High-sensitivity copper ion detection test paper and preparation method thereof

Abstract

The invention relates to high-sensitivity copper ion detection test paper and a preparation method thereof.The test paper comprises a detection base layer, the detection base layer contains a copper ion reaction substrate, the copper ion reaction substrate shows purple after making contact with copper ions, and different copper ion concentrations are distinguished through different color gradations of the color; the detection base layer is soaked in a feed liquid and then dried to obtain the high-sensitivity copper ion detection test paper, the feed liquid contains a copper ion reaction substrate and a reaction accelerator, the copper ion reaction substrate adopts 2, 2 '-biquinoline-4, 4'-dicarboxylic acid disodium salt, and the reaction accelerator adopts a bivalent copper ion reducing agent. 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 copper ion 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 copper ion detection test paper and a preparation method thereof. Background Art

[0002] Copper is a heavy metal. Industrial wastewater from industries like electroplating, metallurgy, and the chemical industry, which uses copper salts and compounds as catalysts, containing copper ions, can have a significant impact on the environment. Therefore, industrial wastewater from these copper-using factories and enterprises often requires testing for dissolved copper ions.

[0003] Disinfection methods such as electrolyzing sodium chloride solution to generate hypochlorous acid, which is then passed through a pool, are becoming increasingly popular. Electrolysis equipment often uses a copper rod as the positive electrode. As the electrolysis proceeds, the positive copper rod gradually releases copper ions, causing the copper ion concentration in the pool water to gradually increase. Excessive copper ion concentrations can irritate human skin. Therefore, if electrolytic disinfection equipment is used in swimming pools or spas, the copper ion concentration in the water must be monitored to prevent excessive concentrations.

[0004] Copper sulfate solution is a very common disinfectant used on leafy green vegetables. However, copper sulfate residues are harmful to human health. Therefore, regulations require that copper sulfate residues be removed from the surface of leafy green vegetables sold commercially. Currently, many vegetable wholesalers and retailers still use copper sulfate solution to preserve leafy greens. Therefore, testing vegetable samples for copper ion content is of practical significance.

[0005] Some copper ion detection test strips on the market currently have low sensitivity, with unclear color gradation at copper ion concentrations below 10ppm. This is primarily due to the fact that traditional copper ion detection test strips use sodium diethyldithiocarbamate as the reaction substrate, which forms a lighter complex product with copper ions, resulting in lower sensitivity.

[0006] Patent CN112683831A discloses a method for ultraviolet-visible detection of copper ions based on sulfazo compounds and their application in test strips. 2-p-Toluenesulfonamido-azobenzene is synthesized from 2,2'-diaminoazobenzene and p-toluenesulfonyl chloride. This compound coordinates with copper(II) ions, causing the test strip to change color from yellow to purple. This allows for highly selective and sensitive detection of copper ions based on color and UV spectrum changes. However, the test strips in this patent have similar colors at different concentration levels, making it difficult to distinguish between readings.

[0007] Patent CN111830021A discloses a highly selective test paper for detecting copper (II) ions and its preparation method. The test paper contains a reagent that changes color when exposed to copper (II) ions; the main component of the reagent is a hydrazone compound obtained by the reaction of 8-aminoquinoline and glutaraldehyde. The darker the color of the area on the test paper containing the test solution, the higher the copper (II) ion concentration in the test solution. A catalyst, hydrogen peroxide, is added dropwise to the area on the test paper containing the test solution. However, the test paper in this patent requires additional addition of the catalyst during use, and the amount and method of addition significantly affect the color of the test paper, making its use relatively cumbersome.

[0008] Patent CN111253388A discloses a method for preparing fluorescent probe test paper for detecting copper content in wastewater. The method involves reacting 4-chloro-8-hydroxy-2-methylquinoline with a series of raw materials, such as iodomethane or dimethyl sulfate, to produce an organic small molecule fluorescent material. However, the test paper in this patent requires supporting equipment, which is not conducive to rapid and simple detection.

