Compound thermal desorption air sampling tube for occupational health field

Abstract

The utility model provides a kind of composite thermal desorption air sampling tube in occupational health field, belong to occupational health technical field, including pipe body, the inside of pipe body is equipped with multiple solid adsorbents from inlet end to outlet end in turn, the multiple solid adsorbents include first graphitized carbon adsorbent layer, second graphitized carbon adsorbent layer, third graphitized carbon adsorbent layer and carbon molecular sieve adsorbent;And sealing cap, the sealing cap is sealed and is arranged in the both ends of pipe body, the sealing cap includes the sealing portion being connected with pipe body and the connecting portion being integrally formed with sealing portion;The utility model is assembled into a kind of combined solid adsorbent material according to the order of adsorption strength from small to big with 4 different specific surface area solid adsorbents, can effectively adsorb 24 kinds of common vapour state organic toxicants, with higher adsorption capacity, not easy to occur penetration phenomenon.

Description

Technical Field

[0001] This utility model relates to the field of occupational health technology, specifically to a composite thermal desorption air sampling tube for 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 are irritating to human skin, conjunctiva, and respiratory organs; some are also carcinogenic. Occupational exposure to these toxins affects a large number of people, posing significant occupational health risks.

[0003] Currently, the standard method in my country's occupational health field mainly uses solvent desorption-gas chromatography to detect common vaporized organic toxins in workplace air. This method primarily uses activated carbon and silica gel tubes for sample collection, and the collected samples require processing with different desorption solutions, which is inconvenient for practical work. Furthermore, the use of highly toxic carbon disulfide as the desorption solution poses significant risks to laboratory personnel and the environment. Thermal desorption-chromatography / mass spectrometry, on the other hand, eliminates the need for organic solvents, aligning with the requirements of green and low-carbon high-quality development. Its sensitivity is also far superior to solvent desorption methods, making it widely used in the detection of volatile organic compounds in ambient and indoor air. However, there is currently no suitable thermal desorption tube for occupational health, hindering the widespread application of thermal desorption technology in this field.

[0004] On the one hand, in the field of occupational health, the current national occupational health standard detection method mainly adopts the solid adsorbent tube collection solvent desorption-gas chromatography method to detect organic toxins. There are many types of desorption solvents, and carbon disulfide is widely used due to its good physicochemical properties. However, the following problems still exist: ① The current detection method usually involves adding 1.0 mL of carbon disulfide to desorb the solid adsorbent, and then taking 1.0 μL of the sample solution for gas chromatography detection. This method has low sensitivity and consumes a large amount of organic solvent, resulting in unnecessary waste. ② Desorption solvents such as carbon disulfide, which are highly volatile and toxic, can be inhaled through the respiratory tract, skin, and digestive tract, posing a certain degree of harm to the physical and mental health of laboratory personnel. Furthermore, desorption solvents are discharged into the living environment through the atmosphere or water, causing serious impacts on the local ecological environment. Therefore, the occupational health field urgently needs a green, safe, and environmentally friendly detection method to replace the solvent desorption method that uses large amounts of organic solvents. Thermal desorption eliminates the need for organic solvents, reducing the risk of exposure to toxic chemicals for laboratory personnel. Its sensitivity is far superior to solvent desorption methods, making it a green, safe, and environmentally friendly method, as well as accurate, sensitive, and fully automated. It is widely used for detecting volatile organic compounds (VOCs) in ambient and indoor air. However, thermal desorption is not widely applied in occupational health. This is because it primarily uses poly(2,6-diphenyl-p-phenylene ether) (Tenax) tubes to collect organic pollutants. While Tenax tubes offer good thermal desorption, they have weak adsorption capacity for low-boiling-point organic pollutants and are prone to penetration. Furthermore, workplaces in different types of enterprises in the occupational health field contain various organic pollutants with wide concentration ranges, making conventional thermal desorption tubes unsuitable. Therefore, there is an urgent need to develop a thermal desorption tube suitable for occupational health and establish a corresponding thermal desorption detection method to fill the current gap in the application of thermal desorption technology in occupational health and better promote the high-quality development of occupational health.

