completes the impurity removal and concentration process for a set of samples, the entire internal pipeline of the gas pre-concentrator needs to be cleaned to facilitate the processing of the next set of samples. Therefore, the sample gas supply mechanism 7 also includes a cleaning gas supply component 78, which is used to purge residual gas samples by introducing nitrogen into the entire internal pipeline of the gas pre-concentrator. The cleaning gas supply component 78 includes a cleaning injector 781 for holding nitrogen and a nitrogen valve 783 connecting the cleaning injector 781 to the inlet of the first multi-way connecting valve 73. A needle valve 782 for controlling the opening and closing of the cleaning injector 781 is connected between the nitrogen valve 783 and the cleaning injector 781. When the entire internal pipeline of the gas pre-concentrator needs to be cleaned, the needle valve 782 is first opened to allow the nitrogen in the cleaning injector 781 to flow out, and then the nitrogen valve 783 is opened to introduce nitrogen into the entire internal pipeline of the gas pre-concentrator.

[0051] Reference Figure 1 The sample concentration mechanism 8 mainly includes a heating furnace 81, a gas purification cold trap assembly, a gas focusing peak-shaped cold trap 300, a first multi-way switching valve 84, and a second multi-way switching valve 86. The heating furnace 81 is mainly used to heat the first multi-way switching valve 84 and the second multi-way switching valve 86 to reduce their adsorption and residue. The gas purification cold trap assembly is used to remove carbon dioxide and moisture from the gas sample and concentrate the gas sample. The gas focusing peak-shaped cold trap 300 is used to further concentrate the gas sample and rapidly pass the concentrated gas sample into the gas chromatograph-mass spectrometer. The first multi-way switching valve 84 and the second multi-way switching valve 86 are used for selective switching connections of the pipelines in the sample concentration mechanism 8. Detailed descriptions follow.

[0052] Reference Figure 1The first multi-way switching valve 84 has ports 1-6 and can operate in a first air intake state (state A) and a first sample delivery state (state B). When the first multi-way switching valve 84 is in the first air intake state, ports 1 and 6 are connected, ports 2 and 3 are connected, and ports 4 and 5 are connected; when the first multi-way switching valve 84 is in the first sample delivery state, ports 1 and 2 are connected, ports 3 and 4 are connected, and ports 5 and 6 are connected. Similarly, the second multi-way switching valve 86 has ports 1-6 and can operate in a second air intake state (state A) and a second sample delivery state (state B). When the second multi-way switching valve 86 is in the second air intake state, ports 1 and 6 are connected, ports 2 and 3 are connected, and ports 4 and 5 are connected; when the second multi-way switching valve 86 is in the second sample delivery state, ports 1 and 2 are connected, ports 3 and 4 are connected, and ports 5 and 6 are connected.

[0053] Reference Figure 1 The gas purification cold trap assembly includes a gas dehydration cold trap 100 and a gas carbon dioxide removal cold trap 200. When sample gas needs to be introduced into the gas dehydration cold trap 100, the first multi-way switching valve 84 is in the first inlet state. At this time, one outlet of the three-way branch valve 76 is connected to port 1 of the first multi-way switching valve 84, port 6 of the first multi-way switching valve 84 is connected to the inlet of the gas dehydration cold trap 100, the outlet of the gas dehydration cold trap 100 is connected to port 3 of the first multi-way switching valve 84, and port 2 of the first multi-way switching valve 84 is connected to the negative pressure extraction mechanism 9, thereby ensuring that the gas dehydration cold trap 100 quickly removes impurities and concentrates the gas sample.

[0054] When the gas sample in the gas dehydration cold trap 100 reaches the required concentration level, refer to Figure 2 The first multi-way switching valve 84 switches from the first gas inlet state to the first sample delivery state. At this time, the three-way branch valve 76 closes to stop the sample delivery, and the original gas inlet of the gas dehydration cold trap 100 becomes the gas outlet and is connected to port 6 of the first multi-way switching valve 84. At this time, ports 5 and 6 of the first multi-way switching valve 84 are connected. Port 5 of the first multi-way switching valve 84 is connected to the gas decarbonation cold trap 200 through the second multi-way switching valve 86, so that the gas sample that has been purified and concentrated by the gas dehydration cold trap 100 is drawn into the gas decarbonation cold trap 200 for further purification and concentration, so as to improve the gas sample concentration and concentration efficiency in steps.