[0009] Patent CN102472745A discloses a quantitative and self-calibrated chemical assay using a paper-based microfluidic system. In this assay, copper (II) ions in an indicator solution are reduced to copper (I) ions by uric acid preloaded on a test zone. The copper (I) ions then react with sodium biquinolinol dicarboxylate to form a purple chelate. However, the copper ion reducing agent in this patent takes a long time to react with copper ions, hindering rapid display of results. Summary of the Invention

[0010] The purpose of the present invention is to provide a highly sensitive copper ion detection test paper and a preparation method thereof in order to overcome at least one defect of the above-mentioned prior art. The present invention has the characteristics of accurate concentration indication and high sensitivity. Especially when the copper ion concentration is low, the color levels of different concentrations are clear.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] One of the technical solutions of the present invention is to provide a highly sensitive copper ion detection test paper, which includes a detection base layer containing a copper ion reaction substrate. The copper ion reaction substrate turns purple after contact with copper ions, and different color levels can clearly distinguish different copper ion concentrations.

[0013] The detection base layer is immersed in a slurry and then dried to obtain a high-sensitivity copper ion detection test paper. The copper ion reaction substrate is attached to the surface of the detection base layer. The slurry contains a copper ion reaction substrate and a reaction accelerator. The copper ion reaction substrate is 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt, and the reaction accelerator is a divalent copper ion reducing agent.

[0014] As a preferred technical solution, the detection base layer is made of filter paper.

[0015] Furthermore, the reaction accelerator is selected from one or more divalent copper ion reducing agents selected from cysteine, serine, arginine, sodium thiosulfate, sodium sulfite, sodium metabisulfite, and sodium ascorbate.

[0016] Furthermore, the mass ratio of the copper ion reaction substrate to the reaction accelerator is 1:(2-8), the mass concentration of the copper ion reaction substrate in the feed solution is 0.2-2 g / L, and the mass concentration of the reaction accelerator is 0.1-10 g / L.

[0017] As a preferred technical solution, the mass ratio of the copper ion reaction substrate to the reaction accelerator is 1:(4-6), the mass concentration of the copper ion reaction substrate in the feed solution is 0.7-1.5 g / L, and the mass concentration of the reaction accelerator is 2.5-7.5 g / L.

[0018] Furthermore, the feed liquid also contains a solvent, and the solvent is selected from one or more of water and ethanol.

[0019] Furthermore, the feed solution further contains a surfactant, which is selected from one or more of polyethylene glycol, polyoxyethylene sorbitan fatty acid ester, and sodium lauryl sulfate solution, and the volume fraction of the surfactant is 0-2%.

[0020] As a preferred technical solution, the molecular weight of the polyethylene glycol is 400-1000, the polyoxyethylene sorbitan fatty acid ester is Tween-20, and the solvent of the sodium lauryl sulfate solution is water with a concentration of 1-10%.

[0021] As a preferred technical solution, the surfactant is selected from one or more of polyethylene glycol and polyoxyethylene sorbitan fatty acid ester, and the volume fraction of the surfactant is 0.5-1.5%.

[0022] 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.

[0023] As a preferred technical solution, the material of the substrate is selected from polyethylene terephthalate (PET) or polyvinyl chloride (PVC) plastic.

[0024] Furthermore, the method for using the test paper (highly sensitive copper ion detection method) comprises the following steps:

[0025] Immerse the test paper in the test liquid, shake off the excess liquid on the test paper, place the test paper horizontally with the top facing up, and compare the reading with the colorimetric card to detect the copper ion concentration;

[0026] The preparation method of the colorimetric card comprises the following steps:

[0027] Immerse the test paper in divalent copper salt solutions with different copper 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;

[0028] The immersion temperature is 10-40°C and the time is 1-20 seconds.

[0029] The placing temperature is 10-40° C. and the time is 10-45 seconds.

