A method for detecting pyridine in air

Abstract

The present invention relates to a method for detecting pyridine in air. A test strip is placed in an air environment to be tested, and a color change of the test strip is observed. The pyridine concentration is qualitatively or quantitatively determined based on the color change of the test strip. The test strip is made of filter paper and a zinc-based organic-inorganic hybrid halide material. The present invention uses the test strip and a color card or a linear correlation model standard curve to perform qualitative or semi-quantitative determination of the pyridine concentration in the air, thereby monitoring whether the pyridine content in the air exceeds the standard or the extent of the excess. The method has the advantages of easy operation and more convenient detection.

Description

Technical Field

[0001] The invention relates to a method for detecting pyridine in the air, belonging to the technical field of pyridine detection. Background Art

[0002] Pyridine is an important solvent and intermediate in pharmaceutical synthesis and a crucial additive in fuels, rubber products, paints, and pesticides. However, due to its volatility, pyridine can be released into the environment during the synthesis of these industrial products, posing a threat to human health. Studies have shown that short-term exposure to pyridine vapor can damage the human respiratory and nervous systems, causing symptoms such as dizziness, nausea, laryngitis, respiratory distress, and vomiting. Long-term exposure to pyridine can also cause damage to the liver, heart, and kidneys. The carcinogenicity of pyridine has been confirmed in animal studies, and the International Agency for Research on Cancer has classified pyridine as a carcinogen (Group 2B).

[0003] Pyridine detection mainly relies on gas chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, fiber optic sensors and potentiometric sensors.

[0004] In the Chinese invention patent application with application publication number CN112305102A, entitled “A method for detecting and analyzing residual solvent pyridine in solid salts”, a method for detecting and analyzing residual solvent pyridine in solid salts is disclosed, which comprises the following steps: Step 1, solid sample pretreatment: after the solid sample is weighed and dissolved, it is placed in a glass sample bottle, mixed and placed, and after it is completely dissolved, the pH value of the sample solution is adjusted, and at the same time, the sample is exposed to less air, and parallel experiments are performed; 5-9 ml of sample solution is added to the sample bottle for headspace sampling to be tested; Step 2, analysis and detection: (1) drawing a standard curve. The method for drawing a standard curve described herein can adopt the standard curve commonly used in existing detection and analysis. The concentration of the selected standard solution is not limited; (2) the sample solution to be tested, which has been treated in step 1, is placed in an injection bottle and detected by GC-MS; (3) the standard concentrations of pyridine are configured to be 10 ppb, 20 ppb, 50 ppb, 100 ppb, and 200 ppb. The concentrations of several standards of the standard curve are also realized in the headspace sample bottle. According to the conditions of the instrument, the samples are injected and analyzed in sequence from low concentration to high concentration, and the retention time and response value of pyridine are recorded; the standard curve is established with the pyridine concentration as the horizontal axis and its response value as the vertical axis.

