CN114019005B - High-precision electrochemical detection method for polymer sensitive film based on ion migration amplification effect - Google Patents

High-precision electrochemical detection method for polymer sensitive film based on ion migration amplification effect Download PDF

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CN114019005B
CN114019005B CN202111222228.1A CN202111222228A CN114019005B CN 114019005 B CN114019005 B CN 114019005B CN 202111222228 A CN202111222228 A CN 202111222228A CN 114019005 B CN114019005 B CN 114019005B
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江天甲
秦伟
刘鲁
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Yantai Institute of Coastal Zone Research of CAS
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    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract

The invention relates to a high-precision detection method of a potential type sensor (polymer film ion selective electrode), in particular to a high-precision electrochemical detection method of a polymer sensitive film based on an ion migration amplification effect. The polymer film ion selective electrode is used as a recognition element, the ion transfer electrode is used as a signal conversion element, and the potential change of the polymer film ion selective electrode is used for driving the migration of the indication ions in the cavity of the ion transfer electrode across the electrode film, so that the concentration information of the ions to be detected is converted into an analysis signal which is more sensitive than the potential signal, and the high-precision quantitative detection of the target in the detection liquid is realized. The method has certain universality, and can realize detection of different target objects by changing the types of the indication ions.

Description

High-precision electrochemical detection method for polymer sensitive film based on ion migration amplification effect
Technical Field
The invention relates to a high-precision detection method of a potential type sensor (polymer film ion selective electrode), in particular to a high-precision electrochemical detection method of a polymer sensitive film based on an ion migration amplification effect.
Background
Ion selective electrodes are an important branch of chemical sensors and have been widely used for direct measurement of ions in a variety of environmental samples. It should be noted that, although polymer membrane ion selective electrode technology has undergone tremendous development in recent years, quantitative analysis is limited by the Nernst equation because the traditional polymer membrane ion selective electrode response is based on thermodynamic equilibrium state, with zero current open circuit potential being its dominant signal output mode.According to the theory of ion selective electrode response, the potential change generated by each order of magnitude of change of the ion activity at normal temperature and pressure is about 59/n mV (n is the charge number of the ion to be detected), which leads the electrode to change the micro-activity of the ion to be detected (lower than 10 -2 An order of magnitude) is extremely low in response sensitivity. Therefore, the conventional zero-current open circuit potential detection mode is difficult to meet the detection requirement of high-precision analysis.
In the existing research on improving the detection precision of the ion selective electrode of the traditional polymer membrane, the main research content is the research of a constant potential coulometry analysis method based on redox capacitance. In such transduction methods, a solid contact ion selective electrode is generally used as a working electrode, a corresponding decaying current is generated by using the redox reaction of an ion-electron transduction layer, and then the obtained current-time curve is integrated to obtain the total charge quantity, wherein the charge quantity is related to the activity or concentration change of ions to be detected in a sample. It should be noted that the signal conversion element in these studies is an ion-electron conversion layer, and the detection sensitivity of the sensor depends on the capacitance property of the material of the ion-electron conversion layer, but the types of ideal capacitance materials currently available for preparing the conversion layer are very limited. In addition, the method has the problems that the controllable adjustment of the detection precision of the electrode cannot be realized, the detection stability of the electrode is easily influenced by the formation of a water layer, and the like.
Disclosure of Invention
The invention aims to provide a high-precision electrochemical detection method of a polymer sensitive film based on an ion migration amplification effect.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a high-precision electrochemical detection method of a polymer sensitive film based on an ion migration amplification effect uses a polymer film ion selective electrode as a recognition element, uses an ion migration electrode as a signal conversion element, and utilizes the potential change of the polymer film ion selective electrode to drive the migration of indication ions in an ion migration electrode cavity to cross the electrode film, so that the concentration information of ions to be detected is converted into an analysis signal which is more sensitive than a potential signal, and the high-precision quantitative detection of a target in detection liquid is realized.
