A test paper for detecting perfluoroisobutyl nitrile, a preparation method and a detection method thereof

Abstract

In order to solve the problem that the power field perfluoroisobutyl nitrile leakage cannot be detected quickly in the prior art, the application provides a test paper for perfluoroisobutyl nitrile detection, a preparation method and a detection method thereof, the test paper for perfluoroisobutyl nitrile detection comprises a substrate and an indicator loaded on the substrate, the structural formula of the indicator is shown as formula 1; R-MgBr, formula 1; wherein R is selected from a fluorescent chromophore group.

Description

Technical Field

[0001] This invention belongs to the field of gas detection, specifically relating to a test strip for the detection of perfluoroisobutyronitrile (PFOS) and its preparation and detection methods. Background Technology

[0002] Perfluoroisobutyronitrile (C4F7N), as a novel environmentally friendly insulating and arc-quenching gas to replace the potent greenhouse gas sulfur hexafluoride, has been gradually applied to medium- and high-voltage gas-insulated power equipment. However, the EPDM rubber seals, currently the most widely used seals in power systems, react to C4F7N to some extent. This reaction corrodes the surface of the seals, leading to a risk of gas leakage. Furthermore, given the long operation and maintenance cycles of gas-insulated equipment, other uncertainties may also cause gas leaks. The median lethal concentration (LD50) of C4F7N is 1000-15000 ppm, posing a potential threat to the respiratory system of living organisms.

[0003] Existing methods for detecting perfluoroisobutyronitrile (PFOBN) include traditional gas chromatography and gas chromatography-mass spectrometry (GC-MS), which provide accurate quantification. However, these methods are costly and involve complex procedures, and can only meet laboratory testing needs. They cannot achieve rapid detection of PFOBN leaks in power plants. Summary of the Invention

[0004] To address the problem that existing technologies cannot achieve rapid detection of perfluoroisobutyronitrile (PFOS) leakage at power plant sites, this invention provides a test strip for PFOS detection, along with its preparation and detection methods.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a test strip for the detection of perfluoroisobutyronitrile (PFOBN), comprising a matrix and an indicator loaded on the matrix, wherein the structural formula of the indicator is shown in Formula 1; R-MgBr, Formula 1; wherein R is selected from fluorescent chromophores.

[0006] Optionally, the indicator comprises a compound shown in Formula 2. Equation 2.

[0007] Optionally, the loading of the indicator on the matrix is ​​3-5 mg / cm³. 2 .

[0008] Optionally, a hydrophobic layer is provided on at least one side of the substrate.

[0009] Optionally, the substrate is selected from non-fluorescent filter paper.

[0010] Optionally, the test strip has a minimum detection concentration of 240 nmol / L for perfluoroisobutyronitrile gas.

[0011] Secondly, this application also provides a method for preparing a test strip for the detection of perfluoroisobutyronitrile as described in any of the preceding claims, comprising the following steps: The indicator shown in Formula 1 is dissolved in tetrahydrofuran to obtain an indicator solution; The matrix is ​​immersed in the indicator solution and then dried under vacuum to obtain a test paper for the detection of perfluoroisobutyronitrile.

[0012] Optionally, the molar concentration of the indicator solution is 0.00001-0.5 mol / L.

[0013] Optionally, the drying temperature is 70-100°C.

[0014] Thirdly, this application also provides a detection method, comprising the following steps: The test strip for the detection of perfluoroisobutyronitrile as described in any of the above items is moistened with tetrahydrofuran and then placed in the test environment. When perfluoroisobutyronitrile is present in the test environment, the indicator undergoes an addition reaction with the perfluoroisobutyronitrile, and the test strip produces a recognizable fluorescent color change under ultraviolet light irradiation.

[0015] In this invention, R in Formula 1 is selected from a fluorescent chromophore, meaning that the R group itself has characteristic fluorescence emission properties. After the indicator undergoes an addition reaction with the nitrile group of perfluoroisobutyronitrile, the conjugated structure of the product changes compared to the indicator, resulting in a visually perceptible shift in the fluorescence spectrum. The strong electron-withdrawing effect of the perfluoroalkyl group in perfluoroisobutyronitrile allows the reaction between perfluoroisobutyronitrile and the indicator to be completed instantaneously, achieving rapid and accurate detection and improving detection sensitivity. Other fluorinated gases commonly found in power equipment, such as sulfur hexafluoride, perfluoropropane, and octafluorocyclobutane, do not possess highly electrophilic cyano structures and cannot undergo addition reactions with Grignard reagents, making the test strip highly specific for perfluoroisobutyronitrile. Compared to existing detection equipment, the test strip of this application is low in cost, easy to operate, and can quickly detect perfluoroisobutyronitrile leaks at power sites. Attached Figure Description