[0005] On the other hand, in the field of occupational health, most of the existing national occupational health standard testing methods can only collect and detect one or a certain type of organic toxicant, exhibiting a certain degree of specialization. However, workplace air often contains multiple types of organic toxicants, and the lack of universal standard testing methods leads to a significant waste of human and material resources and affects the accuracy of sampling and testing results. Firstly, large-scale sampling of various common organic toxicants on-site requires different sampling media; laboratories need to use different analytical methods to detect certain types of organic toxicants, causing analytical instruments to operate under overload, sample accumulation exceeding the testing time limit, and high costs for both on-site sampling and laboratory testing. Secondly, according to current sampling specifications, most organic toxicants have established long-term weighted average tolerance concentrations (PC-TWA), requiring priority to be given to individual sampling methods. Workers need to wear multiple sampling devices to collect samples of different common organic toxicants, affecting their normal work. Worker compliance during on-site sampling is low, which may lead to difficulties in detecting the true concentration levels of common organic toxicants. Therefore, in order to better meet various testing needs, it is urgent to develop universal standard testing methods to achieve the goal of simultaneously collecting and detecting multiple common organic toxins in workplace air. Utility Model Content

[0006] This invention provides a composite thermal desorption air sampling tube for occupational health. The composite thermal desorption air sampling tube is assembled by filling it with four kinds of solid adsorbents and can simultaneously and effectively collect 24 common vaporized organic toxins in workplace air.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A composite thermal desorption air sampling tube for occupational health applications, comprising:

[0009] The tube body, with multiple layers of solid adsorbent sequentially arranged from the inlet to the outlet, includes a first graphitized carbon adsorbent layer, a second graphitized carbon adsorbent layer, a third graphitized carbon adsorbent layer, and a carbon molecular sieve adsorbent; and

[0010] A sealing cap is provided at both ends of the pipe body. The sealing cap includes a sealing part connected to the pipe body and a connecting part integrally formed with the sealing part.

[0011] Preferably, the two ends of the tube are further provided with a protective layer, the pores of which are smaller than the particle size of the solid adsorbent, and the protective layer is stainless steel wire or silanized glass wool.

[0012] Preferably, the first graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​20 μm, with a particle size of 50-120 mg. 2 / g of graphitized carbon adsorbent.

[0013] Preferably, the second graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​50-120 mg. 2 / g of graphitized carbon adsorbent.

[0014] Preferably, the third graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​240 μm, with a particle size of 50-120 mg. 2 / g of graphitized carbon adsorbent.

[0015] Preferably, the carbon molecular sieve adsorbent has a particle size of 20-40 mesh and a specific surface area of ​​1200 μm, with a particle size of 50-120 mg. 2 / g of carbon molecular sieve adsorbent.

[0016] Preferably, the sealing part includes a sealing cover, an elastic locking block that slides along the inner wall of the sealing cover, and a sealing ring disposed on the bottom wall of the inner cavity of the sealing cover and capable of engaging with the end of the tube.

[0017] Preferably, the two end sidewalls of the tube body are provided with annular grooves, the annular grooves include an inner bottom wall and an inclined groove that gradually expands from the inner bottom wall to the outer wall of the tube body, and the end of the tube body is provided with a guide groove communicating with the annular groove along its axial direction.

[0018] Preferably, the size of the elastic block is adapted to the guide groove.

[0019] Preferably, the connecting part is a mating cover disposed at the top of the sealing part.

[0020] As can be seen from the above technical solutions, this utility model has the following beneficial effects:

[0021] 1. In this invention, a composite thermal desorption air sampling tube is assembled from solid adsorbents of different specific surface areas in a specific order to collect common vaporous organic pollutants in workplace air, such as alkanes, alkenes, aromatics, halogenated hydrocarbons, alcohols, ethers, ketones, esters, and nitriles. Since solid adsorbents of different specific surface areas do not have the same adsorption effect on different types of organic pollutants, and some even show significant differences in adsorption effect, this study selected 24 common vaporous organic pollutants for systematic experimental research. Extensive experiments showed that assembling four solid adsorbents of different specific surface areas in order of increasing adsorption strength (from the sampling inlet to the sampling outlet) into a composite solid adsorbent material (with a 1:1 mass ratio of different solid adsorbents) can effectively adsorb 24 common vaporous organic pollutants, possessing a high adsorption capacity and being less prone to penetration. Attached Figure Description

[0022] Figure 1 This is a perspective view of the present invention;

[0023] Figure 2 This is a partial cross-sectional view of the present invention;

[0024] Figure 3 for Figure 2 A magnified view of part A in the middle;

[0025] Figure 4 for Figure 2 A magnified view of part B in the middle section.

