High-sensitivity nitrite test paper and preparation method thereof

Abstract

The invention relates to high-sensitivity nitrite detection test paper and a preparation method thereof.The test paper comprises a detection base layer, the detection base layer contains a nitrite ion reaction substrate, the nitrite ion reaction substrate is red after making contact with nitrite ions, different nitrite ion concentrations are distinguished through different color gradations of the color, and the nitrite ion concentration is different from that of the nitrite ion reaction substrate. The detection base layer is soaked in a feed liquid and then is dried to obtain the high-sensitivity nitrite detection test paper, the feed liquid contains a nitrite ion reaction substrate and a pH regulator, and the nitrite ion reaction substrate is selected from one or more of aniline, p-toluidine, aminonaphthalene and Klehu acid. Compared with the prior art, the method provided by the invention has the characteristics of accurate concentration indication and high sensitivity, and especially when the nitrite concentration is low, the color gradation of different concentrations is clear.

Description

Technical Field

[0001] The invention belongs to the technical fields of chemical analysis, water quality testing, environmental testing and food testing, and relates to a high-sensitivity nitrite detection test paper and a preparation method thereof. Background Art

[0002] Microorganisms in water can break down and digest free amines, producing nitrites. Accumulation of nitrites can affect the survival of fish and shrimp. Monitoring nitrite levels in water is essential for aquaculture and pet fish breeding.

[0003] Excessive nitrite levels can also irritate human skin. Therefore, testing the nitrite content in swimming pool water and spa pool water is also of certain practical significance.

[0004] Sodium nitrite can inhibit the growth of harmful bacteria like Clostridium botulinum and is primarily used in food processing to preserve preserved foods. However, nitrite has significant acute toxicity and is carcinogenic. A single intake of 0.2g or more can cause poisoning, and long-term nitrite intake can lead to chronic poisoning and carcinogenesis. Therefore, the amount of nitrite added during preserved food processing and the amount remaining in the final product must be strictly controlled.

[0005] Currently, most nitrite detection products on the market are kits, which are cumbersome to use. Test strips also have low sensitivity, with unclear color differentiation below 1.0 ppm. This is primarily due to the fact that traditional nitrite detection strips use potassium iodide as a reaction substrate, which reacts slowly and produces a lighter-colored reaction product.

[0006] Patent CN118837351A discloses a nitrite detection element and a nitrite detection method, which consists of a paper-based material, a nitrite color developer, a pH regulator, and a product adsorption reagent. Using a commonly used paper-based chip manufacturing method, the paper-based material is cut or blocked by a hydrophobic sealing material to form a long liquid flow channel. The nitrite color developer and product adsorption reagent are modified on the channel. The colored product generated after the color development reaction is adsorbed in the area where the reaction occurs and does not flow with the liquid. After the detection experiment is completed, by observing whether the color development area changes color and the length of the color development area, it can be determined whether the sample contains nitrite and the level of nitrite. The nitrite concentration can be determined by measuring the length of the color development area with an additional ruler or a ruler provided on the chip. However, the use of the components in this patent is relatively complicated.

[0007] Patent CN108139524A discloses a composition for anisotropic pigment film and anisotropic pigment film. The method involves adding sodium nitrite to 3-aminoquinoline and water in the presence of hydrochloric acid for diazotization, followed by coupling with 8-amino-2-naphthalenesulfonic acid (1,7-clefic acid) dissolved in water. However, the reaction time in this patent is long, making it unsuitable for use in nitrite detection test strips.

[0008] Patent CN101413897A discloses a method and kit for detecting a nitrite shielding agent in milk. The nitrite developer can be a liquid developer, prepared by dissolving 1-naphthol, 1-naphthylamine, and anhydrous p-aminobenzenesulfonic acid in water, adding glacial acetic acid, and mixing thoroughly. However, the developer in this patent exhibits slightly low sensitivity when used with nitrite test strips. Summary of the Invention

[0009] The purpose of the present invention is to provide a highly sensitive nitrite detection test paper and a preparation method thereof in order to overcome at least one of the defects of the above-mentioned prior art. The present invention has the characteristics of accurate concentration indication and high sensitivity. Especially when the nitrite concentration is low, the color levels of different concentrations are clear.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] One of the technical solutions of the present invention is to provide a highly sensitive nitrite detection test paper, which includes a detection base layer containing a nitrite ion reaction substrate. The nitrite ion reaction substrate turns red after contact with nitrite ions, and different color levels can clearly distinguish different nitrite ion concentrations.