The method is characterized in that a polymer membrane ion selective electrode is used as a reference electrode, an ion migration electrode is used as a working electrode, a three-electrode system of the working electrode, the reference electrode and a counter electrode is adopted, under constant potential control, the potential change of the reference electrode polymer membrane ion selective electrode caused by the concentration change of ions to be detected is utilized to drive the ions to migrate into or out of a membrane of the ion migration electrode cavity, so that the concentration information of the ions to be detected in a solution to be detected is converted into an analysis signal which is more sensitive than a potential signal, and the high-precision quantitative detection of the target in the detection solution is realized.
The polymer membrane ion selective electrode is an all-solid polymer membrane ion selective electrode without internal liquid filling or a liquid contact type ion selective electrode containing internal liquid filling; the polymer film ion-selective electrode is prepared by coating a polymer film on the surface of a polymer film ion-selective electrode substrate or adhering the polymer film on the bottom of an electrode cavity; for example, the ion selective electrode of the all-solid polymer film is prepared by coating the surface of a conductive substrate with a polymer film; the liquid contact ion selective electrode containing the internal liquid filling is prepared by sticking a polymer film on the bottom of an electrode cavity, and the internal liquid filling can be of concentration 10 -3 -1M KCl solution, naCl solution, caCl 2 Solution, mgCl 2 Solution, HCl solution, na 2 CO 3 The solution or 0.1-1000mM Tris-HCl buffer solution (pH 7.0-10.0) containing 1-1000mM NaCl.
The conductive substrate in the all-solid-state polymer film ion selective electrode is a disc electrode, an ITO conductive glass electrode, a screen printing electrode or a paper chip electrode; the polymer film is prepared by mixing an ion selective carrier of ions to be detected with a lipophilic ion exchanger according to a mass ratio of 1-2:1, and then according to a mass ratio of 1:2 adding the film matrix material and the plasticizer.
The ion transfer electrode is a liquid contact ion selective electrode containing an internal liquid filling; the bottom of the ion migration electrode is coated with an electrode sensitive film, and the electrode sensitive film is a liquid sensitive film or a solid sensitive film.
The internal liquid of the ion migration electrode is an aqueous solution containing indicating ions, the concentration of the indicating ions in the aqueous solution is 0.0000001-100M, and the indicating ions are all charged substances and have the same electrical property with the ions to be detected;
the liquid sensitive film is prepared by uniformly mixing a lipophilic ion exchanger and a plasticizer according to the mass ratio of 1:1-9;
the solid sensitive film is composed of 1-50% of lipophilic ion exchanger by mass, and the mass ratio of film base material to plasticizer is 1:2, mixing to obtain the product.
The counter electrode can be a platinum wire, a platinum sheet, a platinum disk electrode or a carbon-based electrode.
The detection target is potassium ion, sodium ion, calcium ion, magnesium ion, hydrogen ion, heavy metal ion, chloride ion, nitrate ion, carbonate ion, sulfate ion, phosphate ion, ammonia nitrogen, small organic molecule, protein, bacteria or cells.
The lipophilic ion exchanger is sodium tetrakis (3, 5-bis (trichloromethyl) phenyl) borate, potassium tetrakis (3, 5-bis (trichloromethyl) phenyl) borate or tri (dodecyl) methyl ammonium chloride;
the film matrix material is polyvinyl chloride, polyurethane, silicon rubber, acetate fiber, polyacrylamide or polymethyl methacrylate-dimethylaminoethyl methacrylate; the plasticizer is o-nitrophenyl octyl ether, dioctyl phthalate, dibutyl phthalate, diisobutyl phthalate, dioctyl adipate or dioctyl sebacate.