[0055] Reference Figure 2When a purified and concentrated gas sample needs to be introduced into the gas decarbonation cold trap 200, the second multi-way switching valve 86 is in the second inlet state. At this time, port 5 of the first multi-way switching valve 84 is connected to port 1 of the second multi-way switching valve 86, port 6 of the second multi-way switching valve 86 is connected to the inlet of the gas dehydration cold trap 100, the outlet of the gas dehydration cold trap 100 is connected to port 3 of the second multi-way switching valve 86, and port 2 of the second multi-way switching valve 86 is connected to the negative pressure extraction mechanism 9, so that the gas dehydration cold trap 100 quickly purifies and concentrates the gas sample.

[0056] When the gas sample in the gas decarbonization cold trap 200 reaches the required concentration level, refer to... Figure 3 The second multi-way switching valve 86 switches from the second inlet state to the second sample delivery state. The original inlet of the gas decarbon dioxide cold trap 200 becomes the outlet and is connected to port 6 of the second multi-way switching valve 86. At this time, ports 5 and 6 of the second multi-way switching valve 86 are connected. Port 5 of the second multi-way switching valve 86 is connected to the gas focusing peak cold trap 300, so that the gas sample that has been purified and concentrated by the gas decarbon dioxide cold trap 200 is drawn into the gas focusing peak cold trap 300.

[0057] Reference Figure 3 The second multi-port switching valve 86 has port 4 connected to a gas chromatograph gas supply port 88, which is used to introduce carrier gas into the gas focusing peak-shaped cold trap 300. The role of the carrier gas is to carry the gas sample or the vaporized sample gas together into the chromatographic column at a certain flow rate for separation. The separated components are then loaded into the detector for detection, and finally flow out of the chromatographic system for venting or collection. The carrier gas only acts as a carrier and does not participate in the separation process. The outlet of the gas focusing peak-shaped cold trap 300 is connected to a GC-MS transfer line 89. The outlet of the GC-MS transfer line 89 is connected to the gas chromatograph separation column inlet with a pipe connector. Its main function is to transport all the volatile organic compounds in the gas focusing peak-shaped cold trap 300 to the gas chromatograph separation column at a constant temperature of 100 degrees Celsius for separation. After impurity removal and concentration, the gas sample is further concentrated in a gas focusing peak-shaped cold trap 300, and the concentrated gas sample is rapidly passed into a gas chromatograph-mass spectrometer. The peak shape in the gas chromatograph-mass spectrometer is high, sharp, completely separated, without tailing, and the data validity is high, thereby improving the problem of weakened response of early peaks and peak overlap caused by diffusion of gas samples.

[0058] Reference Figure 1The sample concentration mechanism 8 also includes a cold trap short-circuit valve 82. The inlet of the cold trap short-circuit valve 82 is connected to the other outlet of the three-way branch valve 76, and the outlet of the cold trap short-circuit valve 82 is connected to port 4 of the first multi-way switching valve 84. Thus, when the first multi-way switching valve 84 is in the first gas inlet state and the second multi-way switching valve 86 is in the second gas inlet state, it connects to the inlet of the gas decarbonation cold trap 200. When the gas dehydration cold trap 100 is not required for a specific gas sample, the cold trap short-circuit valve 82 is opened so that the gas in the sample gas supply mechanism 7 directly enters the gas decarbonation cold trap 200, improving the flexibility of the gas pre-concentrator.

[0059] The following provides a detailed description of the gas dehydration cold trap 100, the gas carbon dioxide removal cold trap 200, and the gas focusing peak-shaped cold trap 300.

[0060] Reference Figure 1 and Figure 4 A gas dehydration cold trap 100 includes a first cold trap shell 110, a first compound tube 120, and a first cold trap liquid nitrogen valve 83. The first cold trap shell 110 is generally hollow and rectangular, with a first freezing chamber 111 for containing a freezing medium. The first freezing chamber 111 can cool the first compound tube 120. In this embodiment, the freezing medium is partially vaporized liquid nitrogen, which is controlled and introduced into the first freezing chamber 111 by the first cold trap liquid nitrogen valve 83. The first compound tube 120 is made of a special 1 / 8″ OD (outside diameter) stainless steel tube. To improve the saturation threshold of the gas dehydration cold trap 100, the interior of the first compound tube 120 is coated with a thin-film silanized coating. The thin-film silanized coating is used to adsorb polar volatile organic compounds, thereby improving the stability and capacity of adsorption for polar volatile organic compounds. The first compound tube 120 passes through the first cold trap shell 110 and extends into the first freezing chamber 111.

