A ratio fluorescent test paper capable of detecting formaldehyde exposure in real time, a preparation method, a detection method and applications

Abstract

The application provides a ratiometric fluorescent test paper capable of detecting formaldehyde exposure in real time, a preparation method, a detection method and application, relates to the field of formaldehyde detection, and comprises the following steps: injecting an aqueous solution containing acetylacetone, ammonium acetate, glacial acetic acid, ethanol and blue fluorescent carbon dot powder (440 nm) into an ink cartridge, and performing inkjet printing of the aqueous solution on cellulose paper, so that the ratiometric fluorescent test paper is obtained. Based on the solid-phase fluorescence inner filter effect and the Han relaxation reaction, a formaldehyde ratiometric fluorescent sensing strategy is constructed, so that efficient, sensitive and visual on-site detection of formaldehyde is realized.

Description

Technical Field

[0001] This invention relates to the field of formaldehyde detection, and more specifically, to a ratio fluorescent test strip capable of real-time detection of formaldehyde exposure, its preparation method, detection method, and application. Background Technology

[0002] Formaldehyde pollution has long been a major concern as a highly hazardous indoor air pollutant. Formaldehyde is colorless at room temperature, has a pungent odor, is flammable and highly reactive, and is readily soluble in water, ethanol, ether, and acetone. Inhaling small amounts of formaldehyde can irritate the eyes, nasal cavity, and upper and lower respiratory tracts (potentially causing corrosive burns to the mouth, throat, and digestive tract), and cause skin allergies. Long-term exposure increases the risk of pneumonia, leukemia, cancer, and asthma.

[0003] Formaldehyde sources can be mainly divided into outdoor and indoor sources. Generally, indoor formaldehyde exposure is higher than outdoor exposure, primarily due to more sources and lower air exchange rates in the indoor environment. Potential sources of formaldehyde in the indoor environment are numerous, including wood products, paints, electronic devices, paper, textile dyes, inks, and cosmetics. Therefore, reliable, in-situ, and rapid on-site testing of these formaldehyde-producing items and the formaldehyde content in indoor air is crucial.

[0004] Currently, various formaldehyde detection methods have been developed, including spectrophotometry, gas chromatography, high-performance liquid chromatography, electrochemical sensors, Raman spectroscopy, and fluorescence analysis. However, implementing these technologies requires bulky and expensive laboratory equipment and well-trained professionals, and most require cumbersome sample pretreatment. These issues limit the efficiency and sensitivity of formaldehyde detection in the field. Compared with traditional detection methods, colorimetric and fluorescence colorimetric methods have advantages such as simple operation, high specificity, and visualization. However, existing detection methods still have many shortcomings: (1) Based on a single color intensity change, not only is the visualization effect poor and the sensitivity low, but it is also easily affected by the color of the sample itself. (2) The sensor is relatively sensitive to environmental conditions (such as temperature and humidity), which may affect the accuracy of the detection results. In particular, under different climatic conditions, the change in formaldehyde concentration may be amplified by error. (3) Most existing technologies are fixed-point detection types and cannot provide long-term continuous monitoring data. Especially in scenarios where continuous monitoring of occupational exposure and indoor air quality is required, it is impossible to provide timely feedback on changes in formaldehyde concentration. Summary of the Invention

[0005] The purpose of this invention is to provide a ratio fluorescence test strip that can detect formaldehyde exposure in real time. Based on the solid-phase fluorescence internal filtration effect and Hanchback reaction, a formaldehyde ratio fluorescence sensing strategy is constructed to achieve efficient, sensitive, and visual on-site detection of formaldehyde.

[0006] Another objective of this invention is to provide a method for preparing a ratio fluorescent test strip capable of real-time detection of formaldehyde exposure. The method involves loading acetylacetone, ammonium acetate, glacial acetic acid, ethanol, and blue fluorescent carbon dots onto cellulose test strip using inkjet printing to form the formaldehyde test strip. This test strip is simple to prepare and easy to carry.

