Electrochemical calibration-free pH sensing method based on dynamic current technology

Abstract

The invention discloses an electrochemical calibration-free pH sensing method based on a dynamic current technology. The pH sensitive probe and the pH non-sensitive probe are used for detecting the pH of the environment to be detected, when the pH sensitive probe performs quantitative pH detection, current and potential signals generated by the electrode can correspondingly change along with the change of the pH to be detected and environmental interference factors, and the potential signal only responds to the environmental interference factors. After current and potential signal values of the sensitive electrode are processed by adopting a certain method, the problem of output result drifting of the electrode caused by multiple environmental interference factors can be effectively shielded, batch calibration of the sensor can be completed after the pH-indication value relation of the sensor is determined at a time, and the pH value of a solution to be measured is measured according to a regression curve. Finally, the purpose of calibration-free pH sensing is achieved, and the resolution ratio, the reproducibility, the accuracy and the stability of dynamic current method pH quantitative analysis can be greatly improved.

Description

Technical Field

[0001] The content of the present invention belongs to the fields of electrochemical detection and analysis, and chemical sensor technology, and relates to a pH sensing method for electrochemical calibration-free based on dynamic current technology. Background Art

[0002] pH is a basic parameter in many fields such as production and life, precision manufacturing, scientific research, surveying and exploration, chemical engineering, and biological engineering, and has important and standardized application values. Precise, stable, and rapid quantification of pH is the core task in pH detection. At present, there are already mature pH sensor products, but it is difficult to meet the requirements of many high-precision in-situ monitoring scenarios, such as ocean monitoring, wearable devices, etc., because they cannot achieve calibration-free analysis. This is because the principles adopted by current mainstream technologies basically rely on the galvanic cell system composed of a sensitive membrane and a reference electrode to achieve pH quantification. Currently, there is no technology to dynamically track and compensate the half-cell electromotive force in real time, so it is difficult to avoid repeated calibration and impossible to achieve automation and long-term in-situ monitoring.

[0003] Currently, the electrochemical methods for pH quantitative analysis are generally divided into two categories: potentiometric method and dynamic current method. The main problems of the potentiometric method are almost all reflected in the glass bulb pH meter. Due to the inevitable error caused by the continuous drift of the electromotive force of the two electrodes over time, it is particularly prominent that it is difficult to achieve long-term in-situ pH precise monitoring. The dynamic current method only realizes pH quantification through potential information, and still faces problems such as insufficient accuracy, low resolution, and poor reproducibility. Therefore, it is actually difficult to achieve the calibration-free effect. On the one hand, the potential indication scheme has poor accuracy in the dynamic current method - the background noise of the probe potential measured by the dynamic current method is large; on the other hand, the probe potential indicated by the dynamic current method also depends on the effective concentration / activity of the probe at the electrode interface. To obtain an accurate probe potential, it is necessary to ensure that the effective concentration / activity of the probe remains unchanged for a long time, which is difficult to achieve in actual scenarios. Summary of the Invention

[0004] The present invention mainly aims at the above problems, fully considers the current drift problem in the analysis process of the dynamic current method, and proposes to process a certain algorithm to dynamically sensor the dynamic drift degree of the probe current signal during long-term continuous operation. And by simultaneously considering the changes in the probe potential and current to achieve more accurate pH indication, so as to truly achieve the calibration-free effect and improve the long-term analysis accuracy and stability of the sensor. At the same time, this solution fully considers the diversity of probe materials and the selection flexibility according to different scenario needs, simplifies the calculation method, and corrects the inconsistent calculation results caused by different probe materials and sensor preparation processes by introducing an electrode constant, with methodological universality.

[0005] To overcome the problem that traditional electrochemical pH sensing technology relies on repeated calibration and cannot achieve long-term in-situ full-automatic monitoring, the present invention uses a pH-sensitive (responsive) probe and a pH-insensitive (responsive) probe to detect the pH of the environment to be measured. During the pH quantitative detection process of the pH-sensitive probe, both the current and potential signals generated by the electrode will change accordingly with the changes in the pH to be measured and environmental interference factors, while the latter only responds to environmental interference factors.

[0006] The purpose of the present invention is to provide a pH sensing method based on dynamic current technology for electrochemical calibration-free. After processing the current and potential signal values of the sensitive electrode by a certain method, the present invention can effectively shield the problem of output result drift of the electrode caused by multiple environmental interference factors, that is, it can realize real-time dynamic correction of the pH measurement result, thereby achieving the purpose of calibration-free pH sensing. The calibration-free high-precision sensing of the pH of a complex aqueous solution environment can be realized by the method of the present invention, which is particularly suitable for various application scenarios that require long-term in-situ full-automatic pH quantification.

[0007] The following are specific implementation schemes:

[0008] A pH sensing method based on dynamic current technology for electrochemical calibration-free, comprising:

[0009] Using an electrode system containing a pH-sensitive probe and a pH-insensitive probe to detect the pH of a pH standard buffer solution;

[0010] Obtaining a pH indication parameter a.u. by voltammetry and defining it as where E f is the peak potential, HWHM is the half-peak half-width potential, ΔI 1 and ΔI 2 are the peak current intensities corresponding to the pH-sensitive probe and the pH-insensitive probe respectively, and a is the electrode constant;

[0011] Generating a regression curve according to the relationship between the a.u. value and the pH value of the standard buffer solution;

[0012] Using the same electrode system containing a pH-sensitive probe and a pH-insensitive probe to detect the solution to be measured, and measuring the pH value according to the regression curve;

[0013] Both the current and potential signals generated by the pH-sensitive probe will respond to the change of the pH to be measured;

[0014] The current and potential signals generated by the pH-insensitive probe do not respond to the change of pH.

[0015] Furthermore, both the current and potential signals generated by the pH-sensitive probe will respond to changes in the pH to be measured and environmental interference factors; the current and potential signals generated by the pH-insensitive probe do not change with pH and only respond to changes in environmental interference factors.

[0016] Furthermore, the interference factors mainly include ion species, ion concentration, solution viscosity, strong acids and bases, extreme temperatures, fluorides, sulfides, attachments, biological contaminants, etc. These are all environmental factors that seriously interfere with the measurement accuracy of traditional methods. This solution has good anti-interference performance against these known interference factors.

[0017] Furthermore, the pH-sensitive probe and the pH-insensitive probe can be integrated on the same substrate electrode or used separately; when on the same substrate electrode, the modification order of the two probes depends on the properties of the probe materials used and can be flexibly adjusted or optimized according to specific circumstances.

[0018] Furthermore, the pH-sensitive probe is prepared by modifying a functional material on the substrate electrode or in-situ introducing a functional material.

[0019] Furthermore, the substrate is one of pure metals, alloys, semiconductor materials, conductive glasses, special ceramics, special diamonds, special polymers, nanomaterials or a composite material composed of one or more of them; further, the pure metal is one of graphite, iridium, copper, silver, etc., the carbon material is at least one of graphite, porous carbon materials, graphene, carbon, and the special polymer is at least one of polyaniline, polythiophene, polypyrrole.

[0020] Furthermore, the functional material of the pH-sensitive probe includes but is not limited to at least one of metal oxides, metal chelates and their