Composite thermal desorption air sampling detection method in occupational health field

Abstract

The invention discloses a composite thermal desorption air sampling detection method in the field of occupational health, and belongs to the technical field of thermal desorption. A composite thermal desorption air sampling detection method in the field of occupational health comprises the following steps: S1, screening solid adsorbent materials, namely screening out a plurality of solid adsorbents which can simultaneously adsorb 24 common vapor-state organic toxicants and have different specific surface areas; s2, determining the shape and the material of the composite thermal desorption air sampling tube; s3, treatment of solid adsorbents: preparing the screened solid adsorbent material at high temperature, and sequentially filling a sampling tube with the prepared multiple solid adsorbents; according to the invention, four solid adsorbents with different specific surface areas are assembled into a combined solid adsorbent material according to the sequence of adsorption strength from small to large, 24 common vapor-state organic toxicants can be effectively adsorbed, the adsorption capacity is high, and the penetration phenomenon is not easy to occur.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal desorption, and particularly relates to a composite thermal desorption air sampling and detection method in the field of occupational health. Background Art

[0002] There are a wide variety of organic poisons in the air of workplaces, with different toxicities and large concentration variations. Common organic poisons mainly exist in the form of vapor state in the air of workplaces at normal temperature, such as alkane compounds, alkene compounds, aromatic hydrocarbon compounds, halogenated hydrocarbon compounds, alcohol compounds, ether compounds, ketone compounds, ester compounds, nitrile compounds, etc. These common organic poisons widely exist in environmental media such as air, water, and soil, have relatively high toxicity, can be absorbed through the respiratory tract, digestive tract, and skin. Most organic poisons have irritating effects on the human skin, conjunctiva, and respiratory organs, and some also have carcinogenic effects. There are a large number of occupational exposure people, posing relatively great occupational health hazards.

[0003] Currently, the standard methods in the field of occupational health in China mainly use solvent desorption-gas chromatography to detect common vapor-state organic poisons in the air of workplaces. Activated carbon tubes and silica gel tubes are mainly used for collection. The collected samples need to be treated with different desorbing solutions, which is not conducive to the actual work. Moreover, mainly using highly toxic carbon disulfide as the desorbing solution poses great harm to experimental personnel and the ecological environment.

[0004] In the prior art, the Chinese patent with the application number CN202211521625.3 discloses a new type of sample sampling tube, including a sample tube and an automatic thermal desorption and desorption instrument, and further includes: sealing heads, which are arranged at both ends of the sample tube and are hermetically connected to the sample tube; injection needles, which are connected to the detection end of the automatic thermal desorption and desorption instrument; a sealing structure, which is arranged inside the sealing head for sealing the sealing head and cooperating with the injection needle to facilitate assembly and use and replacement of the sealing gasket. However, in the specific operation process, since the sealing structure only relies on the elastic force of the stable spring to push the sealing gasket against the fixed column to achieve the isolation of the sealing head from the outside, when the elastic force of the stable spring weakens, the sealing effect of the sealing head becomes poor, affecting the thermal desorption detection effect; and when the fixed column slides relative to the sealing gasket, the sealing gasket is easily worn, and it is necessary to disassemble the limit sleeve for replacement, and the operation is relatively cumbersome. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art, and propose a composite thermal desorption air sampling and detection method in the field of occupational health.

[0006] In order to achieve the above purpose, the present invention adopts the following technical scheme:

[0007] A composite thermal desorption air sampling and detection method in the field of occupational health includes the following steps:

[0008] S1: Screening of solid adsorbent materials to screen out multiple solid adsorbents with different specific surface areas that can simultaneously adsorb 24 common vaporous organic poisons.

[0009] S2: Determining the shape and material of the composite thermal desorption air sampling tube.

[0010] S3: Treatment of the solid adsorbent. The selected solid adsorbent materials are prepared by high temperature and the prepared multiple solid adsorbents are successively filled into the sampling tube.

[0011] S4: Sample absorption. The sampling tube is used to adsorb 24 common vaporous organic poisons in the air.