[0007] The third objective of this invention is to provide a method for detecting formaldehyde based on ratio fluorescence test strips. By detecting the change in fluorescence color of the ratio fluorescence test strips, a simple and sensitive on-site detection of formaldehyde content in complex matrix samples can be achieved without the need for complex and cumbersome sample pretreatment processes.

[0008] The fourth objective of this invention is to provide an application of ratio fluorescent test strips, which are fixed to wearable devices to monitor the cumulative dose of formaldehyde in a human body within a day in real time, enabling the assessment of formaldehyde exposure for workers in specific locations (such as decorators, hairdressers, factory workers, etc.) and thus providing better protection.

[0009] The technical problem solved by this invention is achieved by the following technical solution.

[0010] On one hand, embodiments of the present invention provide a ratio fluorescent test strip capable of real-time detection of formaldehyde exposure, comprising the following steps:

[0011] Ethylenediamine and citric acid were dissolved in ultrapure water and added to a high-pressure reactor. The mixture was reacted at 200°C for 4-5 h. The product was purified by silica gel column chromatography and lyophilized to obtain blue fluorescent carbon dot powder.

[0012] An aqueous solution containing acetylacetone, ammonium acetate, glacial acetic acid, ethanol, and blue fluorescent carbon powder is injected into an ink cartridge, and the aqueous solution is inkjet printed onto cellulose paper to obtain the ratio fluorescent test paper.

[0013] In some embodiments of the present invention, the volume-to-mass ratio of ethylenediamine to citric acid is 300 μL:1 g - 350 μL:1.5 g, and more preferably, the volume-to-mass ratio of ethylenediamine to citric acid is 335 μL:1.0507 g.

[0014] In some embodiments of the present invention, the aqueous solution contains acetylacetone at a volume concentration of 15-25%, ammonium acetate at a concentration of 0.1-0.2 g / mL, glacial acetic acid at a volume concentration of 0.1-1%, ethanol at a volume concentration of 15-25%, and blue fluorescent carbon dot powder at a concentration of 0.05-0.1 g / mL.

[0015] In some embodiments of the present invention, the aqueous solution contains acetylacetone at a volume concentration of 20.7%, ammonium acetate at a concentration of 0.12 g / mL, glacial acetic acid at a volume concentration of 0.4%, ethanol at a volume concentration of 20%, and blue fluorescent carbon dot powder at a concentration of 0.08 g / mL.

[0016] Secondly, embodiments of the present invention provide a ratio fluorescent test strip capable of real-time detection of formaldehyde exposure, prepared by the above-described method.

[0017] Thirdly, embodiments of the present invention provide a method for detecting formaldehyde exposure, based on the aforementioned ratio fluorescent test paper, comprising the following steps:

[0018] Expose the ratio fluorescent test strip to the gas to be tested and let it stand for 30-40 minutes;

[0019] Observe the color of the ratio fluorescent test strip and compare it with the standard colorimetric card to determine the formaldehyde content in the gas to be tested; or, take a picture of the ratio fluorescent test strip with a camera, use color selection software to extract and analyze the RGB signal of the picture, and then compare it with the RGB signal of the standard colorimetric card to determine the formaldehyde content in the gas to be tested.

[0020] Fourthly, embodiments of the present invention provide an application of a ratiometric fluorescent test strip capable of real-time detection of formaldehyde exposure, comprising fixing the ratiometric fluorescent test strip to a wearable device for detecting formaldehyde exposure in the environment. The formaldehyde exposure includes cumulative formaldehyde exposure and real-time formaldehyde exposure.

[0021] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0022] The ratiometric fluorescent test strip provided by this invention achieves efficient, sensitive, and visual on-site detection of formaldehyde based on the solid-phase fluorescence internal filtration effect and the Hantzsch reaction. The Hantzsch reaction of formaldehyde utilizes a mixture of acetylacetone and ammonium salts to react with formaldehyde to generate a pale yellow, green-fluorescent dihydropyridine derivative. Introducing blue fluorescent carbon dots (CDs) into the system under this characteristic reaction effectively overlaps their fluorescence spectrum with the absorption spectrum of the characteristic colorimetric product of formaldehyde, thus constructing a fluorescence sensor based on the solid-phase fluorescence internal filtration effect (SPFFE) and simultaneously forming a ratiometric fluorescent sensor whose fluorescence changes from blue to green.