[0030] As a preferred technical solution, the divalent copper salt is selected from one or more of copper sulfate, copper nitrate, and copper chloride, and the solvent of the divalent copper salt solution is water.

[0031] The copper ion concentration detected by the test paper is 0.8 to 20 mg / L (ppm).

[0032] One of the technical solutions of the present invention is to provide a method for preparing the highly sensitive copper ion detection test paper, the method comprising the following steps:

[0033] 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 highly sensitive copper ion detection test paper.

[0034] Furthermore, the immersion temperature is 10-40° C., and the immersion time is 5-30 seconds.

[0035] 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.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (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 quickly detect the copper ion content, and is easy to use; the test reagent usage is less than that of the laboratory method, 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;

[0038] (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;

[0039] (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, high safety, etc., especially when the copper ion concentration is low, the color levels of different concentrations are clear;

[0040] (4) The reaction substrate of the present invention can react with the copper ions reduced to divalent by the reaction accelerator to form a complex with a color different from the original color of the reaction substrate, thereby achieving the function of indicating the concentration of copper ions. The color difference varies greatly with the concentration, which is convenient for reading. The surfactant assists the reaction substrate and the reaction accelerator to quickly penetrate and evenly distribute on the detection base layer, avoiding uneven color development caused by local concentration differences. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the structure of a high-sensitivity copper ion detection test paper in an embodiment of the present invention;

[0042] Figure 2 Graph showing the relationship between the color of the standard colorimetric card and the copper ion concentration in an embodiment of the present invention.

[0043] Description of the marks in the figure:

[0044] 1—Detection area, 2—Substrate, 3—Handheld area. DETAILED DESCRIPTION

[0045] 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.

[0046] 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.

[0047] Example 1:

[0048] A highly sensitive copper ion 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 copper ion reaction substrate. The copper ion reaction substrate turns purple after contacting copper ions, and different color levels can clearly distinguish different copper ion concentrations.

[0049] The preparation method of the above-mentioned highly sensitive copper ion detection test paper comprises the following specific steps:

[0050] S1.1. Weigh 0.1 g of 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt and 0.5 g of cysteine, add 100 mL of pure water, and stir at 25°C until the solids are completely dissolved to obtain a slurry. Completely immerse chromatography-grade filter paper in the slurry at 25°C. After 10 seconds, remove the filter paper and place it in an oven at 40°C and a vacuum of 10 Pa for 80 minutes. The copper ion reaction substrate adheres to the surface of the detection substrate, obtaining a detection substrate that meets the requirements.

[0051] 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 copper ion detection test paper is obtained.

[0052] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity copper ion detection test paper comprises the following specific steps:

[0053] S2.1. Prepare copper ion standard solutions of different concentrations using copper sulfate and pure water at 25°C.

[0054] Weigh 0.39 g of copper sulfate pentahydrate (or 0.25 g of anhydrous copper sulfate) into a 1000 mL volumetric flask. Dissolve the solution in 200 mL of pure water. Dilute to the mark with pure water and mix thoroughly to obtain a 100 mg / L (ppm) copper ion standard stock solution.

[0055] Pipette 10.0 mL of 100 mg / L copper ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 10 mg / L (ppm) copper ion standard solution.

[0056] Pipette 5.0 mL of 100 mg / L copper ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 5 mg / L (ppm) copper ion standard solution.

[0057] Pipette 2.0 mL of 100 mg / L copper ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 2 mg / L (ppm) copper ion standard solution.

[0058] Pipette 1.0 mL of 100 mg / L copper ion standard stock solution into a 100 mL volumetric flask, dilute to the mark with pure water, and mix well to obtain a 1 mg / L (ppm) copper ion standard solution.

[0059] S2.2. Immerse the test paper in copper ion standard solutions with different copper 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.

[0060] When the copper ion concentration is 1-10 mg / L, the color levels of different concentrations are clear.

[0061] The highly sensitive copper ion detection test paper is tested or tested as follows, and then the test or test results are analyzed.