The ion selective carrier of the ion to be detected in the polymer film is that when the ion to be detected is K + In the case, the ion selective carrier is a potassium ion carrier I or III; when the ion to be measured is Na + In the case of sodium ion carrier I, II or III as the ion selective carrier; when the ion to be measured is Ca 2+ In the case, the ion selective carrier is a calcium ion carrier I, II, III or IV; when the ion to be measured is H + In the process, the ion selective carrier is a hydrogen ion carrier I; when the ion to be measured is CO 3 2- In the case, the ion selective carrier is carbonate ionophore I, II, III or IV; when the ion to be measured is Cu 2+ When the ion selective carrier is copper ion carrierI, a step of I; when the detected ion is another ion, an ion-selective carrier of the ion reported in the prior art can be used.
The detection method adopts a sample cell and a detection cell for separation, wherein a polymer membrane ion selective electrode contacted with a sample solution is placed in the sample cell and is used for sensing the activity change of ions to be detected in a sample; the ion migration electrode and the counter electrode are arranged in the detection cell and are used for converting potential signals of the polymer membrane ion selective electrode into current signals, and the two cells are connected through a salt bridge.
Principle of action: the electrochemical detection adopts a three-electrode system of a working electrode, a reference electrode and a counter electrode to detect ions to be detected in the detection solution with high precision. Wherein the polymer membrane ion selective electrode is a reference electrode; the ion transfer electrode is a working electrode. The reference electrode polymer membrane ion selective electrode is used as an identification element for contacting with a sample solution to sense the concentration change of a target object to be detected in the sample; the ion transfer electrode is used as a signal conversion element for converting the potential signal of the polymer film ion selective electrode into a current signal. The voltage between the reference electrode and the working electrode is kept constant by means of an electrochemical workstation. When the concentration of the target to be detected in the sample solution changes, the potential of the polymer membrane ion selective electrode changes. Since the voltage between the ion transfer electrode and the polymer membrane ion selective electrode is constant, the ion transfer electrode needs to generate a potential change with the same value while the potential of the polymer membrane ion selective electrode changes. Therefore, the indication ions in the ion transfer electrode cavity need to migrate in or out across the ion transfer electrode sensitive film through ion exchange action until the potential changes of the two electrode films are equal. Corresponding current can be generated in the process of indicating ion transmembrane migration, the total charge quantity generated in the process can be obtained by integrating the obtained current-time curve, and high-precision quantitative analysis is carried out by utilizing the mathematical relationship between the total charge quantity and the concentration of the target object to be detected.
The invention has the advantages that:
1. the high-precision electrochemical detection method of the polymer sensitive film based on the ion migration amplification effect adopts a detection mode different from the traditional zero-current open-circuit potential, and the method drives the indicated ions to migrate by means of the change of the film potential to generate a current signal so as to realize the conversion from the electrode potential signal to the high-sensitivity signal and effectively improve the detection precision of the polymer film ion selective electrode.
2. The high-precision electrochemical detection method of the polymer sensitive film based on the ion migration amplification effect can realize high-precision detection of the concentration change of a tiny object to be detected, wherein the tiny detection amount is 10 -3 -10 -2 M。
3. The high-precision electrochemical detection method for the polymer sensitive film based on the ion migration amplification effect has universality, and can realize high-precision analysis on various targets to be detected by changing the types of the indication ions and the lipophilic ion exchangers in the ion migration electrode sensitive film, so that the application range of the method is greatly expanded.
Drawings
FIG. 1 is a diagram showing the Ca-based structure according to example 1 of the present invention 2+ The high-precision electrochemical detection method of the polymer sensitive film with the ion migration amplification effect is used for the working principle schematic diagram of pH analysis.
FIG. 2 shows a polymer film H with an internal liquid filling according to example 2 of the present invention + The ion selective electrode responds to potential response signals of different pH values in a zero-current open-circuit potential detection mode; the left is a real-time response graph of the electrode to solutions with different pH values, and the right is a linear relation between the obtained potential signal and the different pH values.
FIG. 3 is a diagram showing Ca-based structure according to example 2 of the present invention 2+ The high-precision electrochemical detection method of the polymer sensitive film with the ion migration amplification effect is used for responding signals of different pH values; wherein, the left side is a coulomb response diagram of the electrode to solutions with different pH values, and the right side is a linear relation between the obtained coulomb signal and the different pH values.