[0023] The preparation method provided by this invention loads a ratiometric fluorescent mixed material onto cellulose test paper via inkjet printing to form formaldehyde test paper. By detecting changes in fluorescence color, a simple and sensitive on-site detection of formaldehyde content in complex matrix samples can be achieved (detection limit is 0.03 mg / L), without the need for a complicated and cumbersome sample pretreatment process.

[0024] When using the ratio fluorescent test strip provided by this invention, simply place the formaldehyde test strip at the test location for 30 minutes. Without the need for gas collection and enrichment, it can achieve sensitive, low-cost, and visual detection and alarm of the acute toxicity concentration of indoor formaldehyde gas (detection limit is 0.01 ppmv).

[0025] The ratio fluorescence test strip provided by this invention is designed as a wearable sensor. When worn on clothing, it can monitor the cumulative dose of formaldehyde in the human body in real time within a day, and assess the formaldehyde exposure of workers in specific places (such as decorators, hairdressers, factory workers, etc.), thereby providing better protection. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram illustrating the reaction principle of the formaldehyde ratio fluorescent test paper according to an embodiment of the present invention.

[0028] Figure 2 The diagram shows the formaldehyde ratio fluorescent test paper pasting for test example 3. (a) is a schematic diagram of the test paper pasting, and the test paper in the figure is the formaldehyde ratio fluorescent test paper. (b) is a schematic diagram of the changes in the test paper before and after formaldehyde exposure.

[0029] Figure 3 This is a schematic diagram of the on-site analysis steps of the formaldehyde solution in Test Example 1;

[0030] Figure 4 Fluorescent photographs of ratio fluorescent test strips at different formaldehyde concentrations in Test Example 1;

[0031] Figure 5 This is a standard curve obtained at different formaldehyde concentrations in Test Example 1;

[0032] Figure 6 Fluorescent photographs of ratio fluorescent test strips at different formaldehyde concentrations in Test Example 2;

[0033] Figure 7 This is a standard curve obtained at different formaldehyde concentrations in Test Example 2;

[0034] Figure 8 Fluorescent photographs of ratio fluorescent test strips at different formaldehyde concentrations in Test Example 3;

[0035] Figure 9 This is a standard curve obtained at different formaldehyde concentrations in Test Example 3. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0038] Example 1

[0039] Reagents and their preparation: Ethylenediamine, acetylacetone, ammonium acetate, glacial acetic acid, and ethanol were purchased from Chengdu Kelon Chemical Co., Ltd. (Chengdu, China); citric acid was purchased from Aladdin Biochemical Technology Co., Ltd. (Shanghai, China).

[0040] Synthesis of blue fluorescent carbon dot powder (CDs): 335 μL of ethylenediamine and 1.0507 g of citric acid were dissolved in 5 mL of ultrapure water. The solution was then transferred to a 10 mL autoclave lined with Teflon and heated at 200 °C for 5 h. The resulting product was brownish-black and purified by silica gel column chromatography (ultrapure water as eluent, 400-mesh silica gel as stationary phase). After lyophilization, CDs powder was obtained and stored at 4 °C for later use.

[0041] Preparation of formaldehyde ratio fluorescent test strips: Rinse commercial ink cartridges with ultrapure water until all ink is removed, and dry in a 70°C oven for 3 hours. Then, inject an aqueous solution containing acetylacetone (20.7%, v / v), ammonium acetate (0.12 g / mL), glacial acetic acid (0.4%, v / v), ethanol (20%, v / v), and CDs (0.08 g / L) into an empty cartridge. Print the mixed solution onto cellulose paper using a computer-connected inkjet printer. Cut the printed test strips into circular formaldehyde ratio fluorescent test strips approximately 1.5 cm in diameter using a circular embossing tool (Carreboiler), then store them in a sealed, opaque plastic bag away from light in a 4°C refrigerator for later use. The color-changing principle of the formaldehyde ratio fluorescent test strip upon contact with formaldehyde is as follows: Figure 1 As shown.

