A method for detecting air sampling in the field of occupational health by combined thermal desorption

Abstract

The application discloses a kind of composite thermal desorption air sampling detection methods in occupational health field, belong to thermal desorption technical field.A kind of composite thermal desorption air sampling detection methods in occupational health field, comprising the following steps: S1: the screening of solid adsorbent material, screen multiple solid adsorbent capable of simultaneously adsorbing 24 common vapor state organic toxicants and different specific surface area;S2: determine the shape, material of composite thermal desorption air sampling tube;S3: the processing of solid adsorbent, by high temperature, the solid adsorbent material screened is prepared, and the prepared multiple solid adsorbent is sequentially filled in sampling tube;The application is equipped with a kind of combined solid adsorbent material according to the order of adsorption intensity from small to big using 4 different specific surface area solid adsorbents, can effectively adsorb 24 common vapor state organic toxicants, has higher adsorption capacity, and is not prone to penetration phenomenon.

Description

Technical Field

[0001] This invention relates to the field of thermal desorption technology, and more particularly to a composite thermal desorption air sampling and detection method in the field of occupational health. Background Technology

[0002] Workplace air contains a wide variety of organic toxins, varying in toxicity and concentration. Common organic toxins exist primarily in vapor form at room temperature in workplace air, such as alkanes, alkenes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, esters, and nitriles. These common organic toxins are widely present in environmental media such as air, water, and soil. They are highly toxic and can be absorbed through the respiratory tract, digestive tract, and skin. Most organic toxins have irritating effects on human skin, conjunctiva, and respiratory organs; some are also carcinogenic. With a large number of people exposed to them, they pose significant occupational health risks.

[0003] Currently, the standard method in my country's occupational health field mainly adopts solvent desorption-gas chromatography to detect common vaporized organic toxins in workplace air. It mainly uses activated carbon tubes and silica gel tubes for collection. The collected samples need to be processed with different desorption solutions, which is not conducive to practical work. Moreover, the desorption solution mainly uses highly toxic carbon disulfide, which is very harmful to laboratory personnel and the ecological environment.

[0004] Chinese patent application number CN202211521625.3 discloses a novel sample sampling tube, including a sample tube and an automatic thermal desorption / desorption apparatus. It further includes: a sealing head, located at both ends of the sample tube and sealed to it; an injection pin, connected to the detection end of the automatic thermal desorption / desorption apparatus; and a sealing structure located inside the sealing head for sealing the sealing head and cooperating with the injection pin, facilitating assembly, use, and replacement of the sealing gasket. However, in actual operation, the sealing structure relies solely on the stabilizing spring force to push the sealing gasket against the fixed column to isolate the sealing head from the outside environment. When the stabilizing spring force weakens, the sealing effect of the sealing head deteriorates, affecting the thermal desorption detection effect. Furthermore, when the fixed column slides relative to the sealing gasket, the sealing gasket is easily worn, requiring the removal and replacement of the limiting sleeve, making the operation cumbersome. Summary of the Invention

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

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

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

[0008] S1: Screening of solid adsorbent materials, identifying several solid adsorbents with different specific surface areas that can simultaneously adsorb 24 common vapor organic toxins.

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

[0010] S3: Solid adsorbent processing: The screened solid adsorbent materials are prepared by high temperature, and multiple prepared solid adsorbents are sequentially filled into the sampling tube;

[0011] S4: Sample absorption, using a sampling tube to adsorb 24 common vaporized organic toxins in the air;

[0012] S5: Sample processing. The composite thermal desorption air sampling tube is installed on the thermal desorber and heated to desorb the organic vapor from the solid adsorbent. The vapor is then carried by the carrier gas flow into the cold hydrazine for pre-concentration. The direction of the carrier gas flow is opposite to that during sampling. Then, the vapor is rapidly desorbed at a low flow rate and enters the capillary gas chromatograph via a transfer line.

[0013] Preferably, the plurality of solid adsorbents prepared in step S3 are, in sequence, 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 composed of 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 composed of 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 composed of 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 composed of 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.