[0026] In the figure: 10, pipe body; 110, annular groove; 111, inner bottom wall; 112, inclined groove; 120, guide groove; 20, sealing cap; 211, sealing cover; 212, elastic block; 213, limiting groove; 214, spring; 221, docking cover. Detailed Implementation

[0027] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] To achieve the above objectives, the embodiments of this utility model adopt the following technical solutions: (Refer to...) Figure 1 A composite thermal desorption air sampling tube for occupational health includes a tube body 10 and a sealing cap 20. Further, the tube body 10 has multiple solid adsorbents arranged sequentially from the inlet end to the outlet end. The multiple solid adsorbents include a first graphitized carbon adsorbent layer, a second graphitized carbon adsorbent layer, a third graphitized carbon adsorbent layer, and a carbon molecular sieve adsorbent. There are two sealing caps 20, and the two sealing caps 20 are sealed at both ends of the tube body 10. The sealing cap includes a sealing part connected to the tube body 10 and a connecting part integrally formed with the sealing part.

[0029] Furthermore, the two ends of the tube 10 are provided with a protective layer. The pores of the protective layer are smaller than the particle size of the solid adsorbent. The protective layer is made of stainless steel wire or silanized glass wool.

[0030] Furthermore, the first graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​20 m², with a particle size of 50-120 mg. 2 / g of graphitized carbon adsorbent;

[0031] The second graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​50-120 mg. 2 / g of graphitized carbon adsorbent;

[0032] The third graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​50-120 mg. 2 / g of graphitized carbon adsorbent;

[0033] The carbon molecular sieve adsorbent has a particle size of 20-40 mesh and a specific surface area of ​​1200 m³, with a particle size of 50-120 mg. 2 / g of carbon molecular sieve adsorbent

[0034] The tube body 10 is a cylindrical tube with standard dimensions: 90mm in length and 6.3mm in outer diameter (5mm in inner diameter). The tube body 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 the tube body (i.e., the sampling outlet end) (to prevent the solid adsorbent from falling off). Then, sequentially add 50-120mg of material with a particle size of 20-40 mesh and a specific surface area of ​​1200µm. 2 / g of carbon molecular sieve adsorbent, 50-120mg particle size, 20-40 mesh, specific surface area 240m 2 / g of the third graphitized carbon adsorbent, 50-120mg particle size, 20-40 mesh, specific surface area 130m 2 / g of the second graphitized carbon adsorbent, 50-120mg particle size, 20-40 mesh, specific surface area 20m 2 The first layer of graphitized carbon adsorbent is used (various solid adsorbents are separated by inert materials such as silanized glass wool, carbon wool, or quartz wool), followed by 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 out); finally, sealing caps are placed on both ends of the sampling tube. It should be noted that the position of the solid adsorbent filled in the sampling tube should be at least 15 mm away from the sampling inlet end of the sampling tube, and the length of the solid adsorbent should not exceed the size of the heating zone of the thermal desorption instrument; the sampling tube should have a sampling airflow direction indicator; the filled sampling tube 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.

[0035] Furthermore, by graphitizing activated carbon with specific pore sizes at high temperatures (above 3000℃) to form graphitized carbon adsorbents with extremely low background and different specific surface areas, 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 vaporized organic toxins or substances that can interfere with the determination of the above 24 common vaporized organic toxins.

[0036] In addition, during sample processing, the composite thermal desorption air sampling tube is installed on the thermal desorber and heated to desorb organic vapors from the solid adsorbent. These vapors are then carried by a carrier gas flow into a cold hydrazine atmosphere 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 fed into a capillary gas chromatograph via a transfer line.

[0037] 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 mm m, 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.