[0005] For example, in the Chinese invention patent application with application publication number CN111562330A, entitled “Method for determining the content of pyridine in industrial wastewater”, a method for determining the content of pyridine in industrial wastewater is disclosed, which is characterized by comprising: S100, a step of preparing a standard series of solutions: accurately weighing 100 mg of a pyridine standard in a 100 mL volumetric flask pre-filled with a small amount of pure water, diluting the volume to 100 mL to obtain a standard stock solution with a concentration of 1000 mg / L, transferring the solution to a sample bottle and sealing the bottle at 4°C; respectively taking a certain amount of the standard stock solution and preparing the standard stock solutions with concentrations of 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L with pure water. .00mg / L, 2.00mg / L, 5.00mg / L standard series solutions; S200, standard curve drawing steps: take 10mL of the prepared standard series solutions from low concentration to high concentration and place them in a 20mL headspace bottle, and add 2-3g of sodium chloride respectively. After sealing, measure according to the set analysis conditions, and establish a univariate linear regression standard curve with the peak area as the ordinate and the corresponding pyridine concentration as the abscissa; wherein the set analysis conditions include: injection through the headspace sampler under the conditions of equilibrium temperature of 90℃, equilibrium time of 15min, sample loop temperature of 110℃, and transmission line temperature of 120℃, with the injection port temperature of 200℃, FID detector temperature of 250℃, hydrogen flow rate of 40mL / min, and air flow rate of 400mL / min. min, a tail gas flow rate of 30 mL / min, and a split ratio of 10:1 are used for analysis and detection by gas chromatograph; S300, a sample determination step, the sample determination step comprising: S301, a water sample analysis test: 10 mL of the water sample to be tested is placed in a 20 mL headspace bottle, and the same amount of sodium chloride as in step S200 is added, and the analysis test is performed under the same analysis conditions as step S200; S302, a blank sample analysis test: 10 mL of a blank control sample is placed in a 20 mL headspace bottle, and the same amount of sodium chloride as in step S200 is added, and the analysis test is performed under the same analysis conditions as step S200; S400, a sample concentration calculation step: based on the pyridine concentration obtained in the standard curve, the concentration of pyridine in the sample is calculated according to the standard calculation equation.

[0006] The above detection methods are relatively complicated, take a relatively long time to detect, and usually require professional personnel to operate.

[0007] Based on the above issues, the applicant conducted research, which led to the present case. Summary of the Invention

[0008] The object of the present invention is to provide a method for detecting pyridine in the air which is easy to operate and quicker to detect.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for detecting pyridine in the air comprises placing a test paper in an air environment to be detected, observing the color change of the test paper, and qualitatively or quantitatively determining the pyridine concentration based on the color change of the test paper.

[0011] The test strips are prepared in the following manner:

[0012] Step 1: 4.00-6.00 mmol of 5-bromoquinoline and 4.00-6.00 mmol of 4-triphenylamine borate are added to a container containing 15-20.0 mL of tetrahydrofuran. 0.40-0.50 g of potassium carbonate or sodium carbonate is dissolved in 4.0-5.0 mL of water and added to the container. 0.08-0.12 mmol of tetrakis(triphenylphosphine)palladium is then added to the container. Under nitrogen protection, the mixture is stirred at 70-80°C for 42 to 54 hours. After completion of the reaction, the mixture is diluted with water, the organic layer is separated, and the crude product is concentrated under reduced pressure to obtain a colorless powder intermediate (hereinafter referred to as 5-DQL).

[0013] Step 2: 0.10-0.30 mmol of the intermediate product was dissolved in 8.0-10.0 mL of acetonitrile, followed by the addition of 40.0-50.0 μL of hydroiodic acid. 0.10-0.30 mmol of zinc iodide was dissolved in 2.0-3.0 mL of deionized water. The two solutions were mixed and dissolved, and the mixture was allowed to stand to allow the acetonitrile to fully evaporate. The solid was collected, washed, and dried to obtain the target final product (hereinafter referred to as OIMHs, i.e. ;

[0014] Step 3: Disperse 1.0-3.0 mg of the target final product in 0.5-1.5 mL of n-hexane and perform ultrasonic treatment to form a uniformly mixed dispersion. Immerse the filter paper in the dispersion and perform ultrasonic treatment to uniformly distribute the dispersion on the filter paper. Dry at room temperature to form the test paper.

[0015] As a preferred embodiment of the present invention, the diameter of the test paper is 0.7-0.9 cm, and the loading amount of the target end product in the test paper is 1.38 mg to 1.42 mg.

[0016] As a preferred embodiment of the present invention, in step 1, after the reaction is completed, dilute with water and extract with ethyl acetate, retain the organic layer, add an equal volume of water, shake, let stand and separate, discard the aqueous layer, retain the organic layer, then add an equal volume of saturated brine, shake, let stand and separate, discard the brine layer, retain the organic layer, transfer the organic layer into a conical flask, add sufficient anhydrous sodium sulfate to dry, filter, and concentrate the filtrate under reduced pressure to obtain the crude product.