[0015] Preferably, the sampling tube in step S2 includes a tube body and sealing heads disposed 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. The top of the second outer shell has a tapered opening. A support plate is fixedly disposed on the inner wall of the first outer shell. A guide post is fixedly disposed on the support plate. A tapered plug is slidably connected to the outer side of the guide post. An elastic element is disposed between the guide post and the tapered plug. The inner wall of the second outer shell has a tapered surface that mates with the tapered plug. A first sealing gasket is disposed on the tapered surface that moves against the tapered plug. A positioning component for positioning the tapered plug is disposed on the support plate. An auxiliary sealing component for sealing the tapered opening is disposed on the positioning component.

[0016] Preferably, the sampling tube further includes an injection pin connected to the detection end of the thermal desorption instrument. The injection pin is movably connected to the conical opening, and a top block is fixed at the bottom of the injection pin to movably abut against the top of the conical block.

[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 return to its original rotation is provided inside the support plate, a positioning block is fixed on the elastic telescopic rod, an arc-shaped groove that cooperates with the positioning block is provided on the conical block, an extrusion slope is provided on the top edge of the arc-shaped groove, and a sealed bearing is provided 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 guide plate is fixedly provided on the connecting plate, and a push rod is fixedly provided on the injection pin to move against the guide plate.

[0019] Preferably, the auxiliary sealing assembly includes a top plate, which is connected to the end of the connecting plate away from the elastic telescopic rod, and a second sealing gasket is fixedly provided at the bottom of the top plate to move against the top wall of the second housing.

[0020] Preferably, the second outer shell is fixed with a ring via a connecting plate. The ring is coaxially arranged with the elastic telescopic rod, and the top of the ring has a force-bearing inclined surface that moves against the bottom wall of the connecting plate.

[0021] Preferably, abutting slopes are provided between the tube body and the first outer shell, and between the first outer shell and the second outer shell, and a third sealing gasket is provided on the abutting slopes.

[0022] Compared with existing technologies, this invention provides a composite thermal desorption air sampling and detection method in the field of occupational health, which has the following beneficial effects:

[0023] 1. This occupational health field composite thermal desorption air sampling and detection method uses four solid adsorbents with different specific surface areas, assembled in order of increasing adsorption strength to form a composite solid adsorbent material. It can effectively adsorb 24 common vapor organic toxins, has a high adsorption capacity, and is not prone to penetration.

[0024] 2. The composite thermal desorption air sampling and detection method in the field of occupational health uses an elastic telescopic rod to reset, which causes the positioning block to abut against the squeezing inclined surface of the top wall of the arc-shaped groove. During the reset of the positioning block, the conical plug is pushed upward, so that the conical plug moves to the initial position. The first sealing gasket on the outside of the conical plug abuts against the inner wall of the second shell. Even if the elastic force of the elastic element weakens, the sealing between the conical plug and the second shell can still be guaranteed, avoiding the leakage of sample gas in the sampling tube.

[0025] 3. This occupational health field composite thermal desorption air sampling and detection method uses a top plate and a second sealing gasket to provide auxiliary sealing for the conical opening, effectively improving the sealing performance of the sampling tube. Furthermore, the downward movement of the injection pin causes the push rod to exert 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 as the center. At the same time as the positioning block releases the restriction on the conical block, the connecting plate drives the top plate to move and no longer blocks the conical opening, thus facilitating the entry of the bottom of the injection pin into the conical opening and ensuring the smooth progress of the detection work.

[0026] 4. In this occupational health field, the composite thermal desorption air sampling and detection method involves a guide plate being forced to rotate a connecting plate around an elastic telescopic rod. When the connecting plate rotates, it comes into contact with the inclined surface of the top of the ring. As the connecting plate continues to move, it is lifted by the inclined surface of the ring, which in turn causes the top plate to move upward. This reduces the friction between the second sealing gasket at the bottom of the top plate and the top wall of the second outer shell during the movement, thus ensuring the service life of the second sealing gasket. Attached Figure Description

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

[0028] Figure 2 For the present invention Figure 1 A partially enlarged structural diagram of section A in the middle;

[0029] Figure 3 This is a cross-sectional structural diagram of the sealing head of the present invention;

[0030] Figure 4 For the present invention Figure 3 A partially enlarged structural diagram of section B in the middle;

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

[0032] Figure 6 This is a schematic diagram of the structure of the sample injection pin of the present invention when it abuts against the conical plug;

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

[0034] In the diagram: 1. Sampling tube; 101. Tube body; 102. Sealing head; 1021. First outer shell; 1022. Second outer shell; 103. Injection pin; 1031. Top block; 1032. Top rod; 2. Support plate; 201. Guide column; 202. Conical plug; 2021. Arc groove; 203. Elastic element; 204. First sealing gasket; 3. Conical opening; 4. Elastic telescopic rod; 401. Positioning block; 402. Sealed 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

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" 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 a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Example: Refer to Figure 1-7 A method for sampling and detecting air using composite thermal desorption in the field of occupational health includes the following steps:

[0039] S1: Screening of solid adsorbent materials, identifying several solid adsorbents with different specific surface areas that can simultaneously adsorb 24 common vapor organic toxins.

