Ph test strip, and preparation method therefor and use thereof

Abstract

The present application provides a pH test strip, and a preparation method therefor and a use thereof. The pH test strip comprises a substrate and a reagent-loaded layer, wherein the reagent-loaded layer is arranged on the substrate. The reagent-loaded layer contains a pH developer and a cationic organic salt. The preparation method for the pH test strip of the present application comprises: mixing the substrate and a pH developer-containing solution, and carrying out first drying to obtain a first material; and then mixing the first material and a cationic organic salt-containing solution, and carrying out second drying to obtain the pH test strip. The present application can avoid fall-off of a pH developer during testing, and achieve uniform color development during testing and high test accuracy.

Description

A pH test strip, its preparation method and application Technical Field

[0001] This application relates to the field of pH test strips, and more particularly to a pH test strip, its preparation method, and its application. Background Technology

[0002] pH is one of the important parameters for evaluating water quality, and there are various mature testing technologies for it. Among them, the solid-state testing method—pH test strips—has advantages such as low cost, no maintenance, long shelf life, easy recycling, and adjustable size according to testing needs. It works by fixing various pH indicators on the test strip, dropping the solution to be tested onto the test strip or directly contacting the test strip with the solution, and then comparing the color change of the test strip with a standard colorimetric card to obtain the pH value of the solution.

[0003] The colorimetric principle of pH test strips is based on the color-changing property of acid-base indicators. An acid-base indicator is a compound that changes color with the pH of a solution. Its molecules contain functional groups that can accept or release protons. When the solution is acidic, the proton concentration is high, and the indicator molecules accept protons, causing a change in molecular structure and thus changing color. Conversely, when the solution is alkaline, the proton concentration is low, and the indicator molecules release protons, causing a change in molecular structure and also changing color.

[0004] The general method for making pH test strips is to immerse the test strip base paper directly in pH indicator solutions of different proportions for a period of time, and then produce pH test strips of different specifications through processes such as rolling and drying.

[0005] However, during testing, as the liquid spreads on the test strip, the indicator on the test strip dissolves and moves with the liquid, resulting in inconsistent color changes in the color development area on the test strip. Furthermore, the dissolved indicator can fall into the test liquid, causing contamination and leading to reading errors. Consequently, the test strip test has poor repeatability.

[0006] Therefore, it is necessary to develop new types of pH test strips to solve the problems of indicator leakage and uneven color development. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a pH test strip, its preparation method, and its application. By adding a cationic organic salt, the leakage of the pH colorimetric reagent into the liquid phase can be prevented or limited, and the pH colorimetric reagent can be avoided from contaminating the test liquid phase. Furthermore, the accuracy of the pH test strip can be further improved.

[0008] To achieve this objective, the following technical solution is adopted in this application:

[0009] In a first aspect, this application provides a pH test strip, the pH test strip comprising a substrate and a reagent loading layer, the reagent loading layer being disposed on the substrate; the reagent loading layer comprising a pH colorimetric agent and a cationic organic salt.

[0010] This application utilizes cationic organic salts to immobilize the pH colorimetric reagent on the substrate, thereby preventing leakage or transfer of the pH colorimetric reagent during the detection process. Compared to existing pH test strips, this application has the following characteristics:

[0011] A. Since the pH colorimetric reagent may transfer or leak during the pH test strip detection process, such transfer or leakage can easily lead to uneven pH colorimetric reagent content on the test strip, resulting in low accuracy of subsequent colorimetric detection. This application uses cationic organic salt to fix the pH colorimetric reagent, which can ensure the uniformity of pH colorimetric reagent distribution on the test strip during the detection process and improve the accuracy of detection.

[0012] B. This application uses cationic organic salts for fixation, which can avoid the problem of pH colorimetric reagent leaking into the test solution and causing contamination of the test solution;

[0013] C. This application can avoid the problem that leakage of pH colorimetric reagent leads to a decrease in the concentration of pH colorimetric reagent on the original test strip compared to the theoretical value, resulting in a lower colorimetric concentration than the actual data, thereby further improving the accuracy of detection.

