A new sensor for detecting the content of trichloroethylene gas in air

Abstract

The application discloses a novel sensor for detecting the content of trichloroethylene gas in air. The existing detection method is tedious, time-consuming, and the instrument is complex and expensive, and the solvent used can cause certain harm to the human body and the environment. According to the principle of thermal desorption, a thermal desorption instrument is added, and a novel instrument system of thermal desorption / chemiluminescence combined technology is self-assembled. The application has the advantages of good selectivity, high sensitivity, simple operation, short time consumption and the like. The application has good application prospect for detecting trichloroethylene gas in air.

Description

Technical Field

[0001] This invention relates to a novel sensor for detecting the content of trichloroethylene gas in the air, belonging to the field of detection method invention technology. Background Technology

[0002] Trichloroethylene (TCE) is a colorless, transparent liquid with a chloroform-like odor. It is an important industrial chlorine solvent, liquid at room temperature, and primarily used as a degreasing agent, dry cleaning agent, and extractant. Exposure to trichloroethylene is mainly occupational; it can occur during its manufacture, storage, and use, particularly among workers in the electroplating, hardware, stainless steel products, and electronics industries. Trichloroethylene has an anesthetic effect on the central nervous system, affects the liver to varying degrees, and can cause sudden death. It is also carcinogenic.

[0003] Currently, there are few methods for determining the content of trichloroethylene in the air, mainly gas chromatography (GC). However, GC requires programmed temperature rise and a dissolving medium, using an inert gas such as helium as a carrier gas. This method is cumbersome, time-consuming, and requires complex and expensive equipment. Furthermore, GC uses highly toxic solvents such as carbon disulfide and chloroform, posing health hazards to operators. Alternatively, the pyridine-base colorimetric method can be used, but because the reaction is not specific, the presence of carbon tetrachloride or chloroform in the environment can interfere with the results. This method also uses the highly odorous pyridine as an absorbent and employs porous glass plate absorption tubes for sampling, making it inconvenient to carry and analyze, thus limiting its practicality. This invention first uses a thermal desorption / chemiluminescence coupled instrument system to study the catalytic luminescence behavior of trichloroethylene under nano-zinc oxide catalysis using Tenax-GR as the adsorbent. The study shows that this method is simple and rapid, with high sensitivity and excellent selectivity. Summary of the Invention

[0004] The purpose of this invention is to provide a detection device that is simple to operate, has good selectivity, and high sensitivity for monitoring the content of trichloroethylene gas in the air.

[0005] (1) Weigh a certain amount of adsorbent Tenax-GR, fix the adsorbent in the middle of a glass tube of suitable size with both ends connected with an appropriate amount of glass wool, and then connect it to the air inlet tube of the atmospheric sampler.

[0006] Weigh out 0.7-1.0g of the adsorbent.

[0007] (2) Weigh out a certain amount of zinc oxide and yttrium oxide nanomaterials respectively, mix the two materials evenly in a mortar and grind them, then place them on a clean glass plate, and use a clean knife to spread the mixed catalyst material into a width equal to the length of the soldering iron core (35W). Then evenly apply an appropriate amount of glue to the ceramic outer layer of the soldering iron core. When the glue is half dry, the catalyst material can be adhered to the ceramic surface. Try to make the catalyst material adhere evenly to the ceramic surface, and the surface of the prepared catalyst rod should be as smooth as possible. Firing the prepared catalyst rod on an electronic energy-saving temperature controller. At the beginning, adjust the voltage to a certain value, and after about half an hour, slowly increase the voltage to 190-250V. The total firing time is 1-2 hours.

[0008] The mass ratio of nano ZnO and nano Y2O3 is 2:1, and the total mass is 0.8-0.1g.

[0009] (3) At room temperature and pressure (298 K, 1.01 × 10⁵ Pa), 0.2 μL of liquid trichloroethylene (AR grade) was measured using a microsyringe and injected into a pre-sealed 10 L clean container for gas mixing. After standing for a few minutes, samples were taken using a Tenax-GR adsorption tube. Sampling was performed for 20 minutes at a flow rate of 0.5 L / min, i.e., 10 L was sampled. At this point, the concentration of trichloroethylene was 29.3 mg / m³. 3 .

[0010] (4) Place the sampled adsorption tube into a thermal desorption instrument and desorb it by heating for 300s. The desorption is carried into the reaction chamber by air. The generated catalytic luminescence signal is detected and processed by a photoelectric detection and data processing system. (Note: Before the experiment, heat the catalytic material to 400-600℃ and keep it for 10-20min to eliminate the influence of the original adsorbate.) (5) Selection of optimal catalytic chemiluminescence conditions: ① Change the temperature of thermal desorption while keeping other conditions unchanged.

[0011] ② Change the catalytic temperature while keeping other conditions constant.

[0012] ③ Change the wavelength of the filter while keeping other conditions unchanged.