Detailed Description
The following description of the embodiments of the present invention is further provided in connection with the accompanying examples, and it should be noted that the embodiments described herein are for the purpose of illustration and explanation only, and are not limiting of the invention.
The invention improves the precision of a polymer sensitive film in an electrochemical detection method based on an ion migration amplification effect, specifically uses a polymer film ion selective electrode as a recognition element, uses an ion migration electrode as a signal conversion element, utilizes the potential change of the polymer film ion selective electrode to drive the migration of indication ions in an ion migration electrode cavity to cross the electrode sensitive film, and generates a current signal, so that the concentration information of a target object to be detected is converted into an analysis signal which is more sensitive than the potential signal, and the detection precision of the polymer film ion selective electrode is obviously improved.
Example 1
Based on Ca 2+ The high-precision electrochemical detection method of the polymer sensitive film with the ion (indicator ion) migration amplification effect is used for pH analysis and comprises the following specific measurement steps:
a. polymer film H + Preparation of ion-selective sensitive membranes: polyvinyl chloride particles, o-nitrophenyl octyl ether, H + A mixture of ionophore I and sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate 360mg, in which 32.7% by weight of PVC particles, 65.6% by weight of o-nitrophenyl octyl ether, 1.1% by weight of H + Ionophore and 0.6wt% of sodium tetra (3, 5-bis (trifluoromethyl) phenyl) borate, transferring the mixture into 3.6mL of tetrahydrofuran solution, stirring for 6H to disperse uniformly to obtain H + Ion selective electrode sensitive membrane solution. Pouring the electrode sensitive film solution into a glass ring (with inner diameter of 3.6 cm) fixed on a glass plate, standing at room temperature for 8 hr, and evaporating solvent to obtain uniform H + Ion selective polymer sensitive membranes.
b. Polymer film H with internal liquid filling + Ion selective electrode preparation: the H obtained above is reacted with + The ion-selective polymer sensitive film was punched out with a punch to obtain a polymer sensitive film having a diameter of about 0.7cm, the punched film was fixed to the bottom of a polyvinyl chloride tube by tetrahydrofuran, a 0.1mM Tris-HCl buffer solution (pH 7.0) containing 10mM NaCl was injected into the electrode cavity as an internal liquid, and an Ag/AgCl electrode was inserted into the cavity as an internal conductive substrate.
c. Based onCa of liquid sensitive film 2+ Preparation of ion transfer electrode: 100mg of a mixture of o-nitrophenyl octyl ether and sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate, which is 10wt% of sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate and 90wt% of o-nitrophenyl octyl ether, is transferred into 1.0mL of tetrahydrofuran solution, and the mixture is stirred for 6 hours to be uniformly dispersed, so that the liquid electrode sensitive film solution is obtained. Fixing microporous polypropylene film with thickness of 25 μm and diameter of 0.7cm at bottom of polyvinyl chloride tube with tetrahydrofuran, dripping 8 μl of the prepared liquid electrode sensitive film solution onto polypropylene film surface, and making 1M Ca solution transparent 2 Cl solution is injected into the electrode cavity to be used as internal liquid, and the Ag/AgCl electrode is inserted into the cavity to be used as an internal conductive matrix.