[0012] S5: Sample treatment. The composite thermal desorption air sampling tube is installed on a thermal desorption instrument and heated to desorb the organic vapor from the solid adsorbent and be carried by the carrier gas into the cold trap for preconcentration. The direction of the carrier gas is opposite to the sampling direction, and then it is rapidly desorbed at a low flow rate and enters the capillary gas chromatograph through the transfer line.

[0013] Preferably, the multiple solid adsorbents prepared in step S3 are successively a first graphitized carbon adsorbent layer, a second graphitized carbon adsorbent layer, a third graphitized carbon adsorbent layer, and a carbon molecular sieve adsorbent.

[0014] Preferably, the first graphitized carbon adsorbent layer is a graphitized carbon adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 20 m2 / g, and a mass of 50 - 120 mg; the second graphitized carbon adsorbent layer is a graphitized carbon adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 130 m2 / g, and a mass of 50 - 120 mg; the third graphitized carbon adsorbent layer is a graphitized carbon adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 240 m2 / g, and a mass of 50 - 120 mg; the carbon molecular sieve adsorbent is a carbon molecular sieve adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 1200 m2 / g, and a mass of 50 - 120 mg.

[0015] Preferably, the sampling tube in step S2 includes a tube body and sealing heads arranged at both ends of the tube body. The sealing head includes a first outer shell threadedly connected to the tube body and a second outer shell threadedly connected to the first outer shell. A conical opening is provided at the top of the second outer shell. A support plate is fixedly provided on the inner wall of the first outer shell, and a guide post is fixedly provided on the support plate. A conical plug is slidably connected to the outside of the guide post. An elastic element is arranged between the guide post and the conical plug. A conical surface matching the conical plug is provided on the inner wall of the second outer shell. A first sealing gasket is provided on the conical surface and is in movable abutment with the conical plug. A positioning assembly for positioning the conical plug is provided on the support plate, and an auxiliary sealing assembly for blocking the conical opening is provided on the positioning assembly.

[0016] Preferably, the sampling tube further includes a sampling injection thimble connected to the detection end of the thermal desorption desorber. The sampling injection thimble is movably connected to the conical opening, and a top block that movably abuts against the top of the conical plug is fixedly provided at the bottom of the sampling injection thimble.

[0017] Preferably, the positioning assembly includes an elastic telescopic rod rotatably connected to the support plate. A torsion spring for driving the elastic telescopic rod to reset and rotate is arranged inside the support plate. A positioning block is fixedly provided on the elastic telescopic rod. An arc-shaped groove matching with the positioning block is opened on the conical plug. An extrusion inclined surface is opened at the edge of the top wall of the arc-shaped groove. A sealing bearing is arranged between the elastic telescopic rod and the second outer shell.

[0018] Preferably, a connecting plate is fixedly provided at the telescopic end of the elastic telescopic rod. A guiding plate is fixedly provided on the connecting plate. A top rod that movably abuts against the guiding plate is fixedly provided on the sampling injection thimble.

[0019] Preferably, the auxiliary sealing assembly includes a top plate. The top plate is connected to one end of the connecting plate away from the elastic telescopic rod. A second sealing gasket that movably abuts against the top wall of the second outer shell is fixedly provided at the bottom of the top plate.

[0020] Preferably, a ring is fixedly provided on the second outer shell through a connecting plate. The ring is coaxially arranged with the elastic telescopic rod. A force-bearing inclined surface that movably abuts against the bottom wall of the connecting plate is opened at the top of the ring.

[0021] Preferably, abutting inclined surfaces are opened between the tube body and the first outer shell and between the first outer shell and the second outer shell. A third sealing gasket is arranged on the abutting inclined surface.

[0022] Compared with the prior art, the present invention provides a composite thermal desorption air sampling and detection method in the field of occupational health, having the following beneficial effects:

[0023] 1. In the composite thermal desorption air sampling and detection method in the field of occupational health, by assembling four solid adsorbents with different specific surface areas into a combined solid adsorbent material in the order of increasing adsorption strength, 24 common vaporous organic poisons can be effectively adsorbed, having a high adsorption capacity and not being prone to breakthrough phenomenon.