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

[0041] S3: Solid adsorbent processing: The screened solid adsorbent materials are prepared by high temperature, and multiple prepared solid adsorbents are sequentially filled into sampling tube 1;

[0042] S4: Sample absorption, using sampling tube 1 to adsorb 24 common vaporized organic toxins in the air;

[0043] S5: Sample processing. The composite thermal desorption air sampling tube 1 is installed on the thermal desorber and heated to desorb the organic vapor from the solid adsorbent. The vapor is then carried by the carrier gas flow into the cold hydrazine for pre-concentration. The direction of the carrier gas flow is opposite to that during sampling. The vapor is then rapidly desorbed at a low flow rate and enters the capillary gas chromatograph via a transfer line.

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

[0045] Furthermore, the first graphitized carbon adsorbent layer is composed of 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 composed of 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 composed of 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 composed of 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.

[0046] Specifically, sampling tube 1 is a cylindrical tube with standard dimensions: length 90mm, outer diameter 6.3mm, and inner diameter 5mm. Sampling tube 1 can be made of stainless steel or hard glass. The filling method for the solid adsorbent in the composite thermal desorption air sampling tube is as follows: First, place stainless steel wire or silanized glass wool with pore sizes smaller than the solid adsorbent particle size at the bottom of sampling tube 1 (i.e., the sampling outlet end) (to prevent the solid adsorbent from falling off). Then, sequentially add 50-120mg of carbon molecular sieve adsorbent with a particle size of 20-40 mesh and a specific surface area of ​​1200m² / g, 50-120mg of third-generation graphitized carbon adsorbent with a particle size of 20-40 mesh and a specific surface area of ​​240m² / g, and 50- 120 mg of a 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 a 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 stainless steel wire or silanized glass wool with pores smaller than the particle size of the solid adsorbent is placed in it (to prevent the solid adsorbent from falling out); finally, seals are fitted to both ends of sampling tube 1. It should be noted that the position of the solid adsorbent filled in sampling tube 1 should be at least 15 mm away from the sampling inlet end of sampling tube 1, and the length of the solid adsorbent should not exceed the size of the heating zone of the thermal desorption instrument; sampling tube 1 should have a sampling airflow direction indicator; the filled sampling tube 1 should be tested for resistance, and at a flow rate of 0.05 L / min for a long time of 480 min, the airflow resistance should be less than 4.0 kPa.

[0047] Furthermore, by graphitizing activated carbon with specific pore sizes at high temperatures (above 3000℃) to form graphitized carbon adsorbents with different specific surface areas and extremely low background, and by activating molecular sieves with specific pore sizes through a template and then carbonizing them at high temperatures (above 1000℃) to form carbon molecular sieve adsorbents with extremely low background, it is ensured that the different solid adsorbents prepared do not contain the above 24 common vapor organic toxins or substances that can interfere with the determination of the above 24 common vapor organic toxins.

[0048] In addition, during sample processing, the composite thermal desorption air sampling tube 1 is installed on the thermal desorber and heated to desorb organic vapors from the solid adsorbent. The vapors are then carried by the carrier gas flow into the cold hydrazine for pre-concentration. The direction of the carrier gas flow is opposite to that during sampling. The vapors are then rapidly desorbed at a low flow rate and enter the capillary gas chromatograph via a transfer line.

[0049] The sample determination conditions are as follows: Thermal desorption / desorption conditions: Sample tube desorption temperature: 300℃; Desorption time: 10 min; Dry purge: 1 min; Transfer line temperature: 210℃; Valve temperature: 200℃; Trap temperature: Low temperature -30℃, High temperature 300℃, Heating rate 40℃ / s; Trap desorption time: 7 min; Outlet split: 14 ml / min; Inlet split: 60 ml / min; Desorption flow rate: 50 mL / min. Chromatographic determination conditions: Detector: Flame ionization detector (FID); Column: 60 m × 0.25 mm × 1.00 μm, DB-5MS; Detector temperature: 300℃; Carrier gas (nitrogen) flow rate: Constant flow rate 1.0 mL / min; Column temperature: Initial temperature 40℃, hold for 10.00 min, increase to 250℃ at 5℃ / min, hold for 4.00 min.