[0014] Preferably, the pH colorimetric agent has anionic groups, and the cationic organic salt has ionic bonds connecting the anionic groups to each other.

[0015] In this application, the pH colorimetric reagent has anionic groups that can be linked to cationic organic salts through ionic bonds. The cationic organic salts can form a mesh protective film on the surface of the reagent-supported layer. That is, ionic bonds are formed between the mesh protective film and the pH colorimetric reagent, which firmly confines the pH colorimetric reagent between the substrate and the mesh protective film, thus preventing leakage of the pH colorimetric reagent.

[0016] Preferably, the surface of the reagent-supported layer has a mesh-like protective film formed by cationic organic salts, and the mesh-like protective film is connected to the pH colorimetric agent through ionic bonds and / or electrostatic adsorption.

[0017] In this application, the protective film has a micro-network structure with multiple connection points for the pH colorimetric reagent, which greatly improves the fixation effect of the pH colorimetric reagent.

[0018] Preferably, the pH colorimetric agent penetrates into the substrate and adheres to the substrate surface.

[0019] Preferably, the substrate has cationic groups, and the pH colorimetric agent forms a crosslinking system with the cationic groups on the substrate.

[0020] It is worth noting that there are two main points to achieve the fixation of pH colorimetric reagent in this application. One is that the pH colorimetric reagent is interconnected with the network protective film formed by the cationic organic salt through ionic bonds, so that it does not move during the detection process. The other is that the pH colorimetric reagent is fixed to the substrate by ionic bonds, thereby encapsulating and fixing the pH colorimetric reagent on the substrate, thus achieving the fixation of the pH colorimetric reagent.

[0021] Preferably, the thickness of the mesh protective film is 0.2–2 μm, for example, it can be 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.8 μm, 1.9 μm or 2.0 μm.

[0022] Preferably, the cationic organic salt is a cationic high molecular weight organic salt.

[0023] Preferably, the cationic organic salt includes any one or a combination of at least two of polyquaternary ammonium salt, cationic polyacrylamide, chitosan, or polydiallyl ammonium chloride, wherein typical but non-limiting combinations are a combination of polyquaternary ammonium salt and cationic polyacrylamide, a combination of chitosan and cationic polyacrylamide, a combination of polyquaternary ammonium salt and chitosan, or a combination of polydiallyl ammonium chloride and chitosan.

[0024] When selecting cationic organic salts, the following factors need to be considered: The substrate of the test strip is generally made of cotton fiber, the main component of which is cellulose. Cellulose molecules contain a large number of -OH groups, thus exhibiting excellent water absorption. The pH colorimetric reagent molecules adhere to the surface of the cellulose molecules. If an additional thin polymer mesh protective film is attached to the cellulose surface, it needs to be able to reduce the amount of indicator dissolved while maintaining the wetting speed of the test strip.

[0025] In addition, since pH color reagents are usually in the form of anionic salts and carry anionic groups, while the polymer mesh protective film has cationic groups, the two can form ionic bonds, binding the pH color reagent to the polymer mesh protective film. This effectively restricts the movement of the pH color reagent with the liquid phase, achieving a uniform color development effect.

[0026] To achieve the above effects, the basic requirements for cationic organic salts are:

[0027] (1) It has a large number of cationic groups: The polymer structure of cationic organic salts contains a large number of groups such as ammonium groups. These groups can provide cations to bind to pH color reagents with anions, and can also increase the hydrophilicity of the polymer and improve or maintain the water absorption performance of the test paper itself.

[0028] (2) It has film-forming stability: It can form a thin film (protective layer) on the surface of cellulose, and this film (protective layer) can remain stable in water for a short time (at least within 10 to 40 seconds when the test paper is used) without dissolving.

[0029] Based on the above-mentioned properties, this application preferably uses an ammonium-containing organic salt, such as any one or a combination of at least two of polyquaternary ammonium salts, cationic polyacrylamide, chitosan, or polydimethyldiallylammonium chloride, as a cationic organic salt, which can better achieve the following key points: 1. It can be fixed with the substrate through hydrogen bonds; 2. It can form ionic bonds and / or electrostatic adsorption with the pH colorimetric reagent; 3. It has excellent hydrophilic properties, which can improve or maintain water wettability; 4. After film formation, it can remain stable and insoluble in water within the detection time.