[0016] Figure 1 The fluorescence spectra of the indicator solution shown in Formula 2 before and after the addition of perfluoroisobutyronitrile solution are shown. Figure 2 This is the fluorescence spectrum of a solution of the indicator shown in Formula 2 after titration of a perfluoroisobutyronitrile solution; Figure 3 This is a linear curve of titrating a solution of perfluoroisobutyronitrile with the indicator shown in Equation 2; Figure 4This is a fluorescence stability graph of the solution of the indicator shown in Formula 2; Figure 5 This is a schematic diagram showing the detection process before and after adding perfluoroisobutyronitrile solution to the indicator solution shown in Formula 2. Detailed Implementation

[0017] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] This invention provides a test strip for the detection of perfluoroisobutyronitrile (PFOBN), comprising a matrix and an indicator loaded on the matrix, wherein the structural formula of the indicator is shown in Formula 1; R-MgBr, Formula 1; wherein R is selected from fluorescent chromophores.

[0019] In this embodiment, R in Formula 1 is selected from a fluorescent chromophore, meaning that the R group itself has characteristic fluorescence emission properties. After the indicator undergoes an addition reaction with the nitrile group of perfluoroisobutyronitrile, the conjugated structure of the product changes compared to the indicator, resulting in a visually perceptible shift in the fluorescence spectrum. The strong electron-withdrawing effect of the perfluoroalkyl group in perfluoroisobutyronitrile allows the reaction between perfluoroisobutyronitrile and the indicator to be completed instantaneously, achieving rapid and accurate detection and improving detection sensitivity. Other fluorinated gases commonly found in power equipment, such as sulfur hexafluoride, perfluoropropane, and octafluorocyclobutane, do not possess highly electrophilic cyano structures and cannot undergo addition reactions with Grignard reagents, making the test strip highly specific for perfluoroisobutyronitrile. Compared to existing detection equipment, the test strip of this application is low in cost, easy to operate, and can quickly detect perfluoroisobutyronitrile leaks at power sites.

[0020] Specifically, the fluorescent chromophore R is a group with a conjugated π electron system, and the number of carbon atoms is preferably in the range of C10 to C30. The indicator shown in Formula 1 can be prepared by reacting the corresponding bromide with metallic magnesium to obtain a Grignard reagent.

[0021] Furthermore, in actual use, the test strip is moistened with tetrahydrofuran in a storage box under a nitrogen atmosphere before the reagent kit is opened. Its structure can refer to the medical three-in-one or three-chamber bag packaging mode, with an anhydrous tetrahydrofuran pre-filled bag inside, which can be punctured to release directly. After being moistened, the test strip will not be immediately affected by water, oxygen, or carbon dioxide in the air.

[0022] In some embodiments, the indicator comprises a compound shown in Formula 2. Equation 2.

[0023] The solution of the compound shown in Formula 2 is purple under 365 nm ultraviolet light. After reacting with perfluoroisobutyronitrile, the product is blue under ultraviolet light. When the test strip is loaded with the indicator shown in Formula 2, the results can be read without the need for large instruments. Qualitative judgment can be completed by naked-eye comparison under ultraviolet light, achieving rapid and accurate detection.

[0024] It should be noted that the indicator can also be a compound in which R is selected from other fluorescent chromophores.

[0025] In some embodiments, the loading of the indicator on the matrix is ​​3-5 mg / cm³. 2 .

[0026] The indicator loading was tested using the constant weight weighing method. When the loading was less than 3 mg / cm³, the loading was determined. 2 When the indicator molecules per unit area are insufficient, the proportion of molecules that undergo fluorescence change after reacting with low concentrations of perfluoroisobutyronitrile is low, resulting in reduced color contrast. This leads to an increase in the minimum detection concentration and a decrease in sensitivity. Furthermore, when the loading is too low, the test strip response uniformity is poor, and localized blind zones may appear. When the loading exceeds 5 mg / cm², the reaction is more severe. 2 In some cases, the indicator cannot fully participate in the reaction, resulting in waste.