determination of the pH: the polymer film H thus produced + The ion selective electrode is a reference electrode; ca based on liquid sensitive film 2+ The ion transfer electrode is a working electrode; the platinum wire electrode is a counter electrode. In order to overcome the influence of other components in the liquid phase on the detection signals of the constructed sensor system, a method for separating a sample cell from a detection cell is adopted, namely: placed in the sample cell is a polymer membrane H in contact with the sample solution + Ion selective electrode for sensing H in a sample + The activity of the ions changes; placed in the detection cell is Ca 2+ Ion transfer electrode and platinum wire electrode for H + The potential signal of the ion selective electrode was converted into a current signal, and the two cells were connected by a salt bridge (wherein the salt bridge was a 3M KCl agar solution prepared by uniformly mixing 100g deionized water, 6g agar powder, and 22.35g KCl) (see FIG. 1). Maintaining the voltage between the reference electrode and the working electrode constant by using an electrochemical workstation, and taking the sample as H in the liquid phase + When the ion concentration increases, the polymer film H + The membrane potential of the ion-selective electrode increases with it and tends to cause Ca 2+ Ca in the liquid filling in the cavity of ion transfer electrode 2+ Ion transport across the membrane is released to the detection cell such that the polymer membrane H + Ion-selective electrode and Ca 2+ The membrane potential changes of both ion transfer electrodes are equal. At Ca 2+ The ion migration-release process can generate corresponding current by the methodThe total charge generated in the process can be obtained by integrating the current-time curve, and the total charge and the H to be detected are utilized + The mathematical relationship between ion concentrations was used for high-precision pH quantitative analysis. Through the detection principle, the potential signal of the polymer film ion selective electrode in the traditional zero-current open-circuit electrode detection mode is converted into a current signal based on the ion migration amplification benefit, so that the signal amplification of the concentration change of the target ion to be detected is realized.
Example 2
To detect H + For example, the polymer film H obtained in example 1 was used + Ion-selective electrode and Ca 2+ The ion transfer electrode carries out high-precision detection on the pH value of the solution:
a. polymer film H prepared in example 1 + The ion-selective electrode is a reference electrode, ca 2+ The ion transfer electrode is a working electrode, the commercial platinum wire electrode is a counter electrode, and the ion transfer electrode is used for different concentrations of H + Detecting ions with high precision;
b. h obtained in example 1 + The ion-selective electrode was activated overnight in 0.1mM Tris-HCl buffer (pH 7.0) containing 10mM NaCl.
c. Ca based on liquid sensitive film obtained in example 1 2+ The ion transfer electrode is arranged in a detection cell (50 mL 10 is contained therein) -3 M Ca 2+ Solution), after activation H + The ion-selective electrode was placed in a sample cell (containing 10mL of 0.1M Tris-HCl buffer solution (pH 8.0)), and the detection cell and the sample cell were connected by a salt bridge.
d. 1M H configured with HCl + Ion stock solution, 10mL of 0.1M Tris-HCl buffer solution (pH 8.0) base solution in the sample cell was added with different volumes of H of the above-mentioned configuration + Ion stock solutions were obtained to give a series of base solutions with pH of 8.000, 7.999, 7.998, 7.997, 7.996, 7.995. H obtained in example 1 + The potential response of the ion-selective electrode to these base fluids and the relationship between the response signal and the different pH values in the zero-current open-circuit potential detection mode are shown in fig. 2. Electrochemical work station at Ca 2+ Ion transfer electrode and H + Ion selective electricityA constant voltage was applied between the poles and the current-time curve generated when the pH of the 0.1M Tris-HCl buffer solution in the sample cell was varied was recorded. The total charge generated in the process can be obtained by integrating the obtained current-time curve, and the mathematical relationship between the total charge and the pH of the solution in the sample cell is used for high-precision pH quantitative analysis, and the obtained experimental result is shown in FIG. 3.
As can be seen from FIG. 3, the high-precision electrochemical detection method of the invention can realize accurate detection of small pH change (8.000-7.995) and presents good response results. In the conventional zero current open circuit potential mode, a potential signal of about 0.057mV is generated by a 0.001pH unit change, with about 0.020mV noise (see FIG. 2 left); in the high-precision electrochemical detection mode of the present invention, the coulomb signal generated by the 0.001pH unit change is about 1.57 μc, while no significant noise interference is present (see fig. 3 left). Therefore, the high-precision electrochemical detection method provided by the invention has the advantages that the noise of the detection result is smaller, and the detection signal of 0.001pH unit is more obvious. In addition, the precision of the detection result obtained in the detection mode based on the ion migration amplification effect is 60 mu pH units, which is far smaller than the precision (about 2.46mpH units) in the traditional zero-current open-circuit potential detection mode (see right side of fig. 2 and right side of fig. 3), which shows that the electrochemical detection method of the polymer sensitive film based on the ion migration amplification effect can be used for realizing high-precision analysis of the target object to be detected in the solution.