[0030] Specifically, quaternary ammonium salt groups can bind with anionic groups in the pH colorimetric reagent through ionic bonds; a large number of amide groups in polyacrylamide can form hydrogen bonds with hydroxyl groups in the substrate, forming a stable and uniform film on the test paper surface; the molecular structure of polydimethyldiallylammonium chloride is a cationic network structure, which can form hydrogen bonds with fibers to form a stable film on its surface, and there is electrostatic adsorption between the cations and the anions of the dye, thereby preventing the pH colorimetric reagent from detaching from the substrate surface.

[0031] Preferably, the polyquaternium salt comprises polyquaternium salt-10.

[0032] This application preferably uses polyquaternium-10, in which the quaternary ammonium salt groups in the molecule can be bonded to the anionic groups in the pH colorimetric agent through ionic bonds, thereby fixing it on the substrate and forming a thin film on the substrate surface to prevent the pH colorimetric agent from falling off.

[0033] Preferably, the cationic polyacrylamide has a weight-average molecular weight of 60,000 to 1,200,000, for example, 60,000, 100,000, 120,000, 150,000, 200,000, 500,000, 1,000,000 or 1,200,000, etc., and is preferably 100,000 to 600,000.

[0034] The preferred cationic polyacrylamide used in this application has a weight-average molecular weight of 60,000 to 1,200,000, which can better ensure the hydrophilicity of the mesh protective film and the fixation effect on the pH colorimetric agent.

[0035] Preferably, the weight-average molecular weight of the chitosan is 50,000 to 500,000, for example, it can be 50,000, 55,000, 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000 or 500,000, and more preferably 100,000 to 200,000.

[0036] This application preferably controls the weight-average molecular weight of chitosan within the above-mentioned range, which can ensure that the thickness of the mesh protective film is within a reasonable range, thereby better ensuring the reaction sensitivity of the test strip, while also taking into account the adhesion to the substrate, ensuring the fixation effect on the pH colorimetric reagent, and avoiding its own detachment in water or leakage of the pH colorimetric reagent.

[0037] Preferably, the weight-average molecular weight of the polydimethyldiallylammonium chloride is 100,000 to 500,000, for example, it can be 100,000, 120,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000 or 500,000, and more preferably 200,000 to 350,000.

[0038] The preferred polydimethyldiallyl ammonium chloride in this application has a weight-average molecular weight of 100,000 to 500,000. Due to its strong cationicity, it has a strong binding force with the fiber surface and the indicator, and has the advantage of stabilizing and fixing dye molecules.

[0039] Preferably, the pH colorimetric agent includes an anionic indicator.

[0040] Preferably, the anionic indicator is an anionic dye molecule.

[0041] Preferably, the anionic dye molecule comprises any one or a combination of at least two of the following: cresol red, soap yellow, bromochlorophenol blue, chlorophenol red, bromocresol violet, bromothymol blue, phenol red, m-cresol violet, phenolphthalein, alizarin yellow, or indigo carmine. Typical but non-limiting combinations include: cresol red and soap yellow; bromochlorophenol blue and soap yellow; cresol red and bromochlorophenol blue; chlorophenol red and soap yellow; cresol red and bromothymol blue; bromothymol blue and indigo carmine; phenol red and m-cresol violet; alizarin yellow and soap yellow; and indigo carmine and alizarin yellow. One indicator can be selected as the indicator for the narrow-range, high-precision test paper, or two or more of these indicators can be selected as the indicators for the wide-range test paper.

[0042] Preferably, the reagent loading density on the pH test strip is 1.5–10 mg / cm³. 3 For example, it could be 1.5 mg / cm³ 3 2mg / cm 3 2.5 mg / cm 3 3mg / cm 3 4mg / cm 3 4.5 mg / cm 35mg / cm 3 6mg / cm 3 6.5 mg / cm 3 7mg / cm 3 8mg / cm 3 9mg / cm 3 Or 10mg / cm 3 wait.

