A humic acid-resistant polymer membrane ion-selective electrode, its preparation and application

Abstract

This invention belongs to the field of potentiometric antifouling sensors, specifically relating to a humic acid-resistant polymer membrane ion-selective electrode, its preparation, and its application. The selective electrode consists of a polymer sensitive membrane and a protective layer sequentially adhered to the bottom of an electrode substrate; the protective layer is a polyvinylidene fluoride (PVDF) coating. This invention utilizes the low surface energy, high electronegativity, and dense film formation properties of the PVDF coating to reduce the wetting and adhesion of humic acid on the electrode membrane surface, while effectively preventing it from penetrating the polymer membrane, thereby improving the stability and service life of the polymer membrane ion-selective electrode in complex aquatic environments.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of potential type anti-fouling sensor, and particularly relates to a humic acid interference resistant polymer membrane ion selective electrode and preparation and application thereof. BACKGROUND

[0002] As a common electrochemical sensor, the polymer membrane ion selective electrode has been widely applied in environmental analysis due to its simple operation, fast detection speed, continuous detection and no influence of sample color and turbidity. Among them, humic acid as a common dissolved organic matter widely exists in environmental water such as river water and seawater, and soil and sediment. The environmental humic acid causes great challenge to the application of the polymer membrane ion selective electrode in complex environmental samples.

[0003] At present, the sensitive film of the polymer membrane ion selective electrode is generally composed of a polymer matrix material, a plasticizer, an ion carrier and an ion exchanger. The polymer matrix is mainly a hydrophobic material such as polyvinyl chloride, and the plasticizer is also easily dissolved in an organic reagent, which makes the surface of the electrode sensitive film lipophilic. This causes the dissolved humic acid in the detection solution to adhere to the surface of the electrode sensitive film through hydrophobic interaction, and enter the inside of the sensitive film through extraction, thereby changing the composition of the sensitive film. The above reasons will affect the thermodynamic response of the electrode, resulting in unstable electrode response, decreased detection performance and greatly shortened service life. At present, the humic acid in the sample is usually removed by pretreatment to reduce its influence on the polymer membrane ion selective electrode, and the research on how to improve the humic acid resistance of the electrode during in-situ detection in complex environments has not been reported. SUMMARY

[0004] The application aims to provide a humic acid interference resistant polymer membrane ion selective electrode and preparation and application thereof.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows:

[0006] A humic acid interference resistant polymer membrane ion selective electrode, the selective electrode is sequentially adhered with a polymer sensitive film and a protective layer on the bottom of an electrode substrate; wherein the protective layer is a polyvinylidene fluoride coating.

[0007] A conductive layer can be further arranged between the substrate and the polymer sensitive film.

[0008] The conventional electrode substrate can be a glassy carbon electrode, a gold electrode or a platinum electrode, etc.

[0009] The polyvinylidene fluoride coating is formed by dissolving polyvinylidene fluoride in N,N-dimethylformamide solution and coating on the surface of the electrode base polymer membrane; wherein the concentration of polyvinylidene fluoride in the solution is 2%-10% by mass percentage; the N,N-dimethylformamide solution is a mixture of N,N-dimethylformamide and tetrahydrofuran with a volume ratio of 1:0-1:1.

[0010] A preparation method of the anti-humic acid interference polymer membrane ion selective electrode, wherein a solution containing polyvinylidene fluoride is drop-coated on the surface of the sensitive membrane of the polymer membrane ion selective electrode to form a polyvinylidene fluoride coating.

[0011] The polymer membrane ion selective electrode is a solid contact polymer sensitive membrane cation / anion selective electrode or a liquid contact polymer sensitive membrane cation / anion selective electrode containing a polymer sensitive membrane.

[0012] The solution containing polyvinylidene fluoride is dried on the surface of the sensitive membrane of the polymer membrane ion selective electrode for 10-15 minutes, and then the electrode is immersed in deionized water to keep the polyvinylidene fluoride coating moist, thereby obtaining the anti-humic acid interference polymer membrane ion selective electrode.