Example 3
The indicator ion is chloride ion, the lipophilic ion exchanger is tri (dodecyl) methyl ammonium chloride, and the potential signal of the carbonate ion selective electrode is converted to realize the micro carbonate concentration change (less than 10) -2 M) high precision analysis, the specific measurement steps are as follows:
a. preparation of polymer film carbonate ion-selective sensitive film: 360mg of a mixture of polyvinyl chloride (PVC) particles, dioctyl adipate, a carbonate ion carrier VII and tri (dodecyl) methyl ammonium chloride, wherein the mixture comprises 31.3wt% of PVC particles, 62.7wt% of dioctyl adipate, 4.0wt% of carbonate ion carrier VII and 2.0wt% of tri (dodecyl) methyl ammonium chloride, and the mixture is transferred into 3.6mL of tetrahydrofuran solution and stirred for 6 hours to be uniformly dispersed, so that the carbonate ion selective electrode sensitive film solution is obtained. Pouring the electrode sensitive film solution into a glass ring (with the inner diameter of 3.6 cm) fixed on a glass plate, standing for 8 hours at normal temperature, and evaporating the solvent to obtain the uniform carbonate ion selective polymer sensitive film.
b. Preparation of a polymer film carbonate ion selective electrode with internal liquid filling: the polymer sensitive film obtained above was punched with a punch to obtain a polymer sensitive film having a diameter of about 0.7cm, and the punched film was fixed to the bottom of a polyvinyl chloride tube by tetrahydrofuran to obtain a film containing 0.1M Na 2 CO 3 And injecting 0.1M NaCl solution into the electrode cavity to serve as an internal liquid, and inserting an Ag/AgCl electrode into the cavity to serve as a built-in conductive matrix.
c. Preparation of a chloride ion transfer electrode based on a liquid sensitive film: 100mg of a mixture of dioctyl adipate and tri (dodecyl) methyl ammonium chloride, wherein 10wt% of tri (dodecyl) methyl ammonium chloride and 90wt% of dioctyl adipate are added into 1.0mL of tetrahydrofuran solution, and the mixture is stirred for 6h to be uniformly dispersed, so that the liquid electrode sensitive film solution is obtained. A microporous polypropylene film with the thickness of about 25 micrometers and the diameter of 0.7cm is fixed at the bottom of a polyvinyl chloride pipe through tetrahydrofuran, 8 mu L of the prepared liquid electrode sensitive film solution is dripped on the surface of the polypropylene film, 1M NaCl solution is injected into an electrode cavity to serve as internal liquid, and an Ag/AgCl electrode is inserted into the cavity to serve as an internal conductive matrix.