[0043] Secondly, this application provides a method for preparing the pH test strip described in the first aspect, the method comprising:

[0044] A first material is obtained by mixing a substrate and a solution containing a pH colorimetric agent and then performing a first drying process. The first material is then mixed with a solution containing a cationic organic salt and subjected to a second drying process to obtain the pH test paper.

[0045] The preparation method provided in the second aspect of this application can produce the pH test paper described in the first aspect, which has excellent performance, a simple preparation process, and broad application prospects. This application requires first impregnating the paper with a pH colorimetric reagent and then with a solution containing a cationic organic salt, using a mesh protective film to fix the pH colorimetric reagent inside.

[0046] This application does not impose any special restrictions on the solid-liquid ratio of the substrate and solution in the above process. Any solid-liquid ratio form known to those skilled in the art can be used as long as the substrate is sufficiently wetted.

[0047] Preferably, the first drying and the second drying are each independently vacuum drying.

[0048] Preferably, the mixed substrate and the solution containing the pH colorimetric agent are immersed for 8 to 15 seconds, for example, 8 seconds, 9 seconds, 10 seconds, 11 seconds, 12 seconds, 13 seconds, 14 seconds or 15 seconds, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the first material and the solution containing the cationic organic salt are mixed and immersed for 25 to 35 seconds, for example, 25 seconds, 27 seconds, 28 seconds, 29 seconds, 30 seconds, 31 seconds, 32 seconds, 33 seconds, 34 seconds or 35 seconds, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the concentration of the pH colorimetric reagent in the solution containing the pH colorimetric reagent is 0.25 to 1.5 mM, for example, it can be 0.25 mM, 0.39 mM, 0.53 mM, 0.67 mM, 0.81 mM, 0.95 mM, 1.09 mM, 1.23 mM, 1.37 mM or 1.5 mM, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 0.75 to 1.25 mM.

[0051] Preferably, the solvent in the solution containing the pH colorimetric agent includes ethanol and water, wherein the volume ratio of ethanol to water is 0.25:1 to 9:1, for example, it can be 0.25:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, 0.85:1 or 0.9:1, etc., and preferably 1.25:1 to 9:1.

[0052] Preferably, the solution containing the pH colorimetric agent also contains a pH adjuster.

[0053] This application does not have special requirements for pH adjusters. Depending on the different pH-containing colorimetric agents, different pH values ​​need to be controlled. For example, pH adjusters can be dilute hydrochloric acid and NaOH solution.

[0054] Preferably, the concentration of the cationic organic salt in the solution containing the cationic organic salt is 0.1 wt% to 3.0 wt%, for example, it can be 0.1 wt%, 0.5 wt%, 0.8 wt%, 1.1 wt%, 1.4 wt%, 1.8 wt%, 2.1 wt%, 2.4 wt%, 2.7 wt%, or 3.0 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 0.3 wt% to 1.0 wt%.

[0055] This application preferably controls the concentration of cationic organic salt within the above-mentioned range, which can better control the viscosity of the solution containing cationic organic salt within the range of 80 to 600 mPa·s, thereby ensuring the adhesion of the mesh protective film to the substrate and the reaction sensitivity of the test paper, while improving the detection accuracy and avoiding the transfer and leakage of pH colorimetric reagent.

[0056] Preferably, the solvent of the solution containing the cationic organic salt includes water.

[0057] Preferably, the solution containing the cationic organic salt also contains a pH adjuster, which can be selected as dilute hydrochloric acid and NaOH solution, depending on the required pH adjustment.

[0058] As a preferred technical solution of this application, the preparation method includes the following steps:

[0059] The substrate is first immersed in ethanol and / or aqueous solution with a pH colorimetric reagent concentration of 0.25-1.5mM, excess water is squeezed out and dried to obtain the first material.

[0060] The first material is then immersed in an aqueous solution containing 0.1 wt% to 3.0 wt% cationic organic salt, excess water is squeezed out and the material is dried to obtain the pH test paper.