[0013] The polyvinylidene fluoride coating is formed by dissolving polyvinylidene fluoride in N,N-dimethylformamide solution and coating on the surface of the electrode base polymer membrane; wherein the concentration of polyvinylidene fluoride in the solution is 2%-10% by mass percentage; the N,N-dimethylformamide solution is a mixture of N,N-dimethylformamide and tetrahydrofuran with a volume ratio of 1:0-1:1.

[0014] The polymer sensitive membrane is composed of an ion selective carrier, a lipophilic ion exchanger, a membrane base material, and a plasticizer in a weight ratio of 0.2-10:0.1-5:20-40:40-80.

[0015] The membrane base material includes but is not limited to polyvinyl chloride, polyurethane, silicone rubber, acetate fiber, polyacrylamide, or polymethyl methacrylate-dimethylaminoethyl methacrylate; the plasticizer includes but is not limited to o-nitrophenyl octyl ether, dioctyl phthalate, dibutyl phthalate, diisobutyl phthalate, dioctyl adipate, or dioctyl sebacate; the ion selective carrier includes but is not limited to lead ion, copper ion, iron ion, chromium ion, sodium ion, potassium ion, ammonium ion, calcium ion, magnesium ion, carbonate ion, nitrate ion, chloride ion, or bromide ion; and the lipophilic ion exchanger includes but is not limited to sodium tetrakis(3,5-di(trifluoromethyl)phenyl)borate or tridodecylammonium chloride.

[0016] The anti-humic acid interference polymer membrane ion selective electrode is applied in the detection of environmental water bodies against humic acid interference.

[0017] The anti-humic acid interference polymer membrane ion selective electrode can be applied to the analysis of environmental water bodies including lake water, river water or seawater, and reduces the influence of humic acid in the water body on the detection signal and service life of the electrode.

[0018] Principle: The polyvinylidene coating is modified on the surface of the polymer membrane ion selective electrode film, and the electrode is endowed with the anti-humic acid interference ability by virtue of the low surface energy, strong electronegativity, dense film formation and other characteristics of the polyvinylidene. Further, the low surface energy of the polyvinylidene reduces the infiltration and adhesion of the soluble humic acid molecules with hydrophobic skeleton and amphiphilic surface groups on the electrode surface. At the same time, the polyvinylidene has strong electronegativity due to the C-F bond, and the charge repulsion is generated with the electronegative groups such as phenolic hydroxyl and carboxyl on the surface of humic acid, further reducing the adhesion of humic acid. On the other hand, as a semi-crystalline polymer, the polyvinylidene can form a continuous and dense protective layer on the surface of the polymer membrane, thereby effectively preventing humic acid from entering the inside of the polymer membrane. In addition, the polyvinylidene itself does not contain ion exchange sites, and will not affect the normal response of the electrode. Therefore, the polyvinylidene coating can effectively improve the protection ability of the electrode against humic acid in the detection of environmental samples.

[0019] The present application has the advantages that:

[0020] 1. The present application uses polyvinylidene coating to modify the polymer membrane ion selective electrode, thereby improving the anti-humic acid interference ability of the polymer membrane ion selective electrode in the detection of environmental samples.

[0021] 2. The anti-humic acid interference polymer membrane ion selective electrode based on the polyvinylidene coating adopts a drop coating method to construct a protective coating on the surface of the electrode film, and the process is simple and does not affect the detection performance of the electrode.

[0022] 3. The polyvinylidene coating in the anti-humic acid interference ion selective electrode based on the polyvinylidene coating has universality for polymer membrane potential type sensors, and can be used to improve the anti-humic acid interference ability of polymer membrane ion selective electrodes containing different membrane matrix materials and different ion carrier types.

[0023] 4. The present application proposes a polymer membrane potential type anti-fouling sensor which can be applied to various environmental water bodies or samples containing humic acid. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The anti-humic acid interference polymer membrane ion selective electrode based on the polyvinylidene coating provided by the present application is shown in the structure diagram.