[0061] Specifically, refer to Figure 4The first cold trap outer shell 110 includes a first cold trap bottom shell 112 and a first cold trap top cover 113. The first cold trap bottom shell 112 is generally a hollow cuboid structure with an opening at the top. The first cold trap top cover 113 seals over the opening end face of the first cold trap bottom shell 112. Through holes for introducing the freezing medium are provided on opposite sides of the sidewalls of the first cold trap bottom shell 112, thereby forming a first freezing chamber 111 inside the first cold trap bottom shell 112. To improve the sealing between the first cold trap bottom shell 112 and the first cold trap top cover 113, a first annular sealing groove 1121 is provided on the opening end face of the first cold trap bottom shell 112, and an annular sealing gasket (not shown in the figure) is installed in the first annular sealing groove 1121. The first cold trap top cover 113 is pressed against the opening end face of the first cold trap bottom shell 112 by bolts provided along its edge and abuts against the annular sealing gasket, thereby ensuring a seal between the first cold trap bottom shell 112 and the first cold trap top cover 113.

[0062] Reference Figure 4 To separate the first cold trap outer shell 110 from its mounting base, a first thermal insulation base plate 114 is fixedly provided on the side of the first cold trap bottom shell 112 away from the first cold trap top cover 113. The outline of the first thermal insulation base plate 114 is larger than the projection of the first cold trap bottom shell 112 onto the first thermal insulation base plate 114, thereby mitigating the influence of temperatures outside the first cold trap outer shell 110 on the first cold trap outer shell 110 during the cooling process. In this embodiment, the first thermal insulation base plate 114 is made of bakelite material.

[0063] Reference Figure 4 and Figure 5 The first compound tube 120 has a first extension 121 that passes through and extends from the first cold trap outer shell 110, and a first cooling section 122 arranged in a loop to reduce its volume. The first cooling section 122 is disposed within the first freezing chamber 111 and communicates with the first extension 121. In this embodiment, the first cooling section 122 is generally arranged in a "U" shape, thereby reducing the space occupied by the first cooling section 122 within the first cold trap outer shell 110. In other embodiments, the first cooling section 122 can be arranged in a multi-turn spiral loop as needed, thereby increasing the length of the first compound tube 120 within the first freezing chamber 111 and improving the freezing effect.

[0064] Reference Figure 4 and Figure 5To facilitate heating of the first compound tube 120, a heating support assembly 130 is also provided in the first freezing chamber 111 of the first cold trap outer shell 110. The heating support assembly 130 includes a fixing plate 131, a heating rod 132, and a heat-equalizing asbestos layer 133. The fixing plate 131 is fixedly disposed in the bottom shell 112 of the first cold trap, and the heating rod 132 is fixedly installed on the upper surface of the fixing plate 131. To improve heating efficiency, in this embodiment, the number of heating rods 132 is set to two. The first cooling part 122 is arranged around the heating rod 132 to further improve the uniformity of heat transfer from the heating rod 132 to the first compound tube 120. At the same time, to improve the installation stability of the heating rod 132, a fixing block 134 is also provided on the upper surface of the fixing plate 131. The bottom of the fixing block 134 has two fixing grooves that match the outer circumference of the heating rod 132, so that the fixing block 134 can press and fix the heating rod 132 onto the fixing block 134. The heat-equalizing asbestos layer 133 is fitted onto the outer circumferential surface of the heating rod 132, thereby ensuring that the heat transferred from the heating rod 132 to the first compound tube 120 is more uniform, which facilitates the uniform and stable heating of the frozen compound and the more stable peak shape of the decomposed compound.

[0065] Reference Figure 4 Because the gas dehydration cold trap 100 requires strict temperature control during the processing of volatile organic compound gas samples, a temperature controller 1131 is installed on the side of the first cold trap cover 113 away from the heating rod 132. Simultaneously, a temperature probe (not shown in the figure) is installed inside the first cold trap bottom shell 112 to monitor the temperature inside the first compound tube 120. Both the temperature probe and the heating rod 132 are electrically connected to the temperature controller 1131. The temperature controller 1131 adjusts the heating power of the heating rod 132 based on the temperature data from the temperature probe, thereby ensuring a more stable temperature for the gas dehydration cold trap 100.