[0017] As a preferred embodiment of the present invention, in step 1, silica gel column chromatography is used for purification, with petroleum ether and ethyl acetate as eluents, and the volume ratio of the two is 5:1.

[0018] As a preferred embodiment of the present invention, in step 2, the standing time is more than 48 hours, the collected solid is washed three times with water and acetonitrile in sequence, and dried in vacuo at 50°C to obtain the target final product.

[0019] As a preferred embodiment of the present invention, in step three, the target final product is dispersed in n-hexane, the ultrasonic treatment time is 5 minutes, the frequency is 35kHz, and the filter paper is immersed in the above dispersion, and the ultrasonic treatment time is 1 minute, the frequency is 35kHz.

[0020] As a preferred embodiment of the present invention, in step three, the filter paper is immersed in the above dispersion, ultrasonically treated so that the dispersion is evenly distributed on the filter paper and dried at room temperature. This process is repeated three times to form the test paper.

[0021] As a preferred embodiment of the present invention, during the test, the test paper is exposed to the air for 20 minutes.

[0022] As a preferred embodiment of the present invention, the qualitative determination of pyridine concentration is to pre-prepare a color card, which is prepared in the following manner: pyridine is injected into the air to form air with different pyridine concentrations, and a test paper is placed in the air with different pyridine concentrations for 20 minutes, and the color corresponding to the test paper is made on the color card.

[0023] As a preferred embodiment of the present invention, the quantitative determination of pyridine concentration is to inject pyridine into the air to form air with different pyridine concentrations, and place the test paper in the air with different pyridine concentrations for 20 minutes, irradiate with a handheld ultraviolet lamp with a wavelength of 365 nm, take pictures to obtain images, extract the RGB values ​​of the image through the color picking APP software, select the ratio of the red channel to the green channel as the ordinate, and the pyridine concentration as the abscissa, and draw a linear correlation model standard curve. During the test, the test paper image is obtained by taking a picture, and the RGB value of the image is extracted through the color picking APP software, and the ratio of the red channel to the green channel is calculated as the ordinate value. The corresponding abscissa value is found on the linear correlation model standard curve as the pyridine concentration.

[0024] After adopting the technical solution of the present invention, the target final product ( Protonated 5-DQL molecules As a cationic skeleton, zinc halide is an anion. Since pyridine vapor has Lewis basicity, it can react with Proton exchange is carried out, thereby destroying the original structure of the hybrid material, thereby achieving efficient sensing of pyridine, that is, the pyridine molecule approaches When the organic cationic skeleton is induced )from Break away from it, trigger The conformation of the cation rearranges to form The intermediate undergoes a high energy transition state at this stage, so it has a long sensing time of about 40s. During this stage, the fluorescence color gradually changes from yellow to orange. As the exposure time in pyridine increases, the pyridine and Proton exchange occurs to produce an intermediate with red fluorescence Since this process undergoes a transition state with lower energy, red fluorescence can be observed after only 20 seconds of exposure to pyridine (i.e., a total of 60 seconds). As the exposure time in pyridine vapor increases, the red fluorescence in the material increases. Further proton exchange with pyridine occurs, and finally non-fluorescent The present invention uses a test strip and a color card or a linear correlation model standard curve to perform qualitative or semi-quantitative determination of pyridine concentration in the air, thereby monitoring whether the pyridine content in the air exceeds the standard or the extent of the excess, with the advantages of easy operation and more convenient detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the color card in the present invention.

[0026] Figure 2 This is a standard curve diagram of the linear correlation model in the present invention (the horizontal axis in the figure represents the pyridine concentration in ppm, and the vertical axis represents the ratio of the red channel to the green channel, that is, the R / G value). DETAILED DESCRIPTION

[0027] In order to better understand the technical solution of the present invention, it is described in more detail below with reference to embodiments.