[0025] Figure 2 The anti-humic acid interference polymer membrane ion selective electrode based on the polyvinylidene coating provided by the present application is shown in the structure diagram. Figure 1Partial magnified electron microscope picture of the middle protective layer (polyvinylidene fluoride coating).

[0026] Figure 3 Comparison chart of the response of the unmodified and polyvinylidene fluoride modified polymer film chloride ion selective electrode to different concentrations of chloride ions provided by the embodiment of the present application; wherein A is the electrode potential response in a concentration range of 1.0*10 -7 ~1.0*10 -1 M sodium chloride solution, B is the electrode potential-chloride ion activity logarithmic value correction curve.

[0027] Figure 4 Potential drift and physical picture of the unmodified and polyvinylidene fluoride modified polymer film chloride ion selective electrode in humic acid solution provided by the embodiment of the present application; wherein A is the electrode potential drift in humic acid solution, B is the electrode surface physical picture before and after contacting humic acid and after removing the modified layer.

[0028] Figure 5 Comparison chart of the response of the unmodified and polyvinylidene fluoride modified polymer film chloride ion selective electrode to different concentrations of chloride ions provided by the embodiment of the present application; wherein A is the electrode potential response in a concentration range of 1.0*10 -7 ~1.0*10 -1 M sodium chloride solution, B is the electrode potential-chloride ion activity logarithmic value correction curve.

[0029] Figure 6 Potential response chart of the polymer film chloride ion selective electrode based on perfluorosulfonic acid resin coating in a concentration range of 1.0*10 -7 ~1.0*10 -1 M sodium chloride solution provided by the comparative example 1 of the present application.

[0030] Figure 7 Potential drift chart of the polymer film chloride ion selective electrode prepared by the modification method provided by the comparative example 2 and the comparative example 3 in humic acid solution; wherein PVDF is the electrode modified by the polyvinylidene fluoride coating provided by the embodiment of the present application, PDA is the electrode modified by the polydopamine coating provided by the comparative example 2, PVC-DMF is the electrode modified by the polyvinyl chloride-N,N dimethylformamide coating provided by step a of the comparative example 3, and PVC-DOS is the electrode modified by the polyvinyl chloride-decanedioic acid dioctyl ester coating provided by step b of the comparative example 3. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application are further described below in conjunction with examples, which are only for the purpose of illustrating and explaining the present application, and are not limited to the present application.

[0032] Example 1

[0033] Preparation of polymeric membrane chloride ion selective electrode based on polyvinylidene fluoride coating:

[0034] a. Preparation of chloride ion selective sensitive membrane solution: 360 mg of membrane components, including 2.0 wt% chloride ion carrier III, 33.0 wt% polyvinyl chloride particles, 63.8 wt% dioctyl sebacate and 1.2 wt% tridodecylammonium chloride, were weighed and added to 3.6 mL of tetrahydrofuran solution. After complete dissolution, a chloride ion selective electrode sensitive membrane solution was obtained.

[0035] b. Preparation of polymeric membrane chloride ion selective electrode based on polyvinylidene fluoride coating: 100 μL of electrode sensitive membrane solution was uniformly coated on the surface of a glassy carbon electrode containing a conductive layer (in this embodiment, a nickel-cobalt sulfide compound was used as the conductive layer), and was allowed to volatilize at room temperature for 12 h to obtain a polymeric membrane chloride ion selective electrode. 100 mg of polyvinylidene fluoride particles were dissolved in 2 mL of a solution of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, and after uniform dissolution, a polyvinylidene fluoride solution was obtained. 10 μL of the polyvinylidene fluoride solution was drop-coated to cover the surface of the electrode sensitive membrane, and was allowed to dry at room temperature for 15 min to form a polyvinylidene fluoride coating. Then, the electrode was immersed in 10 mL of M sodium chloride solution to keep the polyvinylidene fluoride coating moist, and a polymeric membrane chloride ion selective electrode modified with a polyvinylidene fluoride coating was prepared, which had a structure as shown in -3 Figure 1 and Figure 2 .