[0013] (6) Using the method in step (3), trichloroethylene gas of different known concentrations was prepared. Then, under the optimal conditions explored above, a working curve showing the relationship between trichloroethylene gas concentration and chemiluminescence intensity was plotted. The specific conditions of this invention are as follows: The simple device for detecting the trichloroethylene gas content in the air provided by the present invention has the following advantages: (1) The present invention has good selectivity for the detection of trichloroethylene gas in the air (see Figure 1 The method of this invention has high sensitivity.

[0014] (2) The equipment and instruments required for this invention are low in cost and occupy little space (see Figure 5 ). Attached Figure Description

[0015] Figure 1 This invention provides a comparison of the catalytic luminescence intensity of different gases on the nano-ZnO-Y2O3 sensing material in an embodiment of the invention (under the same reaction conditions and with each gas concentration of 29.3 mg / m³). 3 ); Figure 2 This is an X-ray powder diffraction pattern of the nanomaterial in an embodiment of the present invention; Figure 3 Here are SEM images of the nanomaterials in an embodiment of the present invention; Figure 4 This is a linear relationship graph between the concentration of trichloroethylene gas and the luminescence intensity in an embodiment of the present invention; Figure 5 This is a schematic diagram of the sensing system structure in an embodiment of the present invention. Detailed Implementation Example 1

[0016] (1) Weigh 0.8g of adsorbent Tenax-GR, fix the adsorbent in the middle of a glass tube of suitable size with both ends open with an appropriate amount of glass wool, and then connect it to the air inlet tube of the atmospheric sampler.

[0017] (2) Weigh 0.5g of zinc oxide and 0.3g of yttrium oxide nanomaterials respectively, mix the two materials evenly in a mortar and grind them, then place them on a clean glass plate, and use a clean knife to spread the mixed catalyst material evenly to the same width as the length of the soldering iron core (35W). Then evenly apply an appropriate amount of glue to the ceramic outer layer of the soldering iron core. When the glue is half dry, the catalyst material can be adhered to the ceramic surface. Try to make the catalyst material adhere evenly to the ceramic surface, and the surface of the prepared catalyst rod should be as smooth as possible. Firing the prepared catalyst rod on an electronic energy-saving temperature controller. At the beginning, the voltage is set to a certain value, and after about half an hour, the voltage is slowly increased to 250V. The total firing time is 2 hours.

[0018] (3) At room temperature and pressure (298K, 1.01×105Pa), an atmospheric sampler with an adsorption tube (Tenax.GR adsorbent) was used to sample the gas in a workshop containing trichloroethylene for 20 minutes (flow rate of 0.5 L / min), i.e., 10 liters were sampled.

[0019] (4) The sampled adsorption tube was placed in a thermal desorption instrument and desorbed by heating at 130°C for 300s. The sample was then carried into the reaction chamber by air. The catalytic luminescence signal generated under the catalytic environment at 210°C was detected and processed by a photoelectric detection and data processing system through a 440nm wavelength filter. The concentration of trichloroethylene gas in the sample was calculated based on the intensity of the luminescence signal and the relevant working curve.

Claims

1. A novel sensor for detecting the content of trichloroethylene gas in air, characterized in that, Includes the following equipment and materials: 1) One thermal desorption instrument, employing thermal desorption / chemiluminescence coupled technology; 2) Organic polymers as adsorbent materials; 3) A mixture of nano-ZnO and Y2O3 is used as a sensing material.

2. The novel sensor for detecting the trichloroethylene gas content in air according to claim 1, characterized in that, The organic polymer is one or a mixture of Tenax-GR, Tenax-GC and Tenax-TA as the adsorbent material.

3. A novel sensor for detecting the content of trichloroethylene gas in air according to claim 1, characterized in that, The mass ratio of nano-ZnO to Y2O3 is 5:

3.

4. A novel sensor for detecting the content of trichloroethylene gas in air according to claim 1, characterized in that, The mass of the adsorbent used is 0.7–1.2 g.

5. A novel sensor for detecting the content of trichloroethylene gas in air according to claim 1, characterized in that, The Y2O3 and ZnO used are both nanomaterials with a particle size of 20-50 nm.

6. A novel sensor for detecting the content of trichloroethylene gas in air according to claim 1, characterized in that, The specific steps for preparing the ZnO-Y2O3 mixed material are as follows: Weigh out 0.4–0.7 g of nano ZnO and 0.2–0.4 g of nano Y2O3, mix them evenly in a mortar, and then place them on a clean glass plate. Use a clean knife to spread the mixture to a width equal to the length of the ceramic heating tube (35W). Apply an appropriate amount of glue evenly to the surface of the ceramic heating tube. When the glue is semi-dry, the mixture can be adhered to the ceramic surface, ensuring that the mixture adheres evenly to the ceramic surface. Finally, fire it at 400–500℃ for 1–2 hours on an electronic energy-saving temperature controller.

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