d. Determination of carbonate: the prepared polymer film carbonate ion selective electrode is used as a reference electrode, a chloride ion migration electrode based on a liquid sensitive film is used as a working electrode, and a platinum wire electrode is used as a counter electrode. In order to overcome the influence of other components in the liquid phase on the detection signals of the constructed sensor system, a method for separating a sample cell from a detection cell is adopted, namely: a polymer membrane carbonate ion selective electrode which is in contact with the sample solution is arranged in the sample cell and is used for sensing the activity change of carbonate ions in the sample; placed in the detection cell are chloride ion transfer electrode and platinum wire electrode for electrically connecting carbonate ion selective electrodeThe bit signal is converted into a current signal, and the two tanks are connected through a salt bridge (wherein the salt bridge is a 3M KCl agar solution and is prepared by uniformly mixing 100g of deionized water, 6g of agar powder and 22.35g of KCl). The electrochemical workstation is used for keeping the voltage between the reference electrode and the working electrode constant, when the concentration of carbonate ions in the test liquid phase is increased, the membrane potential of the polymer membrane carbonate ion selective electrode is reduced along with the increase of the concentration of carbonate ions, and chlorine ions in the liquid filling in the cavity of the chlorine ion transfer electrode are transferred and released to the detection pool through the membrane, so that the membrane potential change of the polymer membrane carbonate ion selective electrode and the chlorine ion transfer electrode is equal. Corresponding current can be generated in the chloridion migration-release process, the total charge quantity generated in the process can be obtained by integrating the obtained current-time curve, and the high-precision carbonate radical quantitative analysis can be carried out by utilizing the mathematical relationship between the total charge quantity and the concentration of carbonate radical ions to be detected, so that the method can realize the process of 10 -2 Accurate analysis of M carbonate concentration changes.
Example 4
The mobile ion is polycation protamine, the lipophilic ion exchanger is sodium tetra (3, 5-di (trifluoromethyl) phenyl) borate, and the ion exchange agent is a catalyst for H + The potential signal of the ion selective electrode is converted, so that high-precision analysis of tiny pH change (0.001 pH unit) in a sample can be realized.
The specific measurement steps are as follows:
a. polymer film H prepared in example 1 + The ion selective electrode is a reference electrode, the protamine ion migration electrode is a working electrode, the commercial platinum wire electrode is a counter electrode, and the ion selective electrode is used for different concentrations of H + Detecting ions with high precision;
b. preparation of a protamine ion transfer electrode based on a liquid sensitive membrane: 100mg of a mixture of o-nitrophenyl octyl ether and sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate, which is 10wt% of sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate and 90wt% of o-nitrophenyl octyl ether, is transferred into 1.0mL of tetrahydrofuran solution, and the mixture is stirred for 6 hours to be uniformly dispersed, so that the liquid electrode sensitive film solution is obtained. Passing a microporous polypropylene film having a thickness of about 25 microns and a diameter of 0.7cm through tetrahydrofuranFixing on the bottom of polyvinyl chloride tube, dripping 8 μl of the prepared liquid electrode sensitive film solution on the surface of polypropylene film, and adding 1mg mL of the film after the film becomes transparent -1 The protamine solution is injected into the electrode cavity as an internal liquid, and the Ag/AgCl electrode is inserted into the cavity as an internal conductive matrix.
determination of the pH: the polymer film H thus produced + The ion selective electrode is a reference electrode, the protamine ion migration electrode based on the liquid sensitive film is a working electrode, and the platinum wire electrode is a counter electrode. In order to overcome the influence of other components in the liquid phase on the detection signals of the constructed sensor system, a method for separating a sample cell from a detection cell is adopted, namely: placed in the sample cell is a polymer membrane H in contact with the sample solution + Ion selective electrode for sensing H in a sample + The activity of the ions changes; placed in the detection cell are protamine ion transfer electrode and platinum wire electrode for transferring H + The potential signal of the ion selective electrode was converted into a current signal, and the two cells were connected by a salt bridge (wherein the salt bridge was a 3M KCl agar solution prepared by uniformly mixing 100g deionized water, 6g agar powder, and 22.35g KCl) (see FIG. 1). Maintaining the voltage between the reference electrode and the working electrode constant by using an electrochemical workstation, and taking the sample as H in the liquid phase + When the ion concentration increases, the polymer film H + The membrane potential of the ion selective electrode is increased along with the increase, and the protamine ions in the liquid filling in the cavity of the protamine ion migration electrode are gradually migrated and released to the detection pool through the membrane, so that the polymer membrane H + The membrane potential changes of both the ion selective electrode and the protamine ion transfer electrode are equal. The corresponding current can be generated in the migration-release process of protamine ions, the total charge quantity generated in the process can be obtained by integrating the obtained current-time curve, and the total charge quantity and H to be detected are utilized + The mathematical relationship between ion concentrations is used for high-precision pH quantitative analysis, so that accurate analysis of 0.001pH unit change can be realized.