[0062] Test Example 1:

[0063] The anti-interference test of the above-mentioned high-sensitivity copper ion detection test paper is carried out. The specific steps are as follows:

[0064] Prepare 100 mg / L (ppm) sodium chloride solution, calcium chloride solution, magnesium sulfate solution and 20 mg / L (ppm) zinc chloride solution respectively, and mix the prepared solutions with 10 mg / L copper ion standard solution at a volume ratio of 1:1 to obtain interference group solutions;

[0065] 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 copper ion concentration.

[0066] The test paper in this embodiment was used for anti-interference testing of interference group solutions of sodium ions, calcium ions, magnesium ions and zinc 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 sodium ions, calcium ions, magnesium ions and zinc ions.

[0067] Test Example 2:

[0068] The detection upper limit test of the above-mentioned high-sensitivity copper ion detection test paper is carried out as follows:

[0069] Referring to the preparation of copper ion standard solution, 100 mg / L copper ion standard stock solution was used to prepare 20 mg / L (ppm), 30 mg / L (ppm), 40 mg / L (ppm) and 50 mg / L (ppm) copper ion solutions respectively;

[0070] Immerse the test paper in copper 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 copper ion concentration.

[0071] The test paper in this embodiment was used to test the upper limit of detection of copper ion solutions of different concentrations. It was found that for copper ion solutions above 30 mg / L, the test paper color was dark purple and could not be distinguished; for 20 mg / L copper ion solution, the test paper color was dark purple, which was slightly different from the color of 10 mg / L copper ion solution but not obvious; that is, the upper limit of detection of the test paper was 20 mg / L.

[0072] Test Example 3:

[0073] The detection limit test of the above-mentioned high-sensitivity copper ion detection test paper is carried out, and the specific steps are as follows:

[0074] Referring to the preparation of copper ion standard solution, 10 mg / L copper ion standard solution was used to prepare 0.1 mg / L (ppm), 0.2 mg / L (ppm), 0.4 mg / L (ppm) and 0.8 mg / L (ppm) copper ion solutions respectively;

[0075] Immerse the test paper in copper 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 copper ion concentration.

[0076] The test paper in this embodiment was used to test the detection limit of copper ion solutions of different concentrations. It was found that for copper ion solutions below 0.4 mg / L, the test paper showed white color without color; for 0.8 mg / L copper ion solution, the test paper showed light purple, which was slightly different from the color of 1 mg / L copper ion solution but not obvious; that is, the detection limit of the test paper was 0.8 mg / L.

[0077] Example 2:

[0078] A highly sensitive copper ion detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.05 g of 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt and 0.1 g of sodium sulfite are weighed.

[0079] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity copper ion detection test paper is the same as that in Example 1.

[0080] 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 2 mg / L, the upper limit remained 20 mg / L, the detection limit range was narrowed, and the sensitivity decreased, reflecting that the reduction in the concentration of the copper ion reaction substrate would affect the detection limit range and sensitivity. The anti-interference ability was basically the same as that in Example 1.

[0081] Example 3:

[0082] A highly sensitive copper ion detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.1 g of 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt and 0.5 g of sodium ascorbate are weighed, 50 mL of pure water are first added, and the mixture is stirred at 25°C until the solid is completely dissolved, and then 50 mL of ethanol is added and stirred at 25°C until the mixture is clarified to obtain a feed solution.

[0083] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity copper ion detection test paper is the same as that in Example 1.

[0084] The test paper in Example 3 was used for testing. Compared with Example 1, the difference in color development of the test paper was still obvious, and the detection limit range, sensitivity and anti-interference ability were basically the same as those in Example 1.

[0085] Example 4:

[0086] A highly sensitive copper ion detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.1 g of 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt and 0.5 g of sodium ascorbate are weighed, 50 mL of pure water are first added, and the mixture is stirred at 25° C. until all the solids are dissolved. 49 mL of ethanol and 1 mL of polyethylene glycol-800 are then added, and the mixture is stirred at 25° C. until the mixture is clear to obtain a feed solution.