[0027] In this embodiment, the indicator within this range forms a uniform detection area on the substrate surface, resulting in high utilization of active sites, excellent fluorescence contrast, and fast response. The indicator loading on the substrate includes, but is not limited to, 3.0 mg / cm³. 2 3.1 mg / cm 2 3.2 mg / cm 2 3.3 mg / cm 2 3.4 mg / cm 2 3.5 mg / cm 2 3.6 mg / cm 2 3.7 mg / cm 2 3.8 mg / cm 2 3.9 mg / cm 2 4.0 mg / cm 2 4.2 mg / cm 2 4.4 mg / cm 2 4.6 mg / cm 2 4.8 mg / cm 2 5.0 mg / cm 2 .

[0028] In some embodiments, a hydrophobic layer is provided on at least one side of the substrate. Specifically, the substrate is hydrophobically modified to facilitate the loading of indicators. The hydrophobic treatment method can refer to existing disclosed methods, such as impregnation with silane compounds or vapor deposition.

[0029] In some embodiments, the substrate is selected from non-fluorescent filter paper. Specifically, it can be selected from nitrocellulose filter paper or cellulose acetate filter paper. Using non-fluorescent filter paper reduces background fluorescence interference.

[0030] In some embodiments, the test strip has a minimum detectable concentration of 240 nmol / L for perfluoroisobutyronitrile (PFOB) gas. 240 nmol / L translates to a volume concentration of approximately 5.4 ppm under standard conditions, which is far below the median lethal concentration (LD50) of 1000-15000 ppm for PFOB, and also far below the safety threshold for long-term human exposure. This detection limit allows for early warning of gas leaks, enabling detection before the leak concentration reaches levels harmful to humans, thus ensuring worker safety.

[0031] One embodiment of this application also provides a method for preparing a test strip for the detection of perfluoroisobutyronitrile as described in any of the preceding claims, comprising the following steps: The indicator shown in Formula 1 is dissolved in tetrahydrofuran to obtain an indicator solution; The matrix is ​​immersed in the indicator solution and then dried under vacuum to obtain a test paper for the detection of perfluoroisobutyronitrile.

[0032] The preparation method of this embodiment has a short process flow, is simple to operate, requires no complicated equipment, has high production efficiency, and has a high raw material utilization rate, which further reduces the preparation cost of the test strip.

[0033] The preparation process in this embodiment is carried out in an anhydrous and oxygen-free inert atmosphere. Argon or high-purity nitrogen can be used as the inert gas to avoid oxidation, hydrolysis and deactivation of Grignard reagents.

[0034] Furthermore, the specific steps of "immersing the matrix in the indicator solution" include: Place the substrate in a container and add indicator solution dropwise until the substrate is completely submerged.

[0035] In some embodiments, the molar concentration of the indicator solution is 0.00001-0.5 mol / L.

[0036] When the concentration is below 0.00001 mol / L, a single impregnation cannot achieve 3 mg / cm³. 2The minimum loading amount can easily cause uneven response speed and poor sensitivity of the test paper; when the concentration is higher than 0.5 mol / L, the viscosity of the solution increases significantly, and the indicator solution is prone to forming a liquid film on the surface. After drying, the local loading amount of the indicator exceeds the standard, resulting in waste of raw materials.

[0037] By limiting the molar concentration of the indicator solution within the above range, the indicator loading of the test strip can be controlled at 3.0-5.0 mg / cm³. 2 Within the specified range, the process is simple and controllable, with high production efficiency. The molar concentration of the indicator solution includes, but is not limited to, 0.0001 mol / L, 0.001 mol / L, 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L.

[0038] In some embodiments, the drying temperature is 70-100°C.

[0039] When the temperature is below 70℃, the volatilization rate of tetrahydrofuran in a vacuum environment is too slow, reducing production efficiency. When the temperature is above 100℃, the thermal stability of Grignard reagent decreases, which alters the structure of the fluorescent group. At the same time, high temperatures cause the filter paper fibers to shrink and become brittle, making the final test paper easily damaged and difficult to store.

[0040] By limiting the drying temperature within the above range, the solvent evaporation rate is moderate, ensuring the structural stability of the indicator while maintaining the performance of the matrix; the drying temperature includes, but is not limited to, 70℃, 73℃, 75℃, 77℃, 80℃, 82℃, 84℃, 85℃, 86℃, 88℃, 90℃, 92℃, 94℃, 95℃, 97℃, and 100℃.