[0042] Test Example 1

[0043] Formaldehyde solution analysis methods and determination:

[0044] As attached Figure 3As shown, place the formaldehyde ratio fluorescent test strip into the corresponding headspace vial cap, add 10 mL of formaldehyde standard solution (formaldehyde concentrations of 0, 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 5, 7, 9, 12, 15, 17.5, and 20 mg / L), and then seal the headspace vial with the cap. Place the headspace vial in a 50 ℃ constant temperature metal bath and heat for 30 minutes to allow the formaldehyde to fully volatilize and concentrate on the test strip. Then cool for 2 minutes. Transfer the test strip to a fluorescent reading device, visually measure the formaldehyde content under 365 nm UV light, and take a picture. Figure 4 As shown, Figure 4 In this context, FA(l) mg / L refers to the concentration of liquid formaldehyde, expressed in mg / L. Finally, color selection software was used to extract and analyze the RGB signals of the image, yielding the relationship between the G / B value and formaldehyde concentration, and a standard curve was created, as shown below. Figure 5 As shown, the horizontal axis represents the formaldehyde concentration, i.e. Figure 5 The concentration in the figure is expressed in mg / L, and the vertical axis represents the G / B value. In the figure, LOD refers to the limit of detection, which is obtained by dividing the standard deviation of 3 times 11 blank solutions by the slope of the standard curve according to the definition of limit of detection (LOD).

[0045] Test Example 2

[0046] Place the formaldehyde ratio fluorescent test strip in an atmosphere of formaldehyde gas to be tested, where the formaldehyde concentration in the gas is 0, 0.08, 0.16, 0.4, 0.8, 1.2, 1.6, 2.4, 4, 6, or 8 ppmv. Let it stand for 30 minutes to allow the test strip surface to fully contact and react with the formaldehyde in the air. Then transfer the test strip to a fluorescent reading device, visually measure the average concentration of the formaldehyde gas under 365 nm UV light, and take a photograph, as shown in the attached image. Figure 6 As shown, Figure 6 In this context, FA(g)ppmv refers to the concentration of liquid formaldehyde, expressed in ppmv. All images were captured using the same photographic parameters to maintain consistency. Finally, color selection software was used to extract and analyze the RGB signals of the images, yielding the relationship between G / B values ​​and formaldehyde concentration, resulting in a standard curve, as shown in the attached figure. Figure 7 As shown, the horizontal axis represents formaldehyde concentration, i.e. Figure 7 The Concentration value in the graph is expressed in ppmv, and the vertical axis represents the G / B ratio. Figure 7 In this context, LOD refers to the limit of detection, which is calculated by dividing the standard deviation of 3 times the standard deviation of 11 blank solutions by the slope of the standard curve, according to the definition of LOD. The limit of detection is 0.01 ppmv.