[0012] The detection substrate is immersed in a liquid and then dried to obtain a high-sensitivity nitrite detection test paper. The nitrite ion reaction substrate is attached to the surface of the detection substrate. The liquid contains the nitrite ion reaction substrate and a pH regulator. The nitrite ion reaction substrate is selected from one or more aromatic amines selected from aniline, p-toluidine, aminonaphthalene, and clevolic acid.

[0013] As a preferred technical solution, the detection base layer is made of filter paper.

[0014] Furthermore, the pH regulator is selected from one or more solid acids selected from citric acid, phthalic acid, and p-toluenesulfonic acid.

[0015] Furthermore, the mass ratio of the nitrite ion reaction substrate to the pH regulator is 1:(1-10), the mass concentration of the nitrite ion reaction substrate in the feed solution is 0.1-1 g / L, and the mass concentration of the pH regulator is 0.1-2 g / L.

[0016] As a preferred technical solution, the mass ratio of the nitrite ion reaction substrate to the pH regulator is 1:(2-5), the mass concentration of the nitrite ion reaction substrate in the feed solution is 0.2-0.5 g / L, and the mass concentration of the pH regulator is 0.5-1 g / L.

[0017] Furthermore, the feed liquid also contains a solvent, and the solvent is selected from one or more of water and ethanol.

[0018] Furthermore, the slurry also contains a reaction developer, which is one or more substances containing phenolic hydroxyl groups selected from β-naphthol and N,N-dimethyl-m-hydroxyaniline. The mass concentration of the reaction developer is 0-0.5 g / L.

[0019] As a preferred technical solution, the mass concentration of the reaction developer is 0.15 to 0.25 g / L.

[0020] Furthermore, the test paper also includes a substrate, one end of the substrate is set as a hand-held area, and the other end is set as a detection area, and the detection base layer is pasted on the detection area.

[0021] As a preferred technical solution, the material of the substrate is selected from polyethylene terephthalate (PET) or polyvinyl chloride (PVC) plastic.

[0022] Furthermore, the method for using the test paper (highly sensitive nitrite detection method) comprises the following steps:

[0023] Immerse the test paper in the test liquid, shake off the excess liquid on the test paper, place the test paper horizontally facing upwards, and compare the reading with the colorimetric card to detect the nitrite ion concentration;

[0024] The preparation method of the colorimetric card comprises the following steps:

[0025] Immerse the test paper in nitrite solutions with different nitrite ion concentrations, shake off the excess liquid on the test paper, place the test paper horizontally with the face upwards, and make a standard colorimetric card with the same color tone according to the color of the test paper;

[0026] The immersion temperature is 10-40°C and the time is 1-20 seconds.

[0027] The placing temperature is 10-40° C. and the time is 10-45 seconds.

[0028] As a preferred technical solution, the nitrite is selected from one or more of sodium nitrite and potassium nitrite, and the solvent of the nitrite solution is water.

[0029] The nitrite ion concentration detected by the test paper is 0.1 to 10.0 mg / L (ppm).

[0030] One of the technical solutions of the present invention is to provide a method for preparing the highly sensitive nitrite detection test paper, the method comprising the following steps:

[0031] The raw materials are mixed to form a liquid, the detection substrate is completely immersed in the liquid, and the liquid is dried at low temperature and reduced pressure to obtain a high-sensitivity nitrite detection test paper.

[0032] Furthermore, the immersion temperature is 10-40° C., and the immersion time is 5-30 seconds.