[0036] Example 2

[0037] Taking the detection of chloride ions as an example, the polymeric membrane chloride ion selective electrode modified with a polyvinylidene fluoride coating obtained in Example 1 (at the same time, a polymeric membrane chloride ion selective electrode without modification of a polyvinylidene fluoride coating prepared according to Example 1 was used as a control) was used as a working electrode, and an Ag / AgCl electrode was used as a reference electrode, and the potential of chloride ions in a 1.0 × 10 -7 ~1.0 × 10 -1 M sodium chloride solution was detected (see Figure 3 ).

[0038] The test results are shown in Figure 3 . After correction, the electrode before and after modification had a potential range of 9.9 × 10 -5 ~7.5 × 10 -2 ​The response of the M chloride ion exhibits a linear response within the activity range. The response slope of the unmodified electrode is -58.6 mV / decade, while that of the modified electrode is -60.0 mV / decade. This is close to the theoretical slope calculated based on the Nernst equation. Furthermore, the response of the electrode remains essentially unchanged before and after the modification with the polyvinylidene fluoride coating, demonstrating that the modification with the polyvinylidene fluoride coating does not affect the response performance of the electrode.

[0039] Example 3

[0040] Antifouling performance tests were conducted using the unmodified polyvinylidene fluoride (PVDF) coated polymer film chloride ion selective electrode and the PVDF-coated polymer film chloride ion selective electrode obtained in Example 1, respectively. Specifically:

[0041] The electrodes obtained in Example 1 were inserted into a solution containing 10 mg / L humic acid. -3 The electrode was immersed in sodium chloride (M) for 1 hour, and the potential change of the electrode was recorded using the method in Example 2. The results are as follows: Figure 4 As shown.

[0042] Depend on Figure 4 It is evident that after contact with humic acid, the potential of the unmodified electrode drops sharply, and the color of the polymer film darkens significantly, indicating that humic acid has entered the membrane through extraction. In contrast, the potential of the electrode modified with polyvinylidene fluoride (PVDF) coating remains stable. Although the color of the PVDF coating darkens, the polymer film remains colorless and transparent after the coating is removed. This demonstrates that the PVDF coating effectively blocks the contact between humic acid and the polymer film substrate, reduces potential drift when the electrode contacts humic acid, and ensures the stability of the potential response.

[0043] The electrode was then removed and rinsed with deionized water. The electrode was tested for concentrations in the range of 1.0 × 10⁻⁶. -7 ~1.0×10 -1 Chloride ion response in sodium chloride solution (see [reference]) Figure 5 The result is as follows: Figure 5 As shown, after contact with humic acid, at 9.9 × 10 -5 ~7.5×10 - 2 Within the chloride ion activity range of M, the slope of the calibration curve for the unmodified electrode dropped sharply from -58.6 mV / decade before contact to -50.7 mV / decade, indicating a decrease in electrode sensitivity. In contrast, the electrode modified with polyvinylidene fluoride coating still exhibited a good response to chloride ions, with the response slope shown in the calibration curve remaining at -57.3 mV / decade. This demonstrates that the surface of the electrode sensitive film modified with polyvinylidene fluoride coating effectively improved the electrode performance.

[0044] Example 4

[0045] Preparation of polymer membrane carbonate ion selective electrode based on polyvinylidene fluoride coating

[0046] a. Preparation of carbonate ion selective sensitive membrane solution: 360 mg of membrane components were weighed, including 5.10 wt% of carbonate ion carrier VII, 36.98 wt% of polyvinyl chloride, 56.78 wt% of dioctyl adipate, and 1.23 wt% of tridodecylammonium chloride, and were added to 3.6 mL of tetrahydrofuran solution. After complete dissolution, a carbonate ion selective electrode sensitive membrane solution was obtained.