[0028] (1) Synthesis of N,N-diphenyl-4-(quinolin-5-yl)aniline (5-DQL)

[0029] Add 4.00-6.00 mmol of 5-bromoquinoline (CAS No. 4964-71-0) and 4.00-6.00 mmol of 4-triphenylamine borate (CAS No. 201802-67-7) to a flask containing 15-20.0 mL (20.0 mL in the example) of tetrahydrofuran (THF). Separately, dissolve 0.40-0.50 g of potassium carbonate or sodium carbonate (0.50 g of potassium carbonate was used in the example) in 4.0-5.0 mL (5 mL in the example) of water, then mix the two solutions. Then, add 0.08-0.12 mmol (0.10 mmol in the example) of tetrakis(triphenylphosphine)palladium (CAS No. 14221-01-3) to the mixture. Stir the reaction at 70-80°C under nitrogen for 42 to 54 hours (75°C for 48 hours in the example). After the reaction is complete, the mixture is diluted with water and extracted with ethyl acetate. The organic layer is separated and retained. An equal volume of water is added, the mixture is shaken, and the stratification is allowed to proceed. The aqueous layer is discarded, and the organic layer is separated and retained. An equal volume of saturated brine is added, the mixture is shaken, and the stratification is allowed to proceed. The brine layer is discarded, and the organic layer is separated and retained. The resulting organic layer is transferred to a conical flask, dried over anhydrous sodium sulfate, filtered, and the filtrate is concentrated under reduced pressure to obtain the crude product. The crude product is purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 5 / 1, v / v). The intermediate 5-DQL is obtained as a colorless powder.

[0030] Under the same conditions, the yield of 5-DQL from the reaction of 5-bromoquinoline (4.00 mmol) and 4-triphenylamine borate (6.00 mmol) was 86.7%; the yield from the reaction of 5-bromoquinoline (5.00 mmol) and 4-triphenylamine borate (4.00 mmol) was 79.6%; and the yield from the reaction of 5-bromoquinoline (6.00 mmol) and 4-triphenylamine borate (5.00 mmol) was 95.3%. The highest yield was obtained from the reaction of 5-bromoquinoline (6.00 mmol) and 4-triphenylamine borate (5.00 mmol).

[0031] (2) Synthesis of zinc-based organic-inorganic hybrid halides (OIMHs) Dissolve 5-DQL (0.10 – 0.30 mmol) in 8.0-10.0 mL (10.0 mL in the example) of acetonitrile, then add 40.0-50.0 μL of hydroiodic acid (50.0 μL of 57% hydroiodic acid in the example). ) was dissolved in 2.0-3.0 mL (3.0 mL in the embodiment) of deionized water. The two solutions were mixed and ultrasonicated until completely dissolved. The resulting mixture was allowed to stand for more than 48 hours (48 hours in the embodiment) to allow the acetonitrile to fully evaporate. The solid precipitated at the bottom of the beaker was collected, washed three times with water and acetonitrile in sequence, and dried under vacuum at 50°C to obtain the target OIMHs. .

[0032] Under the same other conditions, the yield of the product obtained by the reaction of 5-DQL (0.20 mmol) and zinc iodide (0.10 mmol) was 40.2%; the yield of the product obtained by the reaction of 5-DQL (0.30 mmol) and zinc iodide (0.20 mmol) was 47.7%; and the yield of the product obtained by the reaction of 5-DQL (0.10 mmol) and zinc iodide (0.30 mmol) was 50.2%.