[0033] Furthermore, the temperature of the low-temperature reduced-pressure drying is 25 to 50° C., the vacuum degree is 0.1 to 20 Pa, and the time is 40 to 120 min.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention transforms the chemical titration method into a test paper method, which does not require a specific environment and professional operating skills, can achieve rapid detection of nitrite content, and is easy to use; the amount of test reagent used is less than that used in laboratory methods, saving testing costs; the test paper substrate includes a handheld area, which enables the operator to avoid reagent contamination when taking the test paper and testing, and is widely applicable to industries such as chemical analysis, water quality testing, environmental testing, food testing, and various water quality testing scenarios in daily use;

[0036] (2) The production process of the present invention is reasonable, the raw materials used are easy to obtain, the equipment cost is low, and batch production can be carried out;

[0037] (3) The present invention has the characteristics of accurate concentration indication, high sensitivity, simple operation, fast testing speed, non-toxic test paper to the human body, and high safety. Especially when the nitrite concentration is low, the color scale of different concentrations is clear;

[0038] (4) The reaction substrate of the present invention can react with nitrite ions simultaneously with the reaction color developer to generate a complex having a color different from that of the reaction substrate, thereby indicating the concentration of nitrite ions. The color difference varies greatly with the concentration, which is convenient for reading. The pH regulator adjusts the acidity and alkalinity so that the reaction is within the appropriate pH range. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the structure of a high-sensitivity nitrite detection test paper in an embodiment of the present invention;

[0040] Figure 2 Graph showing the relationship between the color of the standard colorimetric card and the nitrite ion concentration in an embodiment of the present invention.

[0041] Description of the marks in the figure:

[0042] 1—Detection area, 2—Substrate, 3—Handheld area. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0044] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0045] Example 1:

[0046] A highly sensitive nitrite test paper, such as Figure 1 As shown, it includes a detection base layer and a substrate 2. One end of the substrate 2 is set as a hand-held area 3, and the other end is set as a detection area 1. The detection area 1 is pasted with a detection base layer, and the detection base layer contains a nitrite ion reaction substrate. The nitrite ion reaction substrate turns red after contacting nitrite ions, and different color levels can clearly distinguish different nitrite ion concentrations.

[0047] The preparation method of the above-mentioned highly sensitive nitrite detection test paper comprises the following specific steps:

[0048] S1.1. Weigh 0.05 g of cleavage acid and 0.1 g of p-toluenesulfonic acid, add 100 mL of pure water, and stir at 25°C until all the solids are dissolved to obtain a feed solution. Completely immerse chromatography-grade filter paper in the feed solution at 25°C. After 10 seconds, remove the filter paper and place it in an oven at 40°C and a vacuum degree of 10 Pa for 80 minutes. The nitrite ion reaction substrate adheres to the surface of the detection substrate, and a detection substrate that meets the requirements is obtained.

[0049] S1.2. Cut the detection substrate into strips of 0.5 cm × 20 cm, stick them on one side of the polyvinyl chloride (PVC) substrate 2, and then cut them in units of 0.5 cm width. The final detection substrate size is 0.5 cm × 0.5 cm, and a high-sensitivity nitrite detection test paper is obtained.

[0050] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity nitrite detection test paper comprises the following specific steps:

[0051] S2.1, prepare nitrite ion standard solutions of different concentrations using sodium nitrite and pure water at 25°C.

[0052] Weigh 0.14 g of sodium nitrite into a 1000 mL volumetric flask, add 200 mL of pure water to dissolve it, then dilute to the mark with pure water and mix thoroughly to obtain a 100 mg / L (ppm) nitrite ion standard stock solution.

[0053] Pipette 10.0 mL of 100 mg / L nitrite ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 10.0 mg / L (ppm) nitrite ion standard solution.

[0054] Pipette 5.0 mL of 100 mg / L nitrite ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 5.0 mg / L (ppm) nitrite ion standard solution.

[0055] Pipette 2.0 mL of 100 mg / L nitrite ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 2.0 mg / L (ppm) nitrite ion standard solution.