[0047] b. Preparation of carbonate ion selective electrode based on polyvinylidene fluoride coating: 100 μL of the carbonate ion selective sensitive membrane solution was uniformly coated on the surface of a glassy carbon electrode containing a conductive layer (the conductive layer used in this example was a nickel-cobalt sulfide compound), and was allowed to evaporate at room temperature for 12 h to obtain a polymer membrane carbonate ion selective electrode. 100 mg of polyvinylidene fluoride particles were dissolved in 2 mL of a solution of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, and after uniform dissolution, a polyvinylidene fluoride solution was obtained. 10 μL of the polyvinylidene fluoride solution was drop-coated to cover the surface of the electrode sensitive membrane, and was dried at room temperature for 15 min to form a polyvinylidene fluoride coating. Then, the electrode was immersed in a solution containing 10 mg / L of humic acid in a buffer solution with a pH value of 8.0 and 0.1 M of tris-hydroxymethyl aminomethane hydrochloride and hydrochloric acid, and was kept in the solution for 1 d. After the electrode was taken out and washed with deionized water, the electrode was tested for response to carbonate ions in a solution with a concentration range of 5 × 10 -3 M sodium carbonate, with a background of a buffer solution of pH value 8.0, 0.1 M tris-hydroxymethyl aminomethane hydrochloride and hydrochloric acid, to keep the polyvinylidene fluoride coating moist, to obtain a polyvinylidene fluoride coating modified polymer membrane carbonate ion selective electrode.

[0048] c. The electrode obtained in step b was inserted into a solution containing 10 mg / L of humic acid in a buffer solution with a pH value of 8.0, 0.1 M tris-hydroxymethyl aminomethane hydrochloride and hydrochloric acid, and was kept in the solution for 1 d. After the electrode was taken out and washed with deionized water, the electrode was tested for response to carbonate ions in a solution with a concentration range of 5 × 10 -3 M sodium carbonate, with a background of a buffer solution of pH value 8.0, 0.1 M tris-hydroxymethyl aminomethane hydrochloride and hydrochloric acid, to keep the polyvinylidene fluoride coating moist, to obtain a polyvinylidene fluoride coating modified polymer membrane carbonate ion selective electrode. -2 ~1×10 -6 M carbonate ions (the solution background was the above-mentioned buffer solution). After contacting with humic acid, the polyvinylidene fluoride coating modified electrode still maintained good response to carbonate ions.

[0049] Comparative Example 1

[0050] Preparation and detection of polymer membrane chloride ion selective electrode based on perfluorosulfonic acid resin coating

[0051] a. Preparation of the chloride ion selective electrode based on the coating of perfluorosulfonic acid resin: the polymer membrane chloride ion selective electrode obtained in Example 1 was used. 0.2 mL of 5 wt% perfluorosulfonic acid resin was dissolved in 0.8 mL of anhydrous ethanol and ultrasonicated for 20 min to prepare a 1 wt% perfluorosulfonic acid resin solution. 20 μL of the perfluorosulfonic acid resin solution was dropped onto the surface of the electrode sensitive membrane and dried at room temperature for 15 min to form a perfluorosulfonic acid resin coating. Then the electrode was immersed in 10 mM NaCl solution to keep the perfluorosulfonic acid resin coating moist, thus obtaining the polymer membrane chloride ion selective electrode modified by the perfluorosulfonic acid resin coating. -3 M NaCl solution to keep the perfluorosulfonic acid resin coating moist, thus obtaining the polymer membrane chloride ion selective electrode modified by the perfluorosulfonic acid resin coating.

[0052] b. The potential response of the modified electrode obtained in step a was detected in the concentration range of 1.0 x 10 -7 ~1.0 x 10 -1 M NaCl solution was detected by the method in Example 2. The test results are shown in Table 2. Figure 6 As shown in Table 2, the chloride ion electrode modified by the perfluorosulfonic acid resin coating has lost the Nernst response and even shows a response trend of a cation electrode, indicating that the perfluorosulfonic acid resin seriously affects the normal response of the electrode.