[0033] (3) Preparation of filter paper-based test strips

[0034] Take 1.0-3.0 mg (2 mg in the example) Disperse in 0.5-1.5 mL (0.5 mL in the example) of n-hexane and sonicate for 5 minutes (operating frequency is 35 kHz) to ensure uniform distribution of the hybrid material. Then immerse a circular filter paper with a diameter of 0.7 to 0.9 cm (0.8 cm in the example) in the above dispersion and sonicate for 1 minute (operating frequency is 35 kHz). Remove and air dry at room temperature. Repeat the above immersion-drying process 3 times. Other conditions remain the same. (1.0 mg) was dispersed in 1.5 mL of n-hexane, and the loading on a single filter paper was 0.78 ± 0.15 mg; (2.0 mg) was dispersed in 0.5 mL of n-hexane, and the loading on a single filter paper was 1.4 ± 0.2 mg; (3.0 mg) was dispersed in 1.0 mL of n-hexane, and the loading amount on a single filter paper was 1.52 ± 0.1 mg. The filter paper obtained by dispersing 2.0 mg in 0.5 mL of n-hexane (i.e., the test paper) is the most uniform, with a single-sheet loading of 1.4±0.2 mg.

[0035] Actual sample testing: Expose the sample to air (containing pyridine) for 18 to 22 minutes (20 minutes in the present embodiment). Illuminate with a flashlight at a wavelength of 365 nm and then take a photograph. Use the Color Grab app (an existing color picking tool) to select the color. Other color picking software can also be used. Select the center area of ​​the test paper (diameter ≥ 0.5 cm) to obtain the RGB value. Calculate the red / green channel ratio (R / G). Read the corresponding pyridine concentration against a color chart, or find the corresponding abscissa by comparing the ordinate of the linear correlation model standard curve. This abscissa value is the pyridine concentration.

[0036] The process of making a standard color card is as follows:

[0037] A syringe was used to inject pyridine solutions of varying concentrations (5.0, 10.0, 30.0, 50.0, 70.0, 100.0, 200.0, 300.0, 400.0, 500.0, 600.0, 700.0, and 800.0, all in ppm) into a flask in the experimental setup. After the solvent completely evaporated, vapor was generated and diffused into another flask containing a test strip, and a timer was started. The test strip was exposed to the pyridine vapor for 20 minutes. After removal, the strip was immediately illuminated with a 365 nm handheld UV lamp, and an image of the strip was captured using a smartphone camera.

[0038] Take a test strip image for each concentration and make the corresponding color on the color card (see attached Figure 1 shown).

[0039] Then, the RGB value of the image was extracted using the color picking app. The ratio of the red channel to the green channel (R / G) was selected as the vertical axis, and the pyridine concentration (the pyridine concentration in the air was converted by the pyridine injection volume and the volume of the flask) was selected as the horizontal axis. A linear correlation model standard curve was constructed (see the attached figure). Figure 2 ), enabling visual semi-quantitative detection of pyridine levels.

[0040] The present invention can also use other experimental devices to create air with different pyridine concentrations, place test strips in the experimental device to show different colors, and make color cards or collect RGB values ​​to draw a standard curve.

[0041] The protection scope of the present invention is not limited to this embodiment, and any similar changes made thereto shall not depart from the protection scope of the present invention.