[0061] This application does not impose any special restrictions on the substrate material. Any substrate material for test strips that is well known to those skilled in the art can be used. Adjustments can also be made according to the actual situation, such as using cellulose paper, filter paper, or absorbent cotton paper.

[0062] Thirdly, this application provides an application of the pH test strip described in the first aspect in pH detection, preferably in liquid phase pH detection.

[0063] The pH test strip provided in the third aspect of this application can be well applied in pH detection.

[0064] Compared with the prior art, this application has at least the following beneficial effects:

[0065] (1) The pH test strip provided in this application forms a mesh protective film by adding cationic organic salts. The cationic organic salts "bridge" between the pH colorimetric agent and the paper cellulose, and simultaneously crosslink with the pH colorimetric agent molecules and cellulose to form a highly diversified crosslinked system. The pH colorimetric agent is fixed between the test strip fibers and the mesh protective film, making the pH colorimetric agent more firmly bonded to the paper and preventing the indicator molecules from falling off the fibers. At the same time, the cationic organic salts form a three-dimensional mesh film on the fiber surface, which can seal the indicator inside. During the test, water molecules are allowed to penetrate in to make the indicator colorimetric, but the indicator molecules are not allowed to detach from the fibers and fall into the water, so that the test strip colorimetric is uniform and does not contaminate the test solution.

[0066] (2) When the pH test strip provided in this application is used to test actual water samples, the color distribution on the surface of the test strip is uniform and the color changes more obviously with the index to be tested. This can significantly improve the resolution and recognition accuracy of the color card, and the test accuracy is above 90% and the resolution is within 0.4.

[0067] (3) When the pH test strip provided in this application detects pH, due to the presence of the mesh protective film, it can increase the contact time between the test strip and the test liquid. The test strip is preferably soaked in the aqueous phase for more than 1 minute without discoloration. This causes hydrogen ions or hydroxide ions in the water to accumulate on the test strip, thereby enhancing the color response of the test strip, making the color development effect stronger, and significantly improving the visual resolution and recognition accuracy of the color card. Detailed Implementation

[0068] To facilitate understanding of this application, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of this application.

[0069] Example 1

[0070] This embodiment provides a pH test strip, which includes a substrate and a reagent loading layer, wherein the reagent loading layer is disposed on the substrate;

[0071] The reagent-supported layer contains a pH colorimetric agent and a cationic organic salt; the pH colorimetric agent has anionic groups, and the cationic organic salt and the anionic groups are connected by ionic bonds. The surface of the reagent-supported layer has a mesh-like protective film formed by the cationic organic salt; the substrate has cationic groups, and the pH colorimetric agent and the cationic groups on the substrate form a cross-linked system.

[0072] The thickness of the mesh protective film is 0.8 μm. The cationic organic salt is polyquaternium-10. The pH colorimetric agent is phenol red.

[0073] The reagent loading density of the pH test strip is 6.6 mg / cm³. 3 .

[0074] The preparation method of the pH test strip includes the following steps:

[0075] Cellulose test paper was first immersed in an ethanol and aqueous solution of 1mM phenol red at pH 7.9 (volume ratio 7:3) for 10 seconds, then the excess water was squeezed out and dried to obtain the first material.

[0076] The first material is then immersed in an aqueous solution containing 0.5 wt% polyquaternium-10 (viscosity 200 mPa·s) for 30 s, excess water is squeezed out and dried to obtain the pH test paper.

[0077] Example 2

[0078] This embodiment provides a pH test strip, which includes a substrate and a reagent loading layer, wherein the reagent loading layer is disposed on the substrate;

[0079] The reagent-supported layer contains a pH colorimetric agent and a cationic organic salt; the pH colorimetric agent has anionic groups, and the cationic organic salt and the anionic groups are connected by ionic bonds. The surface of the reagent-supported layer has a mesh-like protective film formed by the cationic organic salt; the substrate has cationic groups, and the pH colorimetric agent and the cationic groups on the substrate form a cross-linked system.

[0080] The thickness of the mesh protective film is 1.0 μm. The cationic organic salt is cationic polyacrylamide with a molecular weight of 200,000. The pH colorimetric agent is cresol red.