Claims (3)

1. A method for electrochemically detecting a target object with high precision based on a polymer sensitive film of an ion migration amplification effect is characterized by comprising the following steps: the method comprises the steps of taking a polymer film ion selective electrode as a reference electrode, taking an ion migration electrode as a working electrode, adopting a three-electrode system of the working electrode, the reference electrode and a counter electrode, under constant potential control, driving the ion migration electrode cavity to indicate the migration or the migration of ions across the electrode film by utilizing the potential change of the reference electrode polymer film ion selective electrode caused by the concentration change of the ions to be detected, thereby converting the concentration information of the ions to be detected in the solution to be detected into an analysis signal which is more sensitive than a potential signal, and realizing high-precision quantitative detection of a target in the detection solution;
the detection target is potassium ion, sodium ion, calcium ion, magnesium ion, hydrogen ion, heavy metal ion, chloride ion, nitrate ion, carbonate ion, sulfate ion and phosphate ion;
the polymer membrane ion selective electrode is an all-solid polymer membrane ion selective electrode without internal liquid filling or a liquid contact type ion selective electrode containing internal liquid filling; the polymer film ion selective electrode is prepared by coating a polymer film on the surface of a substrate or sticking the polymer film on the bottom of an electrode cavity;
the conductive substrate in the all-solid-state polymer film ion selective electrode is a disc electrode, an ITO conductive glass electrode, a screen printing electrode or a paper chip electrode; the polymer film is prepared by mixing an ion selective carrier of ions to be detected with a lipophilic ion exchanger according to a mass ratio of 1-2:1, and then according to a mass ratio of 1:2, adding a film matrix material and a plasticizer to obtain the composite material;
the ion transfer electrode is a liquid contact ion selective electrode containing an internal liquid filling; the bottom of the ion migration electrode cavity is coated with an electrode sensitive film, and the electrode sensitive film is a liquid sensitive film or a solid sensitive film;
the internal liquid of the ion transfer electrode is aqueous solution containing indication ions, wherein the indication ions are charged ions or proteins and have the same electrical property with the ions to be detected;
the liquid sensitive film is prepared by uniformly mixing a lipophilic ion exchanger and a plasticizer according to the mass ratio of 1:1-9;
the solid sensitive film is composed of 1-50% of lipophilic ion exchanger by mass, and the mass ratio of film base material to plasticizer is 1:2, mixing to obtain the product;
the detection method adopts a sample cell and a detection cell for separation, wherein a polymer membrane ion selective electrode contacted with a sample solution is arranged in the sample cell and is used for sensing the activity change of ions to be detected in the sample; the ion migration electrode and the counter electrode are arranged in the detection cell and are used for converting potential signals of the polymer membrane ion selective electrode into current signals, and the two cells are connected through a salt bridge.
2. The method for high-precision electrochemical detection of a target based on an ion-transfer amplification effect of a polymer-sensitive membrane of claim 1, wherein: the counter electrode can be a platinum wire, a platinum sheet, a platinum disk electrode or a carbon-based electrode.
3. The method for high-precision electrochemical detection of a target based on an ion-transfer amplification effect of a polymer-sensitive membrane of claim 1, wherein: the lipophilic ion exchanger is sodium tetrakis (3, 5-bis (trichloromethyl) phenyl) borate, potassium tetrakis (3, 5-bis (trichloromethyl) phenyl) borate or tri (dodecyl) methyl ammonium chloride;
the film matrix material is polyvinyl chloride, polyurethane, silicon rubber, acetate fiber, polyacrylamide or polymethyl methacrylate-dimethylaminoethyl methacrylate; the plasticizer is o-nitrophenyl octyl ether, dioctyl phthalate, dibutyl phthalate, diisobutyl phthalate, dioctyl adipate or dioctyl sebacate.
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