[0066] The temperature control method for the gas dehydration cold trap 100 is as follows:

[0067] Freezing temperature 0°C to -196°C (standard -80°C);

[0068] Freezing time: 0 to 20 minutes (standard 15 minutes);

[0069] Heating desorption temperature: 0°C to 250°C (standard 230°C);

[0070] Desorption flow rate: 0 ml to 100 ml per minute (standard 20 ml per minute);

[0071] Desorption time: 0 seconds to 3600 seconds (standard 90 seconds);

[0072] Baking temperature: 0°C to 250°C (standard 240°C);

[0073] The cleaning flow rate is 0 ml to 100 ml per minute (standard 100 ml per minute). The cleaning flow rate is the gas flow rate in the gas dehydration cold trap 100 that removes all the volatile organic compounds required for desorption and cleaning and discharges impurities.

[0074] Cleaning time is 0 seconds to 3600 seconds (standard 240 seconds). The cleaning time is the time required to desorb all the volatile organic compounds and clean and remove impurities from the gas dehydration cold trap 100.

[0075] Purge flow rate: 0 ml to 100 ml per minute (standard 100 ml per minute);

[0076] Purging time: 0 seconds to 3600 seconds (standard 30 seconds);

[0077] The constant temperature range for both cold and hot is 0~50 degrees Celsius (standard 5 degrees Celsius).

[0078] Cold / hot temperature control time: 0 seconds to 3600 seconds (standard 10 seconds).

[0079] The operating principle of the gas dehydration cold trap 100 is as follows: Before the volatile organic compound (VOC) gas sample is introduced into the gas chromatograph-mass spectrometer (GC-MS), the VOC gas sample is first passed into the first compound tube 120 of the gas dehydration cold trap 100. The freezing medium in the first freezing chamber 111 condenses and captures all the VOCs, water, and carbon dioxide in the sample. After a rated condensation time, the first compound tube 120 is heated by the heating support component 130. During the desorption of VOCs, the different vapor pressures of VOCs and water are utilized to retain water in the gas dehydration cold trap 100, and then all the required VOCs are desorbed. This improves the problem of no data results for polar organic compounds on the GC-MS and data deviation from the true values ​​caused by the sample dehydration process.

[0080] Reference Figure 1 and Figure 4The gas decarbon dioxide cold trap 200 has a similar structure to the gas dehydration cold trap 100, but differs in that it has a second compound tube inside. This second compound tube is filled with an organic adsorbent that adsorbs volatile organic compounds but does not absorb moisture or carbon dioxide. The organic adsorbent is a mixture of a linear polymer of poly(2,6-diphenyl-p-phenyl ether) and activated carbon. Both ends of the second compound tube are sealed with 5mm long, 0.5g glass wool. The organic adsorbent does not absorb moisture or carbon dioxide but has a strong adsorption capacity for volatile organic compounds. Therefore, the gas decarbon dioxide cold trap 200 does not need to operate in a cryogenic environment; at this temperature, carbon dioxide is not condensed but is directly discharged, thus improving the carbon dioxide removal capacity of the gas dehydration cold trap 100. Other specific structural details are not elaborated here; refer to the structure of the gas dehydration cold trap 100.

[0081] Reference Figure 6 A gas focusing peak-shaped cold trap 300 includes a third cold trap shell 310 and a third cold trap conduit 320, with a portion of the third cold trap conduit 320 located inside the third cold trap shell 310. Specifically, the third cold trap shell 310 includes a third cold trap bottom shell 312 and a third cold trap top cover 313. The third cold trap bottom shell 312 is generally a hollow cuboid structure with an opening at the top. The third cold trap top cover 313 seals over the opening end face of the third cold trap bottom shell 312, thereby forming a third freezing chamber 311 inside the third cold trap bottom shell 312. To improve the sealing between the third cold trap bottom shell 312 and the third cold trap top cover 313, a third annular sealing groove 3121 is provided on the opening end face of the third cold trap bottom shell 312, and an annular sealing gasket (not shown in the figure) is installed in the third annular sealing groove 3121. The third cold trap top cover 313 is pressed against the open end face of the third cold trap bottom shell 312 by bolts provided along the edge and abuts against the annular sealing gasket, thereby ensuring a seal between the third cold trap bottom shell 312 and the third cold trap top cover 313.