[0024] 2. In the composite thermal desorption air sampling and detection method in the field of occupational health, when the elastic telescopic rod resets, it drives the positioning block to abut against the extrusion inclined surface of the top wall of the arc-shaped groove. During the reset of the positioning block, it pushes the conical plug to move upward, so that the conical plug moves to the initial position. The first sealing gasket outside the conical plug abuts against the inner wall of the second outer shell. Even when the elastic force of the elastic element weakens, the sealing between the conical plug and the second outer shell can still be ensured, avoiding the leakage of the sample gas in the sampling tube.

[0025] 3. The composite thermal desorption air sampling and detection method in the field of occupational health effectively improves the sealing performance of the sampling tube by setting a top plate and a second sealing gasket to assist in sealing the conical opening. When the injection thimble moves downward, the ejector rod exerts a thrust on the guide plate on the connecting plate, causing the guide plate to drive the connecting plate to rotate around the elastic telescopic rod. While the positioning block releases the restriction on the conical plug, the connecting plate drives the top plate to move and no longer seals the conical opening, thus facilitating the bottom of the injection thimble to enter the conical opening subsequently and ensuring the smooth progress of the detection work.

[0026] 4. In the composite thermal desorption air sampling and detection method in the field of occupational health, when the guide plate drives the connecting plate to rotate around the elastic telescopic rod under force, the connecting plate abuts against the force-receiving inclined surface at the top of the ring. As the connecting plate continues to move, the connecting plate is lifted by the force-receiving inclined surface of the ring, thereby driving the top plate to move upward by the connecting plate. During the movement, the second sealing gasket at the bottom of the top plate reduces the friction with the top wall of the second housing, thus ensuring the service life of the second sealing gasket. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the sealing head of the present invention;

[0028] Figure 2 of the present invention Figure 1 Partial enlarged structural diagram of part A;

[0029] Figure 3 It is a schematic sectional structure diagram of the sealing head of the present invention;

[0030] Figure 4 of the present invention Figure 3 Partial enlarged structural diagram of part B;

[0031] Figure 5 It is a schematic structural diagram of the positioning block placed in the arc-shaped groove of the present invention;

[0032] Figure 6 It is a schematic structural diagram when the injection thimble abuts against the conical plug of the present invention;

[0033] Figure 7 It is a schematic overall structure diagram of the present invention.

[0034] In the figure: 1. Sampling tube; 101. Tube body; 102. Sealing head; 1021. First outer shell; 1022. Second outer shell; 103. Sampling thimble; 1031. Top block; 1032. Thumb rod; 2. Support plate; 201. Guide post; 202. Tapered plug; 2021. Arc groove; 203. Elastic element; 204. First sealing gasket; 3. Tapered opening; 4. Elastic telescopic rod; 401. Positioning block; 402. Sealing bearing; 5. Torsion spring; 6. Connecting plate; 601. Guide plate; 7. Top plate; 701. Second sealing gasket; 8. Ring; 9. Third sealing gasket. Detailed implementation manners

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. 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 protection scope of the present invention.

[0036] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "top / bottom end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "provided with", "sheathed / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0038] Example: Refer to Figure 1-7 , a composite thermal desorption air sampling and detection method in the field of occupational health, including the following steps:

[0039] S1: Screening of solid adsorbent materials, screening out multiple solid adsorbents that can simultaneously adsorb 24 common vapor-state organic poisons and have different specific surface areas;

[0040] S2: Determining the shape and material of the composite thermal desorption air sampling tube 1;

[0041] S3: Treatment of the solid adsorbent. The selected solid adsorbent material is prepared by high temperature, and the prepared multiple solid adsorbents are successively filled into the sampling tube 1.

[0042] S4: Sample absorption. The sampling tube 1 is used to adsorb 24 common vaporous organic poisons in the air.

[0043] S5: Sample treatment. The composite thermal desorption air sampling tube 1 is installed on the thermal desorption instrument and heated to desorb the organic vapor from the solid adsorbent and be carried by the carrier gas into the cold trap for preconcentration. The direction of the carrier gas is opposite to that during sampling. Then, it is rapidly desorbed at a low flow rate and enters the capillary gas chromatograph through the transfer line.

[0044] Further, the multiple solid adsorbents prepared in step S3 are successively the first graphitized carbon adsorbent layer, the second graphitized carbon adsorbent layer, the third graphitized carbon adsorbent layer, and the carbon molecular sieve adsorbent.