[0047] Test Example 3

[0048] As attached Figure 2 As shown, (a) is a schematic diagram of the test strip attachment, where the test strip is a formaldehyde ratio fluorescent test strip; (b) is a schematic diagram of the changes in the test strip before and after formaldehyde exposure. The wearable sensor patch for detecting formaldehyde consists of a reference area and an active area. The active area consists of formaldehyde ratio fluorescent test strips, which are fixed to the surface of black tape with double-sided tape. For the reference area, the prepared formaldehyde ratio fluorescent test strip is first placed in a 0.08 ppmv formaldehyde standard gas atmosphere for 30 minutes, then fixed to the reference area of ​​the black tape with double-sided tape, and finally the surface of the test strip is sealed with transparent tape. Wearable formaldehyde sensor patches were worn on the surface of clothing and exposed to a formaldehyde gas environment. The cumulative exposure doses of formaldehyde gas were 0, 0.8, 1.6, 2.4, 3.2, 4, 5.6, 8, 11.2, 15.2, 20, 25.6, 32, and 41.6 ppmv·min. After 30 minutes, images were taken, and the RGB signals of the images were extracted and analyzed using color selection software. By monitoring changes in fluorescence signals, the cumulative exposure dose was analyzed. The results are as follows: Figure 8 and 9 As shown, Figure 8 For the photos taken, Figure 9 This is a standard curve graph, with the horizontal axis representing the cumulative exposure dose of formaldehyde gas and the vertical axis representing the G / B ratio. The limit of detection (LOD) is 0.64 ppmv·min. Figure 8 In this context, FA dose(g)ppmv.min refers to the exposure amount of gaseous formaldehyde, expressed in ppmv.min. Figure 9 In the figure, the horizontal axis, dose (ppmv.min), refers to the formaldehyde exposure level.

[0049] Test Example 4

[0050] Using commercially available toothpaste and shampoo as test subjects, conduct the tests according to the following steps.

[0051] Method 1: Accurately weigh 0.5 g of sample into a 25 mL headspace vial, add sodium sulfate solution (125 g / L) to a final volume of 25 mL, shake, and incubate at 40 ℃ for 1 h. Rapidly cool the sample solution, and filter the supernatant through a 0.45 μM syringe filter to remove insoluble matter. Perform the detection method according to Example 1.

[0052] Method 2: The test was performed using the acetylacetone spectrophotometric method. The results are shown in Table 1. In Table 1, the amount added refers to the percentage of formaldehyde added to the total sample mass.

[0053] Table 1

[0054]

[0055] Table 1 shows that the formaldehyde content in commercially available toothpaste and shampoo was determined (oral hygiene products ≤ 0.1%, other cosmetics ≤ 0.2%). This study simultaneously analyzed two cosmetic samples using a ratiometric fluorescent test strip method based on the solid-phase fluorescence internal filtration effect and the formaldehyde content determination method in cosmetics as specified in the Ministry of Health of the People's Republic of China's Cosmetic Hygiene Standard. This method is simpler than the national standard method, requiring only simple heating and filtration sample pretreatment. The analytical results are summarized in the table. Formaldehyde was not detected in either of the two commercially available cosmetics. The spiked recoveries of all samples were between 106% and 117%, and the analytical results showed no significant difference compared to the national standard method, indicating that this method can be used for the accurate determination of formaldehyde content in cosmetics.

[0056] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a ratiometric fluorescent test strip capable of real-time detection of formaldehyde exposure, characterized in that, Includes the following steps: An aqueous solution containing acetylacetone, ammonium acetate, glacial acetic acid, ethanol, and blue fluorescent carbon dot powder is injected into an ink cartridge, and the aqueous solution is inkjet printed onto cellulose paper to obtain the ratio fluorescent test paper. In the aqueous solution, the volume concentration of acetylacetone is 20.7%, the concentration of ammonium acetate is 0.12 g / mL, the volume concentration of glacial acetic acid is 0.4%, the volume concentration of ethanol is 20%, and the concentration of blue fluorescent carbon dot powder is 0.08 g / mL.

2. A ratiometric fluorescent test strip capable of real-time detection of formaldehyde exposure, characterized in that, It is prepared by the preparation method described in claim 1.

3. A method for testing formaldehyde exposure, characterized in that, The ratiometric fluorescent test strip prepared based on the method of claim 1 includes the following steps: Expose the ratio fluorescent test strip to the gas to be tested and let it stand for 30-40 minutes; Observe the color of the ratio fluorescent test paper and compare it with the standard color chart to determine the formaldehyde content in the gas to be tested; Alternatively, a photograph can be taken of the ratio fluorescent test strip using a photographic device, and the RGB signal of the photograph can be extracted and analyzed using color selection software. The result can then be compared with the RGB signal of a standard colorimetric card to determine the formaldehyde content in the gas being tested.

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