[0082] Reference Figure 1 and Figure 6The third cold trap bottom shell 312 has through holes on opposite sides of its sidewalls for introducing the refrigerant. A liquid nitrogen bottle and a third cold trap liquid nitrogen valve 87 are located on the outside of the third cold trap bottom shell 312. In this embodiment, the refrigerant is partially vaporized liquid nitrogen, which is controlled by the third cold trap liquid nitrogen valve 87 and introduced into the third freezing chamber 311. To separate the third cold trap outer shell 310 from its mounting base, a third thermal insulation base plate 314 is fixedly installed on the side of the third cold trap bottom shell 312 away from the third cold trap top cover 313. The outline of the third thermal insulation base plate 314 is larger than the projection of the third cold trap bottom shell 312 onto the third thermal insulation base plate 314, thereby improving the effect of temperatures outside the third cold trap outer shell 310 on the third cold trap outer shell 310 during the cooling process. In this embodiment, the third thermal insulation base plate 314 is made of bakelite material.

[0083] Reference Figure 7 The third cold trap conduit 320 is coaxially configured with a heat conduction pipe 321, a heat distribution pipe 322, and a third compound pipe 323. The heat distribution pipe 322 is coaxially positioned within the heat conduction pipe 321, and the third compound pipe 323 is coaxially positioned within the heat distribution pipe 322, thus achieving a uniform distance between the heat distribution pipe 322 and the third compound pipe 323. A compound channel is formed within the third compound pipe 323, and a heating channel is formed between the heat distribution pipe 322 and the heat conduction pipe 321. The compound channel is used for the flow of high and low concentration volatile organic compound gases, and the heating channel is used for the passage of the preheating medium. Specifically, the preheating medium is preheated nitrogen. The preheated nitrogen is controlled by a blowing valve 330 located outside the gas focusing peak-shaped cold trap 300. By introducing preheated gas between the heat distribution pipe 322 and the heat conduction pipe 321, the heat distribution pipe 322 is uniformly heated.

[0084] Reference Figure 6 The third cold trap conduit 320 has a third extension 324 that passes through and extends from the third cold trap outer shell 310, and a third cooling section 325 that is arranged in a loop to reduce its volume. The third cooling section 325 is disposed within the third freezing chamber 311 and communicates with the third extension 324. In this embodiment, the third cooling section 325 is generally arranged in a "U" shape, thereby reducing the space occupied by the third cooling section 325 within the third cold trap outer shell 310. In other embodiments, the third cooling section 325 can be arranged in a multi-turn spiral loop as needed, thereby increasing the length of the third cold trap conduit 320 within the third freezing chamber 311 and improving the freezing effect.

[0085] The following describes the specific structure of the third cold trap pipe 320 in detail according to the implementation principle of the gas focusing peak-shaped cold trap 300. The third cold trap pipe 320 is composed of a heat conduction pipe 321, a heat distribution pipe 322, and a third compound pipe 323 coaxially fitted together. Before the gas chromatograph-mass spectrometer (GC-MS) simultaneously injects high- and low-concentration volatile organic compound gas samples, the high- and low-concentration volatile organic compound gases are first introduced into the third compound pipe 323 of the gas focusing peak-shaped cold trap 300. The sample is frozen by the freezing medium inside the third freezing chamber 311, thereby consolidating and concentrating the gaseous volatile organic compound gas sample into a solid phase.

[0086] Since the third compound tube 323 is located between the heat distribution tube 322 and the heat conduction tube 321, after freezing, preheated gas is introduced between the heat distribution tube 322 and the heat conduction tube 321. The frozen sample is then rapidly heated through the heat distribution tube 322, causing the volatile organic compounds in the compound channel to be desorbed and transferred to the chromatographic column in the gas chromatograph, thus desorbing all the volatile organic compounds. Because the gas focusing peak-shaped cold trap 300 requires strict control of the specific low and high temperatures during the processing of volatile organic compound gas samples, a temperature probe is used to monitor the temperature inside the third compound tube 323, thereby ensuring that the gas focusing peak-shaped cold trap 300 has a more stable temperature control method.