[0081] The reagent loading density on the pH test strip is 6.2 mg / cm³. 3 .

[0082] The preparation method of the pH test strip includes the following steps:

[0083] Cellulose test paper was first immersed in an ethanol and aqueous solution of 1mM cresol red at pH 8.2 (volume ratio 7:3) for 10 seconds, then squeezed to remove excess water and dried to obtain the first material.

[0084] The first material is then immersed in an aqueous solution (viscosity 260 mPa·s) containing 0.8 wt% cationic polyacrylamide with a molecular weight of 200,000 for 30 seconds, excess water is squeezed out and the material is dried to obtain the pH test paper.

[0085] Example 3

[0086] This embodiment provides a pH test strip, which includes a substrate and a reagent loading layer, wherein the reagent loading layer is disposed on the substrate;

[0087] The reagent-supported layer contains a pH colorimetric agent and a cationic organic salt; the pH colorimetric agent has anionic groups, and the cationic organic salt and the anionic groups are connected by ionic bonds. The surface of the reagent-supported layer has a mesh-like protective film formed by the cationic organic salt; the substrate has cationic groups, and the pH colorimetric agent and the cationic groups on the substrate form a cross-linked system.

[0088] The thickness of the mesh protective film is 1.9 μm. The cationic organic salt is chitosan with a molecular weight of 100,000. The pH colorimetric agent is bromothymol blue.

[0089] The reagent loading density on the pH test strip is 8.5 mg / cm³. 3 .

[0090] The preparation method of the pH test strip includes the following steps:

[0091] Cellulose test paper was first immersed in an ethanol and aqueous solution of 1.25 mM bromothymol blue at pH 7.0 (volume ratio 2:8) for 15 seconds, then the excess water was squeezed out and dried to obtain the first material.

[0092] The first material is then immersed in an aqueous solution containing 3.0 wt% chitosan with a molecular weight of 100,000 (viscosity 600 mPa·s) for 25 s, excess water is squeezed out and dried to obtain the pH test paper.

[0093] Example 4

[0094] This embodiment provides a pH test strip, which includes a substrate and a reagent loading layer, wherein the reagent loading layer is disposed on the substrate;

[0095] The reagent-supported layer contains a pH colorimetric agent and a cationic organic salt; the pH colorimetric agent has anionic groups, and the cationic organic salt and the anionic groups are connected by ionic bonds. The surface of the reagent-supported layer has a mesh-like protective film formed by the cationic organic salt; the substrate has cationic groups, and the pH colorimetric agent and the cationic groups on the substrate form a cross-linked system.

[0096] The thickness of the mesh protective film is 1.8 μm. The cationic organic salt is polydimethyldiallyl ammonium chloride with a molecular weight of 300,000. The pH colorimetric agent is m-cresol purple.

[0097] The reagent loading density on the pH test strip is 5.3 mg / cm³. 3 .

[0098] The preparation method of the pH test strip includes the following steps:

[0099] Cellulose test paper was first immersed in an ethanol and aqueous solution (volume ratio 9:1) of 0.75mM m-cresol purple at pH 8.32 for 8 seconds, then squeezed out excess water and dried to obtain the first material.

[0100] The first material is then immersed in an aqueous solution containing 3.0 wt% polydimethyldiallyl ammonium chloride with a molecular weight of 300,000 (viscosity 560 mPa·s) for 35 seconds, excess water is squeezed out and dried to obtain the pH test paper.

[0101] Example 5

[0102] This embodiment provides a pH test strip. Except for the molecular weight of the cationic polyacrylamide being 80,000, the pH test strip is the same as that in Example 2, and will not be described again here.

[0103] Example 6

[0104] This embodiment provides a pH test strip. Except for the molecular weight of chitosan being 80,000, the pH test strip is the same as that in Example 3, and will not be described again here.

[0105] Example 7

[0106] This embodiment provides a pH test strip. Except for the molecular weight of polydimethyldiallylammonium chloride being 150,000, the pH test strip is the same as that in Example 4, and will not be described again here.