[0041] An embodiment of this application also provides a detection method, including the following steps: The test strip for the detection of perfluoroisobutyronitrile as described in any of the above items is moistened with tetrahydrofuran and then placed in the test environment. When perfluoroisobutyronitrile is present in the test environment, the indicator undergoes an addition reaction with the perfluoroisobutyronitrile, and the test strip produces a recognizable fluorescent color change under ultraviolet light irradiation.

[0042] Compared to existing detection methods that cannot be adapted to rapid on-site troubleshooting in power facilities, the detection method in this embodiment does not require large instruments; it can be operated with just a portable ultraviolet lamp. It has a short response time and can quickly and systematically check equipment seals, flanges, and other locations to accurately pinpoint leaks. Furthermore, this detection method is based on a specific chemical reaction, unaffected by interference from other coexisting gases, resulting in highly reliable test results. The test strips can be stored for a long time and are ready for use simply by wetting them on-site; they are freshly prepared and used immediately, making them suitable for various scenarios such as regular inspections and sudden leak detection.

[0043] The present invention will be further illustrated by the following examples.

[0044] Example 1 Dissolve 20 mg of the indicator TPA-MgBr in 5 mL of THF. Lay non-fluorescent filter paper flat in a glass petri dish, and add 1 mL of the THF solution containing the indicator to completely submerge it. Then transfer the petri dish to an oven and dry at 80°C to obtain the TPA-MgBr test strip. The indicator loading is 4 mg / cm³. 2 .

[0045] After wetting the test strip with 0.3 mL of THF, the test strip is immersed in an atmosphere of perfluoroisobutyronitrile containing 10% C4F7N and 90% CO2. It can be observed that under 365 nm ultraviolet irradiation in the perfluoroisobutyronitrile atmosphere, the test strip quickly changes from purple to blue, achieving visual detection. This can be used for the precise location of leaks in perfluoroisobutyronitrile pipelines.

[0046] Example 2 Example 2 is essentially the same as Example 1, except that non-fluorescent filter paper is laid flat in a glass petri dish, and 0.75 mL of THF solution containing the indicator is added, with an indicator loading of 3 mg / cm³. 2 .

[0047] In a perfluoroisobutyronitrile atmosphere, under 365nm ultraviolet irradiation, the test paper rapidly changes from purple to blue.

[0048] Example 3 Example 3 is essentially the same as Example 1, except that non-fluorescent filter paper is laid flat in a glass petri dish, and 0.5 mL of THF solution containing the indicator is added, with an indicator loading of 2 mg / cm³. 2 .

[0049] In a perfluoroisobutyronitrile atmosphere, under 365nm ultraviolet irradiation, the test paper rapidly changes from purple to blue-purple.

[0050] Example 4 Example 4 is essentially the same as Example 1, except that non-fluorescent filter paper is laid flat in a glass petri dish, and 1.25 mL of THF solution containing the indicator is added, with an indicator loading of 5 mg / cm³. 2 .

[0051] In a perfluoroisobutyronitrile atmosphere, under 365nm ultraviolet irradiation, the test paper rapidly changes from purple to blue.

[0052] Example 5 Example 5 is essentially the same as Example 1, except that non-fluorescent filter paper is laid flat in a glass petri dish, and 2 mL of THF solution containing the indicator is added. The indicator loading is 8 mg / cm³. 2 .

[0053] In a perfluoroisobutyronitrile atmosphere, under 365nm ultraviolet irradiation, the test paper rapidly changes from purple to blue.

[0054] Test case 1 g of 4-bromotriphenylamine (TPA-Br) and 1 g of Mg powder were added to a 50 mL single-necked flask, followed by the addition of anhydrous tetrahydrofuran (THF) and refluxed for 12 h. After reflux, the reaction solution was filtered under a nitrogen atmosphere to remove the Mg powder. The solid obtained by rotary evaporation of the filtrate was dried in a vacuum drying oven. The dried powder was stored under nitrogen for later use; this powder is the indicator TPA-MgBr of Formula 2. 1.735 mg of TPA-Br was dissolved in 5 mL of THF to prepare a 1×10⁻⁶ solution. -3 The mother liquor was diluted 1000 times to prepare the detection working solution.

[0055] Add 1×10⁻⁶ of perfluoroisobutyronitrile to 2 mL of working solution. -3 Fluorescence detection was performed using a mol / L THF solution. Figure 1 and Figure 2 The results shown in the figure indicate that as the amount of perfluoroisobutyronitrile (PFIR) increases, the fluorescence intensity at 400 nm gradually decreases, while the fluorescence intensity at 600 nm gradually increases. This result directly proves that the indicator and PFIR have undergone a characteristic chemical reaction, the molecular conjugated structure and electron cloud distribution have changed, and the fluorescence spectral characteristics have produced significant differences, providing a signal basis for the fluorescence detection of PFIR.