[0056] Pipette 1.0 mL of 100 mg / L nitrite ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 1.0 mg / L (ppm) nitrite ion standard solution.

[0057] Pipette 8.0 mL of 10.0 mg / L nitrite ion standard solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 0.8 mg / L (ppm) nitrite ion standard solution.

[0058] Pipette 4.0 mL of 10.0 mg / L nitrite ion standard solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 0.4 mg / L (ppm) nitrite ion standard solution.

[0059] Pipette 2.0 mL of 10.0 mg / L nitrite ion standard solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 0.2 mg / L (ppm) nitrite ion standard solution.

[0060] Pipette 1.0 mL of 10.0 mg / L nitrite ion standard solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 0.1 mg / L (ppm) nitrite ion standard solution.

[0061] S2.2. Immerse the test paper in nitrite ion standard solutions with different nitrite ion concentrations at 25°C. After 5 seconds, remove the test paper and shake off the excess solution on the test paper. Place the test paper horizontally upward at 25°C for 30 seconds. Figure 2 As shown in the figure, a standard color chart with consistent hues was made using Adobe Illustrator CS6 software.

[0062] When the nitrite ion concentration is 0.1-10.0 mg / L, the color levels of different concentrations are clear.

[0063] The highly sensitive nitrite test paper is subjected to the following test or experiment, and the test or experiment results are then analyzed.

[0064] Test Example 1:

[0065] The anti-interference test of the above-mentioned high-sensitivity nitrite detection test paper is carried out as follows:

[0066] Prepare 100 mg / L (ppm) sodium chloride solution, sodium carbonate solution, sodium bicarbonate solution, magnesium sulfate solution, sodium sulfite solution, potassium nitrate solution, potassium dihydrogen phosphate solution, and dipotassium hydrogen phosphate solution, respectively, and mix the prepared solutions with 10.0 mg / L nitrite ion standard solution at a volume ratio of 1:1 to obtain interference group solutions;

[0067] Immerse the test paper in the interference group solution at 25°C, take out the test paper after 5 seconds, shake off the excess liquid on the test paper, place the test paper horizontally upward at 25°C for 30 seconds, and compare the reading with the standard colorimetric card to detect the nitrite ion concentration.

[0068] The test paper in this embodiment was used for anti-interference testing of interference group solutions of chloride ions, carbonate ions, bicarbonate ions, sulfate ions, sulfite ions, nitrate ions, dihydrogen phosphate ions and hydrogen phosphate ions. It was found that the test paper could still develop color normally under the interference group, and the test paper was not affected by chloride ions, carbonate ions, bicarbonate ions, sulfate ions, sulfite ions, nitrate ions, dihydrogen phosphate ions and hydrogen phosphate ions.

[0069] Test Example 2:

[0070] The detection upper limit test of the above-mentioned high-sensitivity nitrite test paper is carried out as follows:

[0071] Referring to the preparation of nitrite ion standard solution, 100 mg / L nitrite ion standard stock solution was used to prepare nitrite ion solutions of 20.0 mg / L (ppm), 30.0 mg / L (ppm), 40.0 mg / L (ppm), and 50.0 mg / L (ppm);

[0072] Immerse the test paper in nitrite ion solution at 25℃, take out the test paper after 5s, shake off the excess liquid on the test paper, place the test paper horizontally upward at 25℃ for 30s, and compare the reading with the standard colorimetric card to detect the nitrite ion concentration.

[0073] The test paper in this embodiment was used to test the upper limit of detection of nitrite ion solutions of different concentrations. It was found that the test paper showed a dark red color in a 20.0 mg / L nitrite ion solution, which was basically consistent with the color of a 10.0 mg / L nitrite ion solution. For nitrite ion solutions above 30.0 mg / L, the test paper's color became lighter instead; that is, the upper limit of detection of the test paper was 10.0 mg / L.