[0050] This technology assembles a composite thermal desorption air sampling tube 1 by loading 4 kinds of solid adsorbents (filled in a mass ratio of 1:1, and the specific surface area of the solid adsorbents filled from the sampling inlet end to the sampling outlet end increases from small to large), which can effectively collect 24 common vaporous organic poisons in workplace air, such as acetonitrile, acrylonitrile, acetone, butanone, cyclohexanone, benzene, toluene, xylene (all isomers), methyl acetate, ethyl acetate, butyl acetate, vinyl acetate, styrene, ethylene glycol monobutyl ether, n-hexane, dichloromethane, 1,2-dichloroethane, chloroform, trichloroethylene, isopropanol, n-butanol, carbon disulfide, etc. When the mass concentration of the above 24 common vaporous organic poisons in workplace air is 1 - 500 mg / m3, the developed air sampling tube 1 is used to collect for 15 min at 0.20 L / min, and the short-time sampling efficiency of each target component is 100.0%; when the mass concentration of the above 24 common vaporous organic poisons in workplace air is 1 - 500 mg / m3, the developed air sampling tube 1 is used to collect for 480 min at 0.05 L / min, and the long-time sampling efficiency of each target component is greater than 90%, and no breakthrough phenomenon will occur. The total adsorption capacity of the above 24 common vaporous organic poisons is greater than 5 mg. When the mixed standard series gas of the above 24 common vaporous organic poisons is measured by this method and the content is 0 - 500 μg, the correlation coefficient is 0.9992 - 0.9999, the detection limit is 0.003 - 0.06 μg (calculated by 3 times the standard deviation), the lower limit of quantification is 0.005 - 0.010 μg (calculated by 10 times the standard deviation), the lowest detection concentration in air is 0.001 - 0.002 mg / m3 (both calculated based on collecting 3.0 L of samples), and the lowest quantification concentration is 0.002 - 0.004 mg / m3 (both calculated based on collecting 3.0 L of samples); the average thermal desorption efficiency is greater than 95%, the accuracy meets the technical requirements between 95% - 105%, and the precision relative standard deviation is less than 10%; the air sampling tube 1 that has collected the above 24 common vaporous organic poisons in workplace air can be stably stored for more than 7 days at 4°C under sealed storage conditions; the possible coexisting interfering substances in the on-site workplace air (such as methyl methacrylate, methyl isobutyl ketone, isophorone, etc.) do not affect the determination. Therefore, the determination method配套 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 vaporous organic poisons in workplace air. All in all, this technology can achieve simultaneous collection and detection of the above 24 common vaporous organic poisons in workplace air, greatly improving the accuracy and sensitivity of the method, and can perform simultaneous sampling and simultaneous detection in any sampling method (personal sampling or fixed-point sampling, long-time sampling or short-time sampling), overcoming the drawbacks of the current need to use different air sampling tubes for collection, different desorption solutions for sample pretreatment, and different detection methods for determination, and greatly enhancing 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 aforementioned 24 common vaporized organic toxins in workplace air, but also to collect other common vaporized organic toxins in workplace air. By optimizing the sample thermal desorption conditions and instrument detection conditions, a series of supporting qualitative and quantitative determination methods are formed. It is expected that this will enable rapid, efficient, and comprehensive monitoring of the concentration levels of more common vaporized organic toxins in workplace air, and will also provide strong technical support for the effective handling of sudden chemical poisoning incidents caused by common vaporized organic toxins. Therefore, the development of the composite thermal desorption air sampling tube 1 and its supporting determination methods have broad application prospects.

[0051] Reference 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 disposed 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 disposed on the inner wall of the first outer shell 1021. A guide post 201 is fixedly disposed on the support plate 2. A conical block 202 is slidably connected to the outer side of the guide post 201. An elastic element 203 is disposed between the guide post 201 and the conical block 202. A conical surface that cooperates with the conical block 202 is provided on the inner wall of the second outer shell 1022. A first sealing gasket 204 that moves against the conical block 202 is disposed on the conical surface. A positioning component for positioning the conical block 202 is disposed on the support plate 2. An auxiliary sealing component for sealing the conical opening 3 is disposed on the positioning component.