[0045] Further, the first graphitized carbon adsorbent layer is a graphitized carbon adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 20 m2 / g, and a mass of 50 - 120 mg; the second graphitized carbon adsorbent layer is a graphitized carbon adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 130 m2 / g, and a mass of 50 - 120 mg; the third graphitized carbon adsorbent layer is a graphitized carbon adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 240 m2 / g, and a mass of 50 - 120 mg; the carbon molecular sieve adsorbent is a carbon molecular sieve adsorbent with a particle size of 20 - 40 mesh, a specific surface area of 1200 m2 / g, and a mass of 50 - 120 mg.

[0046] Specifically, the sampling tube 1 is a cylindrical tube with standard dimensions: a length of 90 mm, an outer diameter of 6.3 mm, and an inner diameter of 5 mm. The material of the sampling tube 1 can be stainless steel or hard glass. The method for filling the solid adsorbent in the composite thermal desorption air sampling tube is as follows: First, place stainless steel wire or silanized glass wool with pores smaller than the particle size of the solid adsorbent (to prevent the solid adsorbent from falling) at the bottom of the sampling tube 1 (i.e., the sampling outlet end), and then sequentially place 50 - 120 mg of carbon molecular sieve adsorbent with a particle size of 20 - 40 mesh and a specific surface area of 1200 m2 / g, 50 - 120 mg of the third graphitized carbon adsorbent with a particle size of 20 - 40 mesh and a specific surface area of 240 m2 / g, 50 - 120 mg of the second graphitized carbon adsorbent with a particle size of 20 - 40 mesh and a specific surface area of 130 m2 / g, and 50 - 120 mg of the first graphitized carbon adsorbent with a particle size of 20 - 40 mesh and a specific surface area of 20 m2 / g (the various solid adsorbents are separated by inert materials such as silanized glass wool, carbon wool, or quartz wool), and then place stainless steel wire or silanized glass wool with pores smaller than the particle size of the solid adsorbent (to prevent the solid adsorbent from falling); finally, put sealing parts on both ends of the sampling tube 1. It should be noted that the position of the solid adsorbent filled in the sampling tube 1 is at least 15 mm away from the sampling inlet end of the sampling tube 1, and the length of the filled solid adsorbent cannot exceed the size of the heating zone of the thermal desorption instrument; the sampling tube 1 should have a sampling air flow direction mark; the filled sampling tube 1 should be subjected to a resistance test. At a flow rate of 0.05 L / min and a long-term sampling of 480 min, the ventilation resistance should be less than 4.0 KPa.

[0047] Furthermore, graphitized carbon adsorbents with different specific surface areas and extremely low backgrounds are formed by graphitizing activated carbon with specific pore sizes at high temperatures (above 3000 °C), and carbon molecular sieve adsorbents with extremely low backgrounds are formed by template activation of molecular sieves with specific pore sizes followed by carbonization at high temperatures (above 1000 °C) to ensure that the prepared different solid adsorbents do not contain the above 24 common vaporous organic poisons or substances that can interfere with the determination of the above 24 common vaporous organic poisons.

[0048] In addition, during sample processing, the composite thermal desorption air sampling tube 1 is installed on the thermal desorption instrument and heated to desorb the organic vapor from the solid adsorbent, which is then carried by the carrier gas into the cold trap for preconcentration. The direction of the carrier gas is opposite to the sampling direction, and then it is rapidly desorbed at a low flow rate and enters the capillary gas chromatograph through the transfer line.

[0049] The sample determination conditions are as follows: Thermal desorption and desorption conditions: Desorption temperature of the sample tube: 300 °C; Desorption time: 10 min; Dry blowing for 1 min; Transfer line temperature: 210 °C; Valve temperature: 200 °C; Trapping trap temperature: Low temperature -30 °C, high temperature 300 °C, heating rate 40 °C / S; Trapping trap desorption time: 7 min; Outlet split flow: 14 ml / min; Inlet split flow: 60 ml / min; Desorption flow rate: 50 mL / min. Chromatographic determination conditions: Detector: Flame ionization detector (FID); Chromatographic column: 60 m × 0.25 mm × 1.00 μm, DB-5MS; Detector temperature: 300 °C; Carrier gas (nitrogen) flow rate: Constant flow rate of 1.0 mL / min; Column temperature: Initial temperature 40 °C, held for 10.00 min, heated to 250 °C at 5 °C / min, held for 4.00 min.