[0074] Test Example 3:

[0075] The detection limit test of the above-mentioned high-sensitivity nitrite test paper is carried out as follows:

[0076] Referring to the preparation of nitrite ion standard solution, 10.0 mg / L nitrite ion standard solution was used to prepare 0.01 mg / L (ppm), 0.02 mg / L (ppm), and 0.05 mg / L (ppm) nitrite ion solutions respectively;

[0077] Immerse the test paper in nitrite ion solution at 25℃, take out the test paper after 5s, shake off the excess liquid on the test paper, place the test paper horizontally upward at 25℃ for 30s, and compare the reading with the standard colorimetric card to detect the nitrite ion concentration.

[0078] The test paper in this embodiment was used to test the lower limit of detection of nitrite ion solutions of different concentrations. It was found that the test paper did not change color for nitrite ion solutions below 0.05 mg / L, that is, the lower limit of detection of the test paper was 0.1 mg / L.

[0079] Example 2:

[0080] A high-sensitivity nitrite detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.02 g of cleavage acid and 0.1 g of p-toluenesulfonic acid are weighed.

[0081] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity nitrite detection test paper is the same as that in Example 1.

[0082] The test paper in Example 2 was used for testing. Compared with Example 1, the color of the test paper became lighter, the distinction was not as obvious as in Example 1, and the lower limit of detection became 0.8 mg / L, the upper limit remained 10.0 mg / L, the detection limit range was narrowed, and the sensitivity decreased, reflecting that the reduction in the concentration of the nitrite ion reaction substrate will affect the detection limit range and sensitivity. The anti-interference ability is basically the same as that in Example 1.

[0083] Example 3:

[0084] A highly sensitive nitrite detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.02 g of p-toluidine and 0.02 g of N,N-dimethyl-m-hydroxyaniline are weighed, 50 mL of ethanol is first added, and the mixture is stirred at 25° C. until the solid is completely dissolved, and then 0.1 g of p-toluenesulfonic acid and 50 mL of pure water are added, and the mixture is stirred at 25° C. until the solid is completely dissolved to obtain a feed solution.

[0085] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity nitrite detection test paper is the same as that in Example 1.

[0086] The test paper in Example 3 was used for testing. Compared with Example 1, the color of the test paper became lighter, the distinction was not as obvious as in Example 1, and the lower limit of detection became 1.0 mg / L, and the upper limit remained 10.0 mg / L. The detection limit range was narrowed and the sensitivity decreased, reflecting that even if a reaction developer was added, the replacement of the nitrite ion reaction substrate would affect the detection limit range and sensitivity. The anti-interference ability was basically the same as that in Example 1.

[0087] Comparative Example 1:

[0088] A highly sensitive nitrite detection test paper and a preparation method thereof are basically the same as those in Example 1, except that in step S1.1, 0.02 g of N,N-dimethyl-m-hydroxyaniline is weighed, 50 mL of ethanol is added, and the mixture is stirred at 25° C. until the solid is completely dissolved, and then 0.02 g of p-aminobenzenesulfonic acid, 0.1 g of p-toluenesulfonic acid, and 50 mL of pure water are added, and the mixture is stirred at 25° C. until the solid is completely dissolved to obtain a feed solution.

[0089] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity nitrite detection test paper is the same as that in Example 1.

[0090] The test paper in Comparative Example 1 was used for testing. Compared with Example 3, the test paper showed white color at all concentrations of nitrite ion solution, and the test paper could not be used.

[0091] Comparative Example 2:

[0092] A highly sensitive nitrite detection test paper and a preparation method thereof are basically the same as Example 1, except that in step S1.1, 0.02 g of p-aminobenzenesulfonic acid and 0.05 g of p-toluenesulfonic acid are weighed, 50 mL of pure water are first added, and the mixture is stirred at 25°C until the solid is completely dissolved. Then, 0.01 g of β-naphthol is added to 50 mL of ethanol, and the mixture is stirred at 25°C until the solid is completely dissolved. Then, the two parts of liquid are evenly mixed to obtain a feed liquid.

[0093] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity nitrite detection test paper is the same as that in Example 1.