[0107] Example 8

[0108] This embodiment provides a pH test strip. Except for the molecular weight of the cationic polyacrylamide being 1.3 million, the pH test strip is the same as that in Example 2, and will not be described again here.

[0109] Example 9

[0110] This embodiment provides a pH test strip. Except for the molecular weight of chitosan being 600,000, the pH test strip is the same as that in Example 3, and will not be described again here.

[0111] Example 10

[0112] This embodiment provides a pH test strip. Except for the molecular weight of polydimethyldiallyl ammonium chloride being 600,000, the pH test strip is the same as that in Example 4, and will not be described again here.

[0113] Example 11

[0114] This embodiment provides a pH test strip. The pH test strip is the same as in Example 1 except that 0.5 wt% of polyquaternium-10 is replaced with 0.05 wt% of polyquaternium-10, and will not be described again here.

[0115] Example 12

[0116] This embodiment provides a pH test strip. Except for replacing 0.5 wt% polyquaternium-10 with 3.5 wt% polyquaternium-10, the pH test strip is the same as in Example 1, and will not be repeated here.

[0117] Example 13

[0118] This embodiment provides a pH test strip. Except that polyquaternium-10 is replaced with trimethylammonium bromide, the pH test strip is the same as in Example 1, and will not be described again here.

[0119] Comparative Example 1

[0120] This comparative example provides a pH test strip, which is the same as that in Example 1 except that polyquaternium-10 is replaced with sodium carboxymethyl cellulose, and will not be described again here.

[0121] Comparative Example 2

[0122] This comparative example provides a pH test strip, which is the same as that in Example 1 except that polyquaternium-10 is replaced with hydroxyethyl cellulose with a molecular weight of 20,000, and will not be described again here.

[0123] Comparative Example 3

[0124] This comparative example provides a pH test strip, which is the same as that in Example 1 except that polyquaternium-10 is replaced with sodium hyaluronate with a molecular weight of 80,000, and will not be described again here.

[0125] Test method: After preparation, the test strips are cut into 5mm × 5mm squares and attached to strips of PVC. pH standard solutions are prepared according to a gradient of 0.2 pH intervals, and their pH is measured using a pH meter.

[0126] The prepared test strips were used to test the pH standard solution. The test strip was immersed in the solution to be tested for 3 seconds and then removed. Excess water was shaken off and the color of the test strip was extracted within 30 seconds to draw a standard color card.

[0127] The pH standard solution was tested using prepared pH test strips. The tester did not know the specific pH value and instead compared the reading to a color chart. If the reading on the color chart matched the pH of the tested solution, the comparison was considered correct; otherwise, it was incorrect. Three parallel tests were conducted.

[0128] Immerse the test strip in the solution for 1 minute, then remove it and observe whether the color has come off.

[0129] The test results of the above embodiments and comparative examples are shown in Table 1.

[0130] Table 1

[0131] The following points can be observed from Table 1:

[0132] (1) As can be seen from the comprehensive examples 1 to 4, the pH test strip provided in this application can significantly prolong the contact time between the pH test strip and the test liquid by setting cationic organic salt on the reagent loading layer to form a mesh protective film. The test strip will not discolor for a long time of more than 1 minute when immersed in the aqueous phase; moreover, the resolution is within 0.4 and the test accuracy reaches more than 90%, with good detection effect.

[0133] (2) As can be seen from Examples 2-4 and Examples 5-10, this application controls the weight-average molecular weight of cationic organic salts within a reasonable range. On the one hand, it can avoid the decrease in detection resolution caused by excessive molecular weight; on the other hand, it can ensure the formation of a sufficient network protective film, thereby slowing down the dissolution rate of the pH colorimetric reagent, thereby extending the maximum soaking time and improving the detection effect.

[0134] (3) As can be seen from the combined examples 1 and 11-12, the concentration of polyquaternium-10 in the aqueous solution of polyquaternium-10 in Example 1 is 0.5 wt%. Compared with the concentrations of polyquaternium-10 in Examples 11-12, which are 0.05 wt% and 3.5 wt% respectively, the test accuracy of Example 1 is 91%, and no discoloration occurs after soaking for 1 minute. In contrast, the test accuracy of Examples 11-12 is only 81% and 80% respectively, and discoloration occurs after soaking for 1 minute. This indicates that the present application preferably controls the concentration of cationic organic salt within a reasonable range, which can better extend the soaking time of pH test paper and achieve higher test accuracy.