Claims

1. A method for detecting pyridine in air, characterized in that: Place the test paper in the air environment to be tested, observe the color change of the test paper, and qualitatively determine the pyridine concentration or semi-quantitatively determine the pyridine concentration based on the color change of the test paper; The test strips are prepared in the following manner: Step 1: 4.00-6.00 mmol of 5-bromoquinoline and 4.00-6.00 mmol of 4-triphenylamine borate are added to a container containing 15-20.0 mL of tetrahydrofuran. 0.40-0.50 g of potassium carbonate or sodium carbonate is dissolved in 4.0-5.0 mL of water and added to the container. 0.08-0.12 mmol of tetrakis(triphenylphosphine)palladium is then added to the container. Under nitrogen protection, the mixture is stirred at 70-80°C for 42 to 54 hours. After the reaction is complete, the mixture is diluted with water, the organic layer is separated, and the crude product is obtained by concentration under reduced pressure. The crude product is purified to obtain a colorless powder intermediate product 5-DQL. Step 2: Dissolve 0.10–0.30 mmol of the intermediate product 5-DQL in 8.0–10.0 mL of acetonitrile, then add 40.0–50.0 μL of hydroiodic acid. Dissolve 0.10–0.30 mmol of zinc iodide in 2.0–3.0 mL of deionized water. Mix and dissolve the two solutions. Allow to stand to allow the acetonitrile to evaporate completely. Collect the solid, wash, and dry to obtain the target final product (5-DQL-H)2ZnI4. Step 3: Disperse 1.0-3.0 mg of the target final product (5-DQL-H)2ZnI4 in 0.5-1.5 mL of n-hexane and sonicate to form a uniformly mixed dispersion. Immerse a filter paper in the dispersion and sonicate to evenly distribute the dispersion on the filter paper. Dry at room temperature to form the test paper. The qualitative determination of pyridine concentration is performed by pre-making a color card, which is made by injecting pyridine into the air to form air with different pyridine concentrations, and placing a test paper in the air with different pyridine concentrations for 20 minutes, and making the color corresponding to the test paper on the color card; The semi-quantitative determination of pyridine concentration is as follows: pyridine is injected into the air to form air with different pyridine concentrations, and a test strip is placed in the air with different pyridine concentrations for 20 minutes, irradiated with a handheld ultraviolet lamp with a wavelength of 365 nm, photographed to obtain an image, and the RGB value of the image is extracted by the color picking APP software. The ratio of the red channel to the green channel is selected as the ordinate, and the pyridine concentration is used as the abscissa to draw a linear correlation model standard curve. During the test, the test strip image is obtained by photographing, and the RGB value of the image is extracted by the color picking APP software. The ratio of the red channel to the green channel is calculated as the ordinate value, and the corresponding abscissa value is found on the linear correlation model standard curve as the pyridine concentration.

2. A method for detecting pyridine in air according to claim 1, characterized in that: The diameter of the test paper is 0.7-0.9 cm, and the loading amount of the target final product (5-DQL-H)2ZnI4 in the test paper is 1.38 mg to 1.42 mg.

3. A method for detecting pyridine in air according to claim 2, characterized in that: In step 1, after the reaction is completed, dilute with water and extract with ethyl acetate, retain the organic layer, add an equal volume of water, shake, let stand and separate, discard the aqueous layer, retain the organic layer, then add an equal volume of saturated brine, shake, let stand and separate, discard the brine layer, retain the organic layer, transfer the organic layer to a conical flask, add sufficient anhydrous sodium sulfate to dry, filter, and concentrate the filtrate under reduced pressure to obtain the crude product.

4. A method for detecting pyridine in air according to claim 3, characterized in that: In step 1, purification was performed by silica gel column chromatography using petroleum ether and ethyl acetate as eluents in a volume ratio of 5:

1.

5. A method for detecting pyridine in air according to claim 4, characterized in that: In step 2, the standing time is more than 48 hours, and the collected solid is washed three times with water and acetonitrile in sequence, and dried in vacuo at 50°C to obtain the target final product (5-DQL-H)2ZnI4.

6. A method for detecting pyridine in air according to claim 5, characterized in that: In the step three, the target final product (5-DQL-H)2ZnI4 is dispersed in n-hexane, and the ultrasonic treatment time is 5 minutes and the frequency is 35kHz. The filter paper is immersed in the above dispersion and the ultrasonic treatment time is 1 minute and the frequency is 35kHz.

7. A method for detecting pyridine in air according to claim 6, characterized in that: In step three, the filter paper is immersed in the dispersion, ultrasonically treated to make the dispersion evenly distributed on the filter paper, and then dried at room temperature. This process is repeated three times to form the test paper.

8. A method for detecting pyridine in air according to claim 7, characterized in that: During the test, the test strips are exposed to air for 18-22 minutes.

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