[0038] This technology utilizes a composite thermal desorption air sampling tube assembled with four types of solid adsorbents (filled in a 1:1 mass ratio, with the specific surface area of ​​the solid adsorbents increasing from the sampling inlet to the sampling outlet). This tube can simultaneously and effectively collect 24 common vaporized organic pollutants from workplace air, 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, chloroform, trichloroethylene, isopropanol, n-butanol, and carbon disulfide. When the mass concentration of these 24 common vaporized organic pollutants in workplace air is between 1 and 500 mg / m³... 3 When the developed air sampling tube was used to collect samples at a rate of 0.20 L / min for 15 min, the short-time sampling efficiency for each target component was 100.0%; when the mass concentration of the above 24 common vaporous organic toxins in the workplace air was between 1 and 500 mg / m³ 3During the sampling process, the developed air sampling tube was used to collect samples at a rate of 0.05 L / min for 480 min. The long-term sampling efficiency of each target component was greater than 90%, and no penetration phenomenon occurred. The total adsorption capacity of the above 24 common vaporized organic toxins was greater than 5 mg. The method determined that the correlation coefficient of the above 24 common vaporized organic toxin mixed standard gas series gases with a concentration of 0–500 μg was 0.9992–0.9999, the detection limit was 0.003–0.06 μg (calculated at 3 standard deviations), the quantitation limit was 0.005–0.010 μg (calculated at 10 standard deviations), and the lowest detectable concentration in air was 0.001–0.002 mg / m³. 3 (Based on 3.0 L sample volume), the minimum quantitation concentration is 0.002–0.004 mg / m³. 3 (All measurements were based on 3.0 L samples); the average thermal desorption efficiency was greater than 95%, the accuracy met the technical requirements of 95%–105%, and the relative standard deviation of precision was less than 10%; the air sampling tubes that collected samples of the above 24 common vaporized organic toxins in workplace air could be stably stored for more than 7 days at 4°C under sealed storage conditions; interfering substances that may coexist in workplace air (such as methyl methacrylate, methyl isobutyl ketone, isophorone, etc.) did not affect the determination. Therefore, the determination method used with the composite thermal desorption air sampling tube can be used to efficiently and accurately determine the concentration levels of the above 24 common vaporized organic toxins in workplace air. In summary, this technology enables the simultaneous collection and detection of 24 common vaporous organic toxins in workplace air, significantly improving the accuracy and sensitivity of the method. It allows for simultaneous sampling and detection using any sampling method (individual or fixed-point sampling, long-term or short-term sampling), overcoming the drawbacks of current methods that require different air sampling tubes, different desorption solutions for sample pretreatment, and different detection methods. This greatly enhances sampling efficiency and work quality. Furthermore, the developed composite thermal desorption air sampling tube can not only collect the aforementioned 24 common vaporous organic toxins in workplace air but also other common vaporous organic toxins. By optimizing sample thermal desorption conditions and instrument detection conditions, a series of supporting qualitative and quantitative determination methods can be developed. This is expected to enable rapid, efficient, and comprehensive monitoring of the concentration levels of more common vaporous organic toxins in workplace air, and can also provide strong technical support for the effective handling of sudden chemical poisoning incidents caused by common vaporous organic toxins. Therefore, the development of the composite thermal desorption air sampling tube and its supporting determination methods have broad application prospects.

[0039] Reference Figure 2 , Figure 3As a preferred technical solution in this embodiment, the sealing part includes a sealing cover 211, an elastic block 212 and a sealing ring. The elastic block 212 is slidably disposed along the inner wall of the sealing cover, and specifically, the elastic block is slidably disposed radially along the inner cavity of the sealing cover. The sealing ring is disposed on the bottom wall of the inner cavity of the sealing cover 211, and the sealing ring can cooperate with the end of the tube body 10.

[0040] Furthermore, in order to enable the elastic block 212 to move radially along the inner cavity of the sealing cover 211, a limiting groove 213 is opened at the bottom of the sealing cover, and the elastic block 212 is slidably disposed in the limiting groove 213 by means of a spring 214.

[0041] Reference Figure 4 Furthermore, the two end sidewalls of the tube body 10 are provided with annular grooves 110. The annular grooves include an inner bottom wall 111 and an inclined groove 112. The inner bottom wall 111 is distributed in an annular shape on the outer wall of the tube body. The inclined groove starts from the inner bottom wall and extends towards the outer wall of the tube body 10 in a gradually expanding manner. In this way, the inclined groove forms an inclined structure groove on the outer wall of the tube body.