[0056] Depend on Figure 2 It can be seen that as the concentration of perfluoroisobutyronitrile (PFOBN) gradually increases from 0 μM to 35 μM, the characteristic fluorescence emission intensity of the indicator in Formula 2 near 400 nm shows a gradient decreasing trend. Meanwhile, the fluorescence signal at 600 nm gradually increases with increasing PFOBN concentration.

[0057] Depend on Figure 3 It can be seen that within the concentration range of 0-35 μM, the fluorescence intensity of the indicator in Formula 2 exhibits a good linear negative correlation with the concentration of perfluoroisobutyronitrile (PFOBN). The linear fitting equation is Y = -1.21X + 94.15, with a linear correlation coefficient R² of 0.98899, demonstrating excellent linearity. Based on the 3σ / K method, the limit of detection (LOD) for PFOBN of this detection system is calculated to be 0.24 μM (i.e., 240 nmol / L). This result verifies that the indicator possesses high-sensitivity quantitative detection capability, enabling accurate detection of low concentrations of PFOBN.

[0058] Depend on Figure 4 As can be seen, the indicator solution shown in Formula 2 exhibits only a slight decrease in characteristic fluorescence intensity during the 8-hour observation period, with the overall fluorescence intensity consistently remaining above 80% of its initial value, without significant fluorescence quenching or performance degradation. This result demonstrates that the indicator possesses excellent fluorescence stability, with stable molecular structure and optical properties within the detection window, ensuring the reliability and repeatability of detection results and meeting the needs of long-term on-site investigations.

[0059] Depend on Figure 5 It is evident that the solution of the indicator in Formula 2 exhibits purple fluorescence under ultraviolet light before the introduction of perfluoroisobutyronitrile (PFOBN), and blue fluorescence under ultraviolet light after the introduction of PFOBN. The color difference is significant and clearly distinguishable to the naked eye. This result directly verifies that the test strip using this indicator can achieve rapid and visual detection of PFOBN through fluorescence color changes, providing results without the need for complex instruments, thus making it suitable for applications involving rapid investigation of power leaks in the field.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A test strip for detecting perfluoroisobutyronitrile (PFOBN), characterized in that, The invention includes a matrix and an indicator loaded on the matrix, the structural formula of which is shown in Formula 1. R-MgBr, Formula 1; wherein R is selected from fluorescent chromophores.

2. The test strip for detecting perfluoroisobutyronitrile according to claim 1, characterized in that, The indicator comprises the compound shown in Formula 2. Equation 2.

3. The test strip for detecting perfluoroisobutyronitrile according to claim 1, characterized in that, The loading of the indicator on the matrix is ​​3-5 mg / cm³. 2 .

4. The test strip for detecting perfluoroisobutyronitrile according to claim 1, characterized in that, A hydrophobic layer is provided on at least one side of the substrate.

5. The test strip for detecting perfluoroisobutyronitrile according to claim 1, characterized in that, The matrix is ​​selected from non-fluorescent filter paper.

6. The test strip for detecting perfluoroisobutyronitrile according to claim 1, characterized in that, The test strip has a minimum detection concentration of 240 nmol / L for perfluoroisobutyronitrile gas.

7. The method for preparing the test strip for detecting perfluoroisobutyronitrile according to any one of claims 1-6, characterized in that, Includes the following steps: The indicator shown in Formula 1 is dissolved in tetrahydrofuran to obtain an indicator solution; The matrix is ​​immersed in the indicator solution and then dried under vacuum to obtain a test paper for the detection of perfluoroisobutyronitrile.

8. The preparation method according to claim 7, characterized in that, The molar concentration of the indicator solution is 0.00001-0.5 mol / L.

9. The preparation method according to claim 7, characterized in that, The drying temperature is 70-100℃.

10. A detection method, characterized in that, Includes the following steps: The test paper for the detection of perfluoroisobutyronitrile according to any one of claims 1-6 is moistened with tetrahydrofuran and then placed in the test environment; When perfluoroisobutyronitrile is present in the test environment, the indicator undergoes an addition reaction with the perfluoroisobutyronitrile, and the test strip produces a recognizable fluorescent color change under ultraviolet light irradiation.

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