[0050] The technology is assembled into a composite thermal desorption air sampling tube 1 by filling four kinds of solid adsorbents (filled in a mass ratio of 1:1, and the specific surface areas of the solid adsorbents filled from the sampling inlet to the sampling outlet are from small to large). It can effectively collect 24 common vapor-state organic poisons in the workplace air at the same time, including acetonitrile, acrylonitrile, acetone, butanone, cyclohexanone, benzene, toluene, xylene (all isomers), methyl acetate, ethyl acetate, butyl acetate, vinyl acetate, styrene, ethylene glycol butyl ether, n-hexane, dichloromethane, 1,2-dichloroethane, trichloromethane, trichloroethylene, isopropanol, n-butanol, carbon disulfide, etc. When the mass concentration of the above 24 common vapor-state organic toxicants in the workplace air is between 1 and 500 mg / m3, the developed air sampling tube 1 is used to collect samples at 0.20 L / min for 15 minutes, and the short-time sampling efficiency of each target component is 100.0%; when the mass concentration of the above 24 common vapor-state organic toxicants in the workplace air is between 1 and 500 mg / m3, the developed air sampling tube 1 is used to collect samples at 0.05 L / min for 480 minutes, and the long-time sampling efficiency of each target component is greater than 90%, and no penetration phenomenon occurs. The total adsorption capacity of the above 24 common vapor-state organic toxicants is greater than 5 mg. The method measured the above 24 common vapor-phase organic poison mixed standard series gases at a content of 0-500 μg, with correlation coefficients of 0.9992-0.9999, detection limits of 0.003-0.06 μg (calculated at 3 times the standard deviation), quantitative limits of 0.005-0.010 μg (calculated at 10 times the standard deviation), the lowest detection concentration in the air of 0.001-0.002 mg / m3 (based on the collection of 3.0 L of sample), and the lowest quantitative concentration of 0.002-0.0 04mg / m3 (based on the collection of 3.0L samples); the average thermal desorption efficiency is greater than 95%, the accuracy meets the technical requirements between 95% and 105%, and the relative standard deviation of precision is less than 10%; the air sampling tube 1 that collects the above 24 common vapor-state organic toxicants in the workplace air can be stably stored at 4°C for more than 7 days under sealed storage conditions; the interference substances that may coexist in the air of the on-site workplace (such as methyl methacrylate, methyl isobutyl ketone, isophorone, etc.) do not affect the determination. Therefore, the determination method matched with the composite thermal desorption air sampling tube 1 can be used to efficiently and accurately determine the concentration levels of the above 24 common vapor-state organic toxicants in the workplace air. In summary, this technology can simultaneously collect and detect the above 24 common vapor-state organic toxicants in workplace air, greatly improving the accuracy and sensitivity of the method, and can perform simultaneous sampling and detection in any sampling method (individual sampling or fixed-point sampling, long-term sampling or short-time sampling), overcoming the current shortcomings of using different air sampling tubes for collection, different desorption solutions for sample pretreatment, and different detection methods for measurement, greatly improving the sampling and detection efficiency and work quality.Meanwhile, the developed composite thermal desorption air sampling tube 1 can not only be used to collect the above 24 common vaporous organic poisons in workplace air, but also be used to collect other common vaporous organic poisons in workplace air. By optimizing the sample thermal desorption conditions and the detection conditions of the instrument and equipment, a series of supporting qualitative and quantitative determination methods are formed. It is expected to achieve rapid, efficient and comprehensive monitoring of the concentration levels of more common vaporous organic poisons in workplace air, and also provide strong technical support for the effective disposal of sudden chemical poisoning incidents caused by common vaporous organic poisons. Therefore, the research and development of the composite thermal desorption air sampling tube 1 and its supporting determination methods have broad application prospects.