[0087] The temperature control method for the gas focusing peak-shaped cold trap 300 is as follows:

[0088] Freezing temperature 0°C to -196°C (standard -180°C);

[0089] Freezing time: 0 to 20 minutes (standard 15 minutes);

[0090] Heating desorption time: 0 seconds to 3600 seconds (standard 30 seconds);

[0091] Cleaning time is 0 seconds to 3600 seconds (standard 240 seconds). The cleaning time is sufficient to desorb all the volatile organic compounds required, and to clean and remove impurities from the gas focusing peak-shaped cold trap 300.

[0092] The constant temperature range for both cold and hot is 0~50 degrees Celsius (standard 5 degrees Celsius).

[0093] Cold / hot temperature control time: 0 seconds to 3600 seconds (standard 10 seconds).

[0094] Reference Figure 6To improve the saturation threshold of the gas focusing peak-shaped cold trap 300, the interior of the third compound tube 323 is coated with a thin-film silanized coating. This thin-film silanized coating is used to adsorb polar volatile organic compounds, thereby improving the stability and capacity of adsorption for these compounds. Polarity refers to the non-uniformity of charge distribution within a covalent bond or a covalent molecule. If the charge distribution is non-uniform, the bond or molecule is called polar. Furthermore, if the bending angle of the third compound tube 323 in the third cold trap channel 320 is less than 90 degrees, the thin-film silanized coating will be damaged, which is not conducive to the desorption of volatile organic compounds. Therefore, the third compound tube 323 is arranged in a "U"-shaped loop to ensure that the bending angle at each bend of the third compound tube 323 is uniformly distributed and greater than 90 degrees.

[0095] In this embodiment, the heat conduction tube 321 is made of copper, which is beneficial for the third cold trap tube 320 to quickly absorb the heat of the organic compound gas sample during the freezing process. The heat distribution tube 322 is made of polytetrafluoroethylene (PTFE). Since PTFE is non-polar, heat-resistant, and non-absorbent, and is also an excellent electrical insulating material, it is beneficial for the heat on the outer wall of the heat distribution tube 322 to be more evenly conducted into the third compound tube 323 during the rapid heating of the frozen sample in the heating channel. This facilitates uniform heating of the frozen compound and more stable peak shape of the decomposed sample.

[0096] Reference Figure 1 The negative pressure extraction mechanism 9 includes a vacuum pump 91, a vent valve 92, and a second multi-way connecting valve 93. The vacuum pump 91 is used for leak testing, vacuuming, sample injection, transfer, and pipeline purging of the gas pre-concentrator. The vent valve 92 is normally closed but is opened when cleaning the pipeline of the gas pre-concentrator. The second multi-way connecting valve 93 has three inlets and two outlets. The vacuum pump 91 is connected to a flow meter 94 and to one outlet of the second multi-way connecting valve 93, while the vent valve 92 is connected to the other outlet of the second multi-way connecting valve 93. Port 2 of the first multi-way switching valve 84 is connected to one inlet of the second multi-way connecting valve 93 via a flow valve 96. Port 2 of the second multi-way switching valve 86 is connected to another inlet of the second multi-way connecting valve 93. A sensor 95 is connected to the third inlet of the second multi-way connecting valve 93 to read the pressure changes in the pipeline of the gas pre-concentrator in real time, thereby providing feedback information on different states.

[0097] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the above description refer to directions in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A gas pre-concentrator, characterized in that, include: The sample gas supply mechanism (7) is used to store multiple different sets of test samples. The sample gas supply mechanism (7) includes an internal standard gas supply component (77) for introducing internal standard gas into the gas pre-concentrator and the gas chromatograph-mass spectrometer to compensate for changes in different concentrations in the gas sample. The sample concentration mechanism (8) is connected to the sample gas supply mechanism (7). The sample concentration mechanism (8) is equipped with a gas impurity removal cold trap group for removing carbon dioxide and moisture from the gas sample and concentrating the gas sample, and a gas focusing peak-shaped cold trap (300) for further concentrating the gas sample and quickly passing the concentrated gas sample into the gas chromatograph-mass spectrometer. The negative pressure extraction mechanism (9) is connected to the sample concentration mechanism (8) to extract the gas in the sample gas supply mechanism (7) into the sample concentration mechanism (8); A second multi-way switching valve (86) is connected between the gas impurity removal cold trap group and the gas focusing peak-shaped cold trap (300). The second multi-way switching valve (86) has a second air intake state connecting the gas impurity removal cold trap group and the negative pressure extraction mechanism (9) and a second sample delivery state for introducing the concentrated gas sample into the gas focusing peak-shaped cold trap (300). The gas focusing peak-shaped cold trap (300) includes a third cold trap shell (310). The third cold trap shell (310) is provided with a third freezing chamber (311) for containing the freezing medium. The third freezing chamber (311) is provided with a compound channel for supplying high and low concentration volatile organic compound gases and a heating channel for supplying preheating medium. The compound channel is located inside the heating channel. The third freezing chamber (311) can simultaneously cool the compound channel and the heating channel.