[0042] Furthermore, the end of the tube body 10 is provided with a guide groove 120 communicating with the annular groove 110 along its axial direction. The guide groove 120 is a strip-shaped groove, and the size of the elastic locking block 212 is adapted to the guide groove 120. In use, when it is necessary to connect the sealing cap to the tube body, the driving sealing cover is aligned with the end of the tube body, and the elastic locking block is placed in the guide groove. At this time, the elastic locking block compresses the spring, and then drives the sealing cover to move towards the tube body, so that the elastic locking block moves along the guide groove. As the elastic locking block moves into the annular groove, the elastic locking block is engaged in the inclined groove position of the annular groove under the restoring force of the spring to achieve positioning, thereby achieving the purpose of fixing the sealing cover and the connecting cover on it. At the same time, the sealing ring of the tube body end and the bottom wall of the inner cavity of the sealing cover are installed and matched to achieve the sealing connection between the tube body and the sealing cover.

[0043] In addition, when it is necessary to separate the sealing cap from the tube body 10, the sealing cover is driven to detach from the tube body by external force. At this time, the elastic block 212 compresses the spring and moves through the annular groove to the guide groove, thereby driving the elastic block to move along the guide groove so that the sealing cover moves away from the tube body, thus realizing the separation of the sealing cap from the tube body.

[0044] It should be noted that the depth of the guide groove 120 extending along the side wall of the tube body 10 is less than the depth of the inner bottom wall 111 extending along the side wall of the tube body. In this way, when the elastic block 212 moves downward out of the guide groove 120, it can enter the position of the inner bottom wall 111 under the action of the spring, thereby realizing the engagement of the elastic block with the annular groove, so as to fix the sealing cover with the tube body.

[0045] Reference Figure 3 , Figure 4In some embodiments, the connecting part is a docking cover 221 disposed at the top of the sealing part, which can be connected to the thermal desorption instrument during sample processing.

[0046] The above-described embodiments are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made by those skilled in the art to the technical solutions of the present utility model without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A composite thermal desorption air sampling tube for occupational health, characterized in that, include: The tube body (10) has multiple layers of solid adsorbent arranged sequentially from the inlet end to the outlet end. The multiple layers of solid adsorbent include a first graphitized carbon adsorbent layer, a second graphitized carbon adsorbent layer, a third graphitized carbon adsorbent layer, and a carbon molecular sieve adsorbent. A sealing cap (20) is also provided at both ends of the tube body (10). The sealing cap includes a sealing part connected to the tube body (10) and a connecting part integrally formed with the sealing part. A protective layer is also provided at both ends of the tube body (10). The pore size of the protective layer is smaller than the particle size of the solid adsorbent. The protective layer is made of stainless steel wire or silanized glass wool. The first graphitized carbon adsorbent layer has a particle size of 20-40 mesh and a specific surface area of ​​20 μm. 2 / g of graphitized carbon adsorbent, wherein the second graphitized carbon adsorbent layer has 50-120mg of graphitized carbon with a particle size of 20-40 mesh and a specific surface area of ​​130m. 2 / g of graphitized carbon adsorbent, wherein the third graphitized carbon adsorbent layer has 50-120mg of material, a particle size of 20-40 mesh, and a specific surface area of ​​240m. 2 / g of graphitized carbon adsorbent, wherein the carbon molecular sieve adsorbent has a particle size of 20-40 mesh and a specific surface area of ​​1200m. 2 / g of carbon molecular sieve adsorbent.

2. The composite thermal desorption air sampling tube for occupational health as described in claim 1, characterized in that, The sealing part includes a sealing cover (211), an elastic locking block (212) that slides along the inner wall of the sealing cover, and a sealing ring that is disposed on the bottom wall of the inner cavity of the sealing cover (211) and can cooperate with the end of the tube body (10).

3. The composite thermal desorption air sampling tube for occupational health as described in claim 2, characterized in that, The two end sidewalls of the tube (10) are provided with annular grooves (110). The annular grooves include an inner bottom wall (111) and an inclined groove (112) that extends from the inner bottom wall to the outer wall of the tube (10) in a gradually expanding manner. The end of the tube (10) is provided with a guide groove (120) that communicates with the annular groove (110) along its axial direction.

4. The composite thermal desorption air sampling tube for occupational health as described in claim 3, characterized in that, The size of the elastic block (212) is adapted to the guide groove (120).

5. The composite thermal desorption air sampling tube for occupational health as described in claim 4, characterized in that, The connecting part is a docking cover (221) located at the top of the sealing part.

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