[0051] Referring to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 and Figure 7 , as a preferred technical solution of the present invention, the sampling tube 1 in step S2 includes a tube body 101 and sealing heads 102 provided at both ends of the tube body 101. The sealing head 102 includes a first outer shell 1021 threadedly connected to the tube body 101 and a second outer shell 1022 threadedly connected to the first outer shell 1021. A conical opening 3 is provided at the top of the second outer shell 1022. A support plate 2 is fixedly provided on the inner wall of the first outer shell 1021. A guide post 201 is fixedly provided on the support plate 2. A conical plug 202 is slidably connected to the outside of the guide post 201. An elastic element 203 is provided between the guide post 201 and the conical plug 202. A conical surface matching the conical plug 202 is provided on the inner wall of the second outer shell 1022. A first sealing gasket 204 that is movably abutted against the conical plug 202 is provided on the conical surface. A positioning assembly for positioning the conical plug 202 is provided on the support plate 2. An auxiliary sealing assembly for sealing the conical opening 3 is provided on the positioning assembly.

[0052] Furthermore, the sampling tube 1 further includes a sampling injection thimble 103 connected to the detection end of the thermal desorption desorber. The sampling injection thimble 103 is movably connected at the conical opening 3. A top block 1031 that is movably abutted against the top of the conical plug 202 is fixedly provided at the bottom of the sampling injection thimble 103.

[0053] Furthermore, the positioning assembly includes an elastic telescopic rod 4 rotatably connected to the support plate 2. A torsion spring 5 for driving the elastic telescopic rod 4 to reset and rotate is provided inside the support plate 2. A positioning block 401 is fixedly provided on the elastic telescopic rod 4. An arc-shaped groove 2021 matching the positioning block 401 is provided on the conical plug 202. An extrusion inclined surface is provided at the top wall edge of the arc-shaped groove 2021. A sealing bearing 402 is provided between the elastic telescopic rod 4 and the second outer shell 1022.

[0054] Furthermore, a connecting plate 6 is fixedly arranged at the telescopic end of the elastic telescopic rod 4, a guiding plate 601 is fixedly arranged on the connecting plate 6, and a top rod 1032 which is movably abutted against the guiding plate 601 is fixedly arranged on the sampling injection thimble 103.

[0055] Specifically, install the sample sampling tube 1 to be detected at the position to be detected of the automatic thermal desorption desorber, then move the sampling injection thimble 103 towards the conical opening 3. When the sampling injection thimble 103 moves, the outer top rod 1032 applies a thrust force to the guiding plate 601 on the connecting plate 6, causing the guiding plate 601 to drive the elastic telescopic rod 4 to rotate through the connecting plate 6. The elastic telescopic rod 4 drives the positioning block 401 to move, so that the positioning block 401 moves from one end of the arc-shaped groove 2021 to the other end and finally moves outside the arc-shaped groove 2021, thereby releasing the limit on the conical plug 202. As the sampling injection thimble 103 continues to move downward, the top block 1031 on the sampling injection thimble 103 abuts against the conical plug 202, and the conical plug 202 is forced to move downward to squeeze the elastic element 203, causing a gap to appear between the inner wall of the second outer shell 1022 and the first sealing gasket 204. The gas to be detected in the pipe body 101 flows towards the automatic thermal desorption analyzer through the sampling injection thimble 103;

[0056] After the detection is completed, the sampling injection thimble 103 moves upward and no longer abuts against the conical plug 202. The conical plug 202 is reset and moves upward under the push of the elastic element 203, and the first sealing gasket 204 fills the gap between the inner wall of the second outer shell 1022 and the conical plug 202. Even if the elastic force of the elastic element 203 and the torsion spring 5 sleeved outside the elastic telescopic rod 4 weakens, when the elastic force of the elastic element 203 is not enough to push the first sealing gasket 204 to abut against the inner wall of the second outer shell 1022, the arc-shaped groove 2021 will be lower than the height of the positioning block 401. Since the positioning block 401 was originally at one end of the arc-shaped groove 2021 and the arc-shaped groove 2021 is set to be relatively long, even if the elastic force of the torsion spring 5 weakens, the torsion spring 5 can still drive the positioning block 401 on the elastic telescopic rod 4 to reset into the arc-shaped groove 2021. When the elastic telescopic rod 4 resets, the positioning block 401 abuts against the extrusion inclined surface of the top wall of the arc-shaped groove 2021. During the reset of the positioning block 401, it pushes the conical plug 202 to move upward, so that the conical plug 202 moves to the initial position, and the first sealing gasket 204 outside the conical plug 202 abuts against the inner wall of the second outer shell 1022; it should be noted that when the first sealing gasket 204 needs to be replaced due to wear during long-term use, the second outer shell 1022 can be rotated and unscrewed from the first outer shell 1021 to replace the first sealing gasket 204, and the setting of the sealing bearing 402 is beneficial to improving the sealing performance of the connection between the elastic telescopic rod 4 and the sealing head 102.