[0052] Furthermore, the sampling tube 1 also includes a sample injection pin 103 connected to the detection end of the thermal desorption instrument. The sample injection pin 103 is movably connected to the conical opening 3, and a top block 1031 is fixed at the bottom of the sample injection pin 103 to movably abut against the top of the conical block 202.

[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 return to its original rotation is provided inside the support plate 2, a positioning block 401 is fixed on the elastic telescopic rod 4, an arc-shaped groove 2021 that cooperates with the positioning block 401 is provided on the conical block 202, an extrusion slope is provided on the top edge of the arc-shaped groove 2021, and a sealed bearing 402 is provided between the elastic telescopic rod 4 and the second outer shell 1022.

[0054] Furthermore, 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 that moves against the guide plate 601 is fixedly provided on the injection pin 103.

[0055] Specifically, the sample tube 1 to be tested is installed at the test position of the automatic thermal desorption / desorption instrument. Then, the injection pin 103 moves in alignment with the conical opening 3. When the injection pin 103 moves, the outer push rod 1032 applies a pushing force to the guide plate 601 on the connecting plate 6, causing the guide 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, causing the positioning block 401 to move from one end of the arc groove 2021 to the other end. And finally move to the outside of the arc groove 2021, thereby releasing the restriction on the conical block 202. As the injection pin 103 continues to move down, the top block 1031 on the injection pin 103 abuts against the conical block 202. The conical block 202 is forced to move down and squeeze the elastic element 203, so that a gap appears between the inner wall of the second outer shell 1022 and the first sealing gasket 204. The gas to be detected in the tube 101 flows to the automatic thermal desorption analyzer through the injection pin 103.

[0056] After the test is completed, the injection pin 103 moves upward and no longer abuts against the conical plug 202. The conical plug 202 is reset and moved 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 on the outside of the elastic telescopic rod 4 weakens, when the elastic force of the elastic element 203 is insufficient to push the first sealing gasket 204 to abut against the inner wall of the second outer shell 1022, the arc 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 groove 2021 and the arc groove 2021 is relatively long, even if the elastic force of the torsion spring 5 weakens, the torsion spring 5 can still drive the elastic telescopic rod. The positioning block 401 on the elastic telescopic rod 4 is reset to the arc groove 2021. When the elastic telescopic rod 4 is reset, it drives the positioning block 401 to abut against the pressing slope of the top wall of the arc groove 2021. During the reset, the positioning block 401 pushes the conical block 202 upward, so that the conical block 202 moves to the initial position. The first sealing gasket 204 on the outside of the conical block 202 abuts against the inner wall of the second outer shell 1022. It should be noted that when the first sealing gasket 204 is worn and needs to be replaced during long-term use, the first sealing gasket 204 can be replaced by rotating and unscrewing the second outer shell 1022 from the first outer shell 1021. 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] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 6As a preferred technical solution of the present invention, the auxiliary sealing assembly includes a top plate 7, which is connected to the 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 moves against the top wall of the second outer shell 1022. The top plate 7 and the second sealing gasket 701 provide auxiliary sealing for the conical opening 3, which effectively improves the sealing performance of the sampling tube 1. The downward movement of the injection pin 103 causes the push rod 1032 to apply a pushing force to the guide plate 601 on the connecting plate 6, thereby causing the guide plate 601 to drive the connecting plate 6 to rotate around the elastic telescopic rod 4. This causes the connecting plate 6 to move the top plate 7 and no longer block the conical opening 3, thus facilitating the entry of the bottom of the injection pin 103 into the conical opening 3 and ensuring the smooth progress of the detection work.