2. The gas pre-concentrator according to claim 1, characterized in that, The gas focusing peak-shaped cold trap (300) further includes a heat conduction tube (321), a heat distribution tube (322) disposed within the heat conduction tube (321), and a third compound tube (323) disposed within the heat distribution tube (322). The compound channel is formed within the third compound tube (323), and the heating channel is formed between the heat distribution tube (322) and the heat conduction tube (321).

3. The gas pre-concentrator according to claim 1, characterized in that, The gas purification cold trap assembly includes a gas dehydration cold trap (100) connected to the sample gas supply mechanism (7) and a gas decarbonation cold trap (200) connected to the second multi-way switching valve (86). A first multi-way switching valve (84) is connected between the gas dehydration cold trap (100) and the gas decarbonation cold trap (200). The first multi-way switching valve (84) has a first air intake state connected to the negative pressure extraction mechanism (9) and a first sample delivery state that introduces the gas sample concentrated by the gas dehydration cold trap (100) into the gas decarbonation cold trap (200).

4. The gas pre-concentrator according to claim 3, characterized in that, The gas dehydration cold trap (100) includes a first cold trap shell (110) and a first compound tube (120). The first cold trap shell (110) is provided with a first freezing chamber (111) for containing a freezing medium. The first freezing chamber (111) can cool the first compound tube (120). The first compound tube (120) passes through the first cold trap shell (110) and extends into the first freezing chamber (111). The first freezing chamber (111) is also provided with a heating support assembly (130) for heating the first compound tube (120).

5. The gas pre-concentrator according to claim 3, characterized in that, The gas decarbon dioxide cold trap (200) includes a second cold trap shell and a second compound tube. The second cold trap shell is provided with a second freezing chamber for containing a freezing medium. The second freezing chamber can cool the second compound tube. The second compound tube passes through the second cold trap shell and extends into the second freezing chamber. The second freezing chamber is also provided with a heating component for heating the second compound tube. The second compound tube is also filled with an organic adsorbent for adsorbing volatile organic compounds but not absorbing moisture and carbon dioxide.

6. The gas pre-concentrator according to claim 3, characterized in that, The sample gas supply mechanism (7) includes an autosampler (71) for accommodating and supplying various different gas samples, multiple sample valves (72) connected to the autosampler (71) for controlling the switching of each injection channel, and a first multi-way valve (73) for summing the gas from each injection channel and outputting it from one outlet.

7. The gas pre-concentrator according to claim 6, characterized in that, The outlet of the first multi-way connection valve (73) is sequentially connected to a filter (74) for primary filtration of the sample gas and a metering loop (75) for limiting the flow rate of the sample gas introduced by the autosampler (71) into the sample concentration mechanism (8).

8. The gas pre-concentrator according to claim 1, characterized in that, The negative pressure extraction mechanism (9) includes a vacuum pump (91) for leak testing, vacuuming, sample injection, transfer and purging of the pipeline of the gas pre-concentrator, a normally closed vent valve (92) for cleaning the pipeline of the gas pre-concentrator, and a second multi-way connecting valve (93) that connects the sample concentration mechanism (8), the vent valve (92) and the vacuum pump (91) simultaneously.

9. The gas pre-concentrator according to claim 1, characterized in that, The sample gas supply mechanism (7) further includes a cleaning gas supply assembly (78), which includes a cleaning injector (781) for holding nitrogen gas and a nitrogen valve (783) connecting the cleaning injector (781) to the inlet of the first multi-way connecting valve (73). A needle valve (782) for controlling the opening and closing of the cleaning injector (781) is connected between the nitrogen valve (783) and the cleaning injector (781).

10. The gas pre-concentrator according to claim 6, characterized in that, The sample concentration mechanism (8) also includes a cold trap short-circuit valve (82), which connects the first multi-way valve (73) to the inlet of the gas decarbonization cold trap (200).

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