[0057] Refer to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 6, as a preferred technical solution of the present invention, the auxiliary sealing assembly includes a top plate 7. The top plate 7 is connected to one end of the connecting plate 6 away from the elastic telescopic rod 4. A second sealing gasket 701 is fixedly provided at the bottom of the top plate 7 and is in movable abutment with the top wall of the second outer shell 1022. The conical opening 3 is assisted in sealing by the top plate 7 and the second sealing gasket 701, effectively improving the sealing performance of the sampling tube 1. Moreover, when the sampling needle 103 moves downward, the ejector rod 1032 applies a thrust to the guide plate 601 on the connecting plate 6, so that the guide plate 601 drives the connecting plate 6 to rotate around the elastic telescopic rod 4 as the center, causing the connecting plate 6 to drive the top plate 7 to move and no longer block the conical opening 3, thereby facilitating the bottom of the subsequent sampling needle 103 to enter the conical opening 3 and ensuring the smooth progress of the detection work.

[0058] Refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 6 , as a preferred technical solution of the present invention, the second outer shell 1022 is fixedly provided with a circular ring 8 through a connecting plate. The circular ring 8 is coaxially arranged with the elastic telescopic rod 4. A force-receiving inclined surface is provided at the top of the circular ring 8 and is in movable abutment with the bottom wall of the connecting plate 6. Specifically, when the guide plate 601 is driven by force to drive the connecting plate 6 to rotate around the elastic telescopic rod 4 as the center, the connecting plate 6 abuts against the force-receiving inclined surface at the top of the circular ring 8. As the connecting plate 6 continues to move, the connecting plate 6 is lifted by the force-receiving inclined surface of the circular ring 8, so that the connecting plate 6 drives the top plate 7 to move upward, reducing the friction between the second sealing gasket 701 at the bottom of the top plate 7 and the top wall of the second outer shell 1022 during the movement, thereby ensuring the service life of the second sealing gasket 701.

[0059] Refer to Figure 3 and Figure 6 , as a preferred technical solution of the present invention, abutting inclined surfaces are provided between the pipe body 101 and the first outer shell 1021 and between the first outer shell 1021 and the second outer shell 1022. A third sealing gasket 9 is provided on the abutting inclined surface. Specifically, on the basis of the threaded connection between the pipe body 101 and the first outer shell 1021 and the threaded connection between the first outer shell 1021 and the second outer shell 1022, the cooperation of the third sealing gasket 9 is beneficial to improving the sealing performance of the sealing head 102 itself and the sealing performance between the sealing head 102 and the pipe body 101.

[0060] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A composite thermal desorption air sampling and detection method in the field of occupational health, characterized in that: The following steps are involved: S1: Screening of solid adsorbent materials, screening out multiple solid adsorbents with different specific surface areas that can simultaneously adsorb 24 common vapor-phase organic poisons; S2: Determine the shape and material of the composite thermal desorption air sampling tube (1); S3: processing the solid adsorbent, preparing the screened solid adsorbent material by high temperature, and sequentially filling the prepared solid adsorbents into the sampling tube (1); S4: Sample absorption, using the sampling tube (1) to adsorb 24 common vapor-phase organic poisons in the air; S5: Sample processing, installing the composite thermal desorption air sampling tube (1) on the thermal desorber, heating it, so that the organic vapor is desorbed from the solid adsorbent and carried into the cold hydrazine by the carrier gas flow for pre-concentration. The direction of the carrier gas flow is opposite to that of the sampling, and then it is quickly desorbed at a low flow rate and enters the capillary gas chromatograph through the transmission line.

2. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 1, characterized in that: The multiple solid adsorbents prepared in step S3 are sequentially a first graphitized carbon adsorbent layer, a second graphitized carbon adsorbent layer, a third graphitized carbon adsorbent layer and a carbon molecular sieve adsorbent.

3. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 2, characterized in that: The first graphitized carbon adsorbent layer is 50-120 mg of graphitized carbon adsorbent with a particle size of 20-40 mesh and a specific surface area of ​​20 m2 / g, the second graphitized carbon adsorbent layer is 50-120 mg of graphitized carbon adsorbent with a particle size of 20-40 mesh and a specific surface area of ​​130 m2 / g, the third graphitized carbon adsorbent layer is 50-120 mg of graphitized carbon adsorbent with a particle size of 20-40 mesh and a specific surface area of ​​240 m2 / g, and the carbon molecular sieve adsorbent is 50-120 mg of carbon molecular sieve adsorbent with a particle size of 20-40 mesh and a specific surface area of ​​1200 m2 / g.

4. The composite thermal desorption air sampling and detection method in the field of occupational health according to claim 1, characterized in that: The sampling tube (1) in step S2 comprises a tube body (101) and sealing heads (102) arranged at both ends of the tube body (101), the sealing head (102) comprising a first shell (1021) threadedly connected to the tube body (101) and a second shell (1022) threadedly connected to the first shell (1021), the second shell (1022) having a conical opening (3) at the top, a support plate (2) fixedly provided on the inner wall of the first shell (1021), a guide column (201) fixedly provided on the support plate (2), the guide column (2 01) is slidably connected to the outer side with a conical block (202), an elastic element (203) is arranged between the guide column (201) and the conical block (202), the inner wall of the second shell (1022) is provided with a conical surface matching with the conical block (202), the conical surface is provided with a first sealing gasket (204) movably abutting against the conical block (202), a positioning component for positioning the conical block (202) is arranged on the support plate (2), and an auxiliary sealing component for sealing the conical opening (3) is arranged on the positioning component.

5. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 4, characterized in that: The sampling tube (1) further comprises a sampling ejector pin (103) connected to the detection end of the thermal desorption instrument, wherein the sampling ejector pin (103) is movably connected to the conical opening (3), and a top block (1031) is fixedly disposed at the bottom of the sampling ejector pin (103) and movably abuts against the top of the conical blocking block (202).

6. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 5, characterized in that: The positioning assembly comprises an elastic telescopic rod (4) rotatably connected to a support plate (2); a torsion spring (5) is arranged inside the support plate (2) for driving the elastic telescopic rod (4) to reset and rotate; a positioning block (401) is fixedly arranged on the elastic telescopic rod (4); an arc-shaped groove (2021) matching with the positioning block (401) is provided on the conical blocking block (202); an extrusion inclined surface is provided on the top wall edge of the arc-shaped groove (2021); and a sealed bearing (402) is arranged between the elastic telescopic rod (4) and the second housing (1022).

7. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 6, characterized in that: A connecting plate (6) is fixedly provided at the telescopic end of the elastic telescopic rod (4), a guide plate (601) is fixedly provided on the connecting plate (6), and a push rod (1032) movably abutting against the guide plate (601) is fixedly provided on the injection ejector pin (103).

8. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 7, characterized in that: The auxiliary sealing assembly comprises a top plate (7), the top plate (7) being connected to an end of the connecting plate (6) away from the elastic telescopic rod (4), and a second sealing gasket (701) movably abutting against the top wall of the second outer shell (1022) is fixedly provided at the bottom of the top plate (7).

9. A composite thermal desorption air sampling and detection method in the field of occupational health according to claim 8, characterized in that: The second housing (1022) is fixedly provided with a circular ring (8) via a connecting plate. The circular ring (8) is coaxially arranged with the elastic telescopic rod (4). The top of the circular ring (8) is provided with a force-bearing inclined surface that movably contacts the bottom wall of the connecting plate (6).

10. According to the composite thermal desorption air sampling and detection method in the field of occupational health as described in claim 9, abutment slopes are provided between the tube body (101) and the first shell (1021) and between the first shell (1021) and the second shell (1022), and a third sealing gasket (9) is provided on the abutment slopes.

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