[0135] (4) As can be seen from the combined examples 1 and 13, in Example 13, trimethylammonium bromide was used as a cationic organic salt, which is not a polymer. Compared with Example 1, its detection accuracy was significantly reduced to 79%, and obvious decolorization occurred after soaking for 1 minute. This shows that the present application can form a mesh protective film by using anionic organic salts of polymer materials and fix the pH color reagent inside, thereby improving the detection accuracy and the immersion resistance of the test paper.

[0136] (5) As can be seen from the combined examples 1 and 1-3, the use of nonionic cellulose or anionic salts not only fails to protect the pH colorimetric reagent, but also reduces the detection accuracy to below 78%. This indicates that the present application uses cationic salts to form a mesh protective film on the surface of the substrate, which can protect the pH colorimetric reagent and improve the detection accuracy at the same time.

[0137] This application illustrates its detailed features through the above embodiments, but it is not limited to these detailed features, meaning that this application does not necessarily rely on them for implementation. Those skilled in the art should understand that any improvements to this application, equivalent substitutions for selected technical features, additions of auxiliary technical features, and selection of specific methods all fall within the protection and disclosure scope of this application.

Claims

1. A pH test paper, characterized in that The pH test paper comprises a substrate and a reagent loading layer, which is arranged on the substrate; The reagent loading layer comprises a pH color developing agent and a cationic organic salt.

2. The pH test paper according to claim 1, characterized in that, The pH color developing agent has an anion group, and the cationic organic salt has an ionic bond with the anion group; And / or, the surface of the reagent loading layer has a reticular protective film formed by the cationic organic salt; And / or, the substrate has a cationic group, and the pH color developing agent forms a cross-linking system with the cationic group on the substrate.

3. The pH test paper according to claim 2, characterized in that The thickness of the reticular protective film is 0.2-2 μm.

4. The pH test paper according to any one of claims 1 to 3, characterized in that The cationic organic salt is a cationic high-molecular organic salt; The cationic organic salt comprises any one or a combination of at least two of polyquaternary ammonium salt, cationic polyacrylamide, chitosan or polydimethyl diallyl ammonium chloride.

5. The pH test paper according to claim 4, characterized in that The polyquaternary ammonium salt comprises any one or a combination of at least two of polyquaternary ammonium salt-10, polyquaternary ammonium salt-9, polyquaternary ammonium salt-14 or polyquaternary ammonium salt-17; And / or, the weight average molecular weight of the cationic polyacrylamide is 60,000-1,200,000; And / or, the weight average molecular weight of the chitosan is 500,000-5,000,000; And / or, the weight average molecular weight of the polydimethyl diallyl ammonium chloride is 1,000,000-5,000,000.

6. The pH test paper according to claim 1, characterized in that The pH color developing agent comprises an anion indicator; and the anion indicator is an anionic dye molecule.

7. The pH test paper according to any one of claims 1 to 3, characterized in that The loading density of the reagent loading layer on the pH test paper is 1.5-10 mg / cm 3 .

8. A method for producing the pH test paper according to any one of claims 1 to 7, characterized by, The preparation method comprises: mixing the substrate and a solution containing the pH color developing agent, and then performing a first drying to obtain a first material; and then mixing the first material and a solution containing the cationic organic salt, and performing a second drying to obtain the pH test paper.

9. The method of preparing a pH test paper according to claim 8, characterized in that, The concentration of the pH color developing agent in the solution containing the pH color developing agent is 0.25-1.5 mM; And / or, the solvent in the solution containing the pH color developing agent comprises ethanol and water, and the volume ratio of ethanol to water is 0.25:1-9:1; And / or, the concentration of the cationic organic salt in the solution containing the cationic organic salt is 0.1-3.0 wt%.

10. Use of the pH test paper according to any one of claims 1-7 in pH detection.

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