[0094] The test paper in Comparative Example 2 was used for testing. Compared with Example 3, the color of the test paper became lighter, the distinction was not as obvious as in Example 3, and the lower limit of detection became 5.0 mg / L, while the upper limit remained at 10.0 mg / L. The detection limit range was significantly narrowed, the sensitivity was significantly reduced, and the test paper was difficult to use.

[0095] When p-aminobenzenesulfonic acid is used as the reaction substrate for nitrite ions, even if a reaction color developer is added, the sensitivity of the test paper reaction is low, because the reaction between p-aminobenzenesulfonic acid and nitrite requires a strong acid, and the reaction between the reaction color developer and the intermediate generated by the reaction of p-aminobenzenesulfonic acid and nitrite requires a neutral environment for color development. Therefore, the test paper is almost unusable.

[0096] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A highly sensitive nitrite detection test paper, characterized in that, The test paper comprises a detection base layer, which contains a nitrite ion reaction substrate. The nitrite ion reaction substrate turns red after contacting with nitrite ions, and different color levels distinguish different nitrite ion concentrations. The detection substrate is immersed in a liquid and then dried to obtain a high-sensitivity nitrite detection test paper. The liquid contains a nitrite ion reaction substrate and a pH regulator. The nitrite ion reaction substrate is selected from one or more of aniline, p-toluidine, aminonaphthalene, and clevolic acid.

2. a highly sensitive nitrite detection test paper according to claim 1, is characterized in that, The pH regulator is selected from one or more of citric acid, phthalic acid, and p-toluenesulfonic acid.

3. a highly sensitive nitrite detection test paper according to claim 1, is characterized in that, The mass ratio of the nitrite ion reaction substrate to the pH regulator is 1:(1-10), the mass concentration of the nitrite ion reaction substrate in the feed solution is 0.1-1 g / L, and the mass concentration of the pH regulator is 0.1-2 g / L.

4. a highly sensitive nitrite detection test paper according to claim 1, is characterized in that, The feed liquid further contains a solvent, which is selected from one or more of water and ethanol.

5. a highly sensitive nitrite detection test paper according to claim 1, is characterized in that, The slurry further contains a reaction color developer, which is one or more substances containing phenolic hydroxyl groups selected from β-naphthol and N,N-dimethyl-m-hydroxyaniline. The mass concentration of the reaction color developer is 0-0.5 g / L.

6. A highly sensitive nitrite detection test paper according to claim 1, characterized in that, The test paper further comprises a substrate (2), one end of the substrate (2) being configured as a hand-held area (3), and the other end being configured as a detection area (1), wherein a detection base layer is adhered to the detection area (1).

7. A highly sensitive nitrite detection test paper according to claim 1, characterized in that, The method for using the test paper comprises the following steps: Immerse the test paper in the test liquid, shake off the excess liquid on the test paper, place the test paper horizontally facing upwards, and compare the reading with the colorimetric card to detect the nitrite ion concentration; The preparation method of the colorimetric card comprises the following steps: Immerse the test paper in nitrite solutions with different nitrite ion concentrations, shake off the excess liquid on the test paper, place the test paper horizontally with the face upwards, and make a standard colorimetric card with the same color tone according to the color of the test paper; The immersion temperature is 10-40°C and the time is 1-20 seconds. The placing temperature is 10-40° C. and the time is 10-45 seconds.

8. A method for preparing a highly sensitive nitrite detection test paper as claimed in any one of claims 1 to 7, characterized in that: The method comprises the following steps: The raw materials are mixed to form a liquid, the detection substrate is immersed in the liquid, and the liquid is dried at low temperature and reduced pressure to obtain a high-sensitivity nitrite detection test paper.

9. a preparation method of a highly sensitive nitrite detection test paper according to claim 8, is characterized in that, The immersion temperature is 10-40° C., and the immersion time is 5-30 seconds.

10. The method for preparing a highly sensitive nitrite detection test paper according to claim 8, wherein The temperature of the low-temperature reduced-pressure drying is 25 to 50° C., the vacuum degree is 0.1 to 20 Pa, and the time is 40 to 120 minutes.

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