[0058] Reference 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 ring 8 by a connecting plate. The ring 8 is coaxially arranged with the elastic telescopic rod 4. The top of the ring 8 is provided with a force-bearing inclined surface that moves against the bottom wall of the connecting plate 6. Specifically, when the guide plate 601 is subjected to force and drives the connecting plate 6 to rotate around the elastic telescopic rod 4, the connecting plate 6 abuts against the force-bearing inclined surface at the top of the ring 8. As the connecting plate 6 continues to move, the connecting plate 6 is lifted by the force-bearing inclined surface of the ring 8, thereby causing the connecting plate 6 to drive the top plate 7 to move upward. This reduces 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] Reference Figure 3 and Figure 6 As a preferred technical solution of the present invention, abutting slopes are provided between the tube body 101 and the first outer shell 1021 and between the first outer shell 1021 and the second outer shell 1022, and a third sealing gasket 9 is provided on the abutting slopes; specifically, the tube body 101 and the first outer shell 1021 are connected by threads, and the first outer shell 1021 and the second outer shell 1022 are connected by threads, and with the cooperation of the third sealing gasket 9, it is beneficial to improve the sealing performance of the sealing head 102 itself and the sealing performance between the sealing head 102 and the tube body 101.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for sampling and detecting air using composite thermal desorption in the field of occupational health, characterized in that, Includes the following steps: S1: Screening of solid adsorbent materials, identifying several solid adsorbents with different specific surface areas that can simultaneously adsorb 24 common vapor organic toxins. S2: Determine the shape and material of the composite thermal desorption air sampling tube (1); S3: Solid adsorbent processing: The selected solid adsorbent materials are prepared by high temperature, and the prepared solid adsorbents are sequentially filled into the sampling tube (1). S4: Sample absorption, using sampling tube (1) to adsorb 24 common vapor organic toxins in the air; S5: Sample processing: Install the composite thermal desorption air sampling tube (1) on the thermal desorption instrument, heat 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 the direction of sampling. Then, it is rapidly desorbed at a low flow rate and enters the capillary gas chromatograph through the transfer line. The sampling tube (1) in step S2 includes a tube body (101) and sealing heads (102) disposed 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). The top of the second outer shell (1022) is provided with a tapered opening (3). 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). 01) A conical plug (202) is slidably connected to the outside. An elastic element (203) is provided between the guide post (201) and the conical plug (202). The inner wall of the second outer shell (1022) is provided with a conical surface that cooperates with the conical plug (202). A first sealing gasket (204) is provided on the conical surface that moves against the conical plug (202). A positioning component for positioning the conical plug (202) is provided on the support plate (2). An auxiliary sealing component for sealing the conical opening (3) is provided on the positioning component. The sampling tube (1) also includes an injection pin (103) connected to the detection end of the thermal desorption instrument. The injection pin (103) is movably connected to the conical opening (3). The bottom of the injection pin (103) is fixed with a top block (1031) that movably abuts against the top of the conical block (202). 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 in the support plate (2), a positioning block (401) is fixed on the elastic telescopic rod (4), an arc groove (2021) that cooperates with the positioning block (401) is provided on the conical block (202), an extrusion slope is provided on the top wall edge of the arc groove (2021), and a sealed bearing (402) is provided between the elastic telescopic rod (4) and the second outer shell (1022); The telescopic end of the elastic telescopic rod (4) is fixedly provided with a connecting plate (6), a guide plate (601) is fixedly provided on the connecting plate (6), and a push rod (1032) is fixedly provided on the injection pin (103) to move against the guide plate (601).

2. The method for combined thermal desorption air sampling and detection in the field of occupational health according to claim 1, characterized in that, The multiple solid adsorbents prepared in step S3 are, in sequence, 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. The method for combined thermal desorption air sampling and detection in the field of occupational health according to claim 2, characterized in that, The first graphitized carbon adsorbent layer consists of 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 consists of 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 consists of 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 consists of 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 method for combined thermal desorption air sampling and detection in the field of occupational health according to claim 1, characterized in that, The auxiliary sealing assembly includes a top plate (7), which is connected to the 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 moves against the top wall of the second outer shell (1022).

5. The method for combined thermal desorption air sampling and detection in the field of occupational health according to claim 4, characterized in that, The second outer shell (1022) is fixed with a ring (8) by a connecting plate. The ring (8) is coaxially arranged with the elastic telescopic rod (4). The top of the ring (8) is provided with a force-bearing inclined surface that moves against the bottom wall of the connecting plate (6).

6. According to claim 5, a composite thermal desorption air sampling and detection method in the field of occupational health is provided with abutting slopes between the tube body (101) and the first outer shell (1021) and between the first outer shell (1021) and the second outer shell (1022), and a third sealing gasket (9) is provided on the abutting slope.

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