[0087] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity copper ion detection test paper is the same as that in Example 1.

[0088] The test paper in Example 4 was used for testing. Compared with Example 3, the difference in color development of the test paper was still obvious, and the detection limit range, sensitivity and anti-interference ability were basically the same as those in Example 3.

[0089] Example 5:

[0090] A highly sensitive copper ion detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.1 g of 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt and 0.5 g of sodium ascorbate are weighed, 50 mL of pure water are first added, and the mixture is stirred at 25° C. until all the solids are dissolved. 49 mL of ethanol and 1 mL of Tween-20 are then added, and the mixture is stirred at 25° C. until the mixture is clear to obtain a feed solution.

[0091] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity copper ion detection test paper is the same as that in Example 1.

[0092] The test paper in Example 5 was used for testing. Compared with Example 3, the difference in color development of the test paper was still obvious, and the detection limit range, sensitivity and anti-interference ability were basically the same as those in Example 3.

[0093] Example 6:

[0094] A highly sensitive copper ion detection test paper and a preparation method thereof are substantially the same as those in Example 1, except that, in step S1.1, 0.1 g of 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt and 0.5 g of sodium ascorbate are weighed, 50 mL of pure water are first added, and the mixture is stirred at 25° C. until all the solids are dissolved. 48 mL of ethanol and 2 mL of a 5% aqueous solution of sodium dodecylsulfonate are then added, and the mixture is stirred at 25° C. until the mixture becomes clear to obtain a feed solution.

[0095] The preparation method of the colorimetric card required for the above-mentioned high-sensitivity copper ion detection test paper is the same as that in Example 1.

[0096] The test paper in Example 6 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 2 mg / L, while the upper limit remained at 20 mg / L. The detection limit range was narrowed and the sensitivity decreased, indicating that the addition of some surfactants would affect the detection limit range and sensitivity. The anti-interference ability was basically the same as that in Example 1.

[0097] 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 copper ion detection test paper, characterized in that, The test paper includes a detection base layer, which contains a copper ion reaction substrate. The copper ion reaction substrate turns purple after contacting copper ions, and different color levels distinguish different copper ion concentrations. The detection substrate is immersed in a liquid and then dried to obtain a high-sensitivity copper ion detection test paper. The liquid contains a copper ion reaction substrate and a reaction accelerator. The copper ion reaction substrate is 2,2'-biquinoline-4,4'-dicarboxylic acid disodium salt, and the reaction accelerator is a divalent copper ion reducing agent.

2. A highly sensitive copper ion detection test paper according to claim 1, characterized in that, The reaction accelerator is selected from one or more divalent copper ion reducing agents selected from cysteine, serine, arginine, sodium thiosulfate, sodium sulfite, sodium metabisulfite, and sodium ascorbate.

3. A highly sensitive copper ion detection test paper according to claim 1, characterized in that, The mass ratio of the copper ion reaction substrate to the reaction accelerator is 1:(2-5), the mass concentration of the copper ion reaction substrate in the feed solution is 0.5-1 g / L, and the mass concentration of the reaction accelerator is 0.1-10 g / L.

4. A highly sensitive copper ion detection test paper according to claim 1, 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 copper ion detection test paper according to claim 4, characterized in that, The feed liquid further contains a surfactant, which is selected from one or more of polyethylene glycol, polyoxyethylene sorbitan fatty acid ester, and sodium lauryl sulfonate solution. The volume fraction of the surfactant is 0-2%.

6. A highly sensitive copper ion 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 copper ion 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 copper ion concentration; The preparation method of the colorimetric card comprises the following steps: Immerse the test paper in divalent copper salt solutions with different copper 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 immersion 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 copper ion detection test paper according to 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 highly sensitive copper ion detection test paper.

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

Images