[0053] Perfluorosulfonic acid resin is a commonly used anti-fouling material in the research of electrochemical sensors, but it is a cation exchanger itself and has ion exchange sites, which will introduce a large amount of cations in the solution to the surface of the polymer membrane, interfering with the normal response of the electrode to chloride ions. Therefore, the perfluorosulfonic acid resin coating is not suitable for the construction of the polymer membrane ion selective electrode for resisting humic acid interference in the present application.

[0054] Comparative Example 2

[0055] Preparation and detection of the polymer membrane chloride ion selective electrode based on the coating of polydopamine:

[0056] a. Preparation of the chloride ion selective electrode based on the coating of polydopamine: the polymer membrane chloride ion selective electrode obtained in Example 1 was used. The electrode was immersed in a buffer solution of 10 mM tris-hydroxymethyl aminomethane hydrochloride and hydrochloric acid with a background pH of 8.5 and containing 20 mg / mL dopamine for 12 h, thus obtaining the polymer membrane chloride ion selective electrode modified by the polydopamine coating.

[0057] b. The potential response of the modified electrode obtained in step a was detected in the concentration range of 1.0 x 10 -7 ~1.0 x 10 -1 M NaCl solution was detected by the method in Example 2. The test results are shown in Table 2.

[0058] c. The modified electrode obtained in step a was inserted into 10 mL of 10 mg / L humic acid solution -3 M sodium chloride solution, and the potential change of the electrode when it contacted with humic acid was recorded by the method of Example 2, and the results are shown in Table 1. Figure 7 After contacting with humic acid, the potential of the electrode modified by the polydopamine coating decreased slowly compared with the polyvinylidene fluoride coating used in the example, indicating that the coating had a certain blocking effect on humic acid, but could not completely prevent the influence of humic acid on the electrode.

[0059] Polydopamine is widely used as an antifouling modification material due to its hydrophilicity and electronegativity, but the formed coating has a cross-linked network structure and a thickness of only a few hundred nanometers, which is difficult to completely block the passage of macromolecules such as polyions and humic acid. At the same time, polydopamine has phenolic hydroxyl groups, which can interact with anion exchangers such as tridodecylammonium chloride in polymer membranes. Therefore, the polydopamine coating is not suitable for the construction of polymer membrane ion-selective electrodes for resisting humic acid interference in the present application.

[0060] Comparative Example 3

[0061] Preparation and detection of a polymer membrane chloride ion-selective electrode based on a polyvinyl chloride coating:

[0062] a. Preparation of a chloride ion-selective electrode based on a polyvinyl chloride-N,N dimethylformamide coating: using the polymer membrane chloride ion-selective electrode obtained in Example 1, and referring to the preparation of the polyvinylidene fluoride coating in Example 1, polyvinylidene fluoride particles were replaced with polyvinyl chloride powder. 100 mg of polyvinyl chloride powder was dissolved in a 2 mL solution of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:1, and a polyvinyl chloride-N,N dimethylformamide solution was obtained after uniform dissolution. 10 μL of the solution was drop-coated to cover the surface of the electrode sensitive membrane, and dried at room temperature for 15 min to form a coating. Then the electrode was immersed in 10 mL of 10 mg / L humic acid solution, and the potential change of the electrode when it contacted with humic acid was recorded by the method of Example 2, and the results are shown in Table 1. -3 M sodium chloride solution, and the potential change of the electrode when it contacted with humic acid was recorded by the method of Example 2, and the results are shown in Table 1.

[0063] b. Preparation of a chloride ion-selective electrode based on a polyvinyl chloride-decanedioic acid dioctyl ester coating: referring to step a, N,N-dimethylformamide was replaced with the plasticizer decanedioic acid dioctyl ester, and a polymer membrane chloride ion-selective electrode modified by a polyvinyl chloride-decanedioic acid dioctyl ester coating was prepared.

[0064] c. The modified electrode obtained in step a was inserted into 10 mL of 10 mg / L humic acid solution -7 ~1.0×10 -1The potential response in M NaCl solution. The response slope of the two modified electrodes is close to the theoretical slope, which proves that the PVC coating does not affect the response performance of the electrode.

[0065] d. The modified electrode obtained by steps a, b is inserted into 10 mL of 10 mg / L humic acid solution -3 M NaCl solution. The potential change of the electrode when it contacts with humic acid is recorded by the method of Example 2. The results are shown in Table 2. Figure 7 .

[0066] After contacting with humic acid, the potential of the electrode modified by PVC-N,N-dimethylformamide coating slowly decreases, which indicates that the coating has a certain protective effect on humic acid, but cannot completely block the influence of humic acid on the electrode. PVC is a high molecular polymer similar in structure to polyvinylidene fluoride, which is also the matrix material of polymer membrane. Although it has certain hydrophobicity and electronegativity, PVC is an amorphous polymer, and dissolving in N,N-dimethylformamide cannot make it form a dense protective coating, so it cannot effectively protect the electrode from the interference of humic acid.

[0067] Therefore, step b uses the plasticizer dioctyl sebacate to replace N,N-dimethylformamide, and the electrode is modified by PVC-dioctyl sebacate coating. After contacting with humic acid, the potential of the electrode modified by PVC-dioctyl sebacate coating decreases sharply, which indicates that the coating cannot effectively protect the electrode from the interference of humic acid. Plasticizers can help PVC form a continuous coating, however, the composition of the coating is close to that of the polymer membrane, which causes the effective components of the polymer membrane, ion carriers and ion exchangers, to be extracted into the coating, which leads to direct contact between humic acid and the effective components of the polymer membrane, causing significant potential drift. Therefore, PVC-dioctyl sebacate coating is not suitable for the construction of the polymer membrane ion-selective electrode against humic acid interference in the present application.

Claims

1. A polymeric membrane ion-selective electrode resistant to humic acid interference, characterized in that: The selective electrode is sequentially adhered with a polymer sensitive film and a protective layer at the bottom of the electrode substrate; wherein the protective layer is a polyvinylidene fluoride coating. The polyvinylidene fluoride coating is obtained by dissolving polyvinylidene fluoride in an N,N-dimethylformamide solution and coating the surface of the electrode substrate polymer film; wherein the concentration of polyvinylidene fluoride in the solution is 2-10% by mass percentage; and the volume ratio of N,N-dimethylformamide to tetrahydrofuran in the N,N-dimethylformamide solution is 1:0-1:

1.

2. The humic acid interference resistant polymeric membrane ion-selective electrode according to claim 1, wherein: A conductive layer is arranged between the substrate and the polymer sensitive film.

3. A method for the preparation of a polymeric membrane ion-selective electrode resistant to humic acid interference according to claim 1, characterized by the fact that: A solution containing polyvinylidene fluoride is drop-coated on the surface of the polymer membrane ion-selective electrode sensitive film to form a polyvinylidene fluoride coating; wherein the polymer membrane ion-selective electrode is a solid contact type cation / anion selective electrode containing a polymer sensitive film or a liquid contact type polymer sensitive film cation / anion selective electrode.

4. The method for preparing a humic acid interference resistant polymeric membrane ion selective electrode according to claim 3, characterized in that: The solution containing polyvinylidene fluoride is dried on the surface of the polymer membrane ion-selective electrode sensitive film for 10-15 minutes, and then the electrode is immersed in deionized water to keep the polyvinylidene fluoride coating moist, thereby obtaining a humic acid interference-resistant polymer membrane ion-selective electrode.

5. The method for preparing a humic acid interference resistant polymeric membrane ion-selective electrode according to claim 3 or 4, characterized in that: The polyvinylidene fluoride coating is obtained by dissolving polyvinylidene fluoride in an N,N-dimethylformamide solution and coating the surface of the electrode substrate polymer film; wherein the concentration of polyvinylidene fluoride in the solution is 2-10% by mass percentage; and the volume ratio of N,N-dimethylformamide to tetrahydrofuran in the N,N-dimethylformamide solution is 1:0-1:

1.

6. Use of the polymeric membrane ion-selective electrode according to claim 1, characterized in that: The polymer membrane ion-selective electrode is used in the detection of humic acid interference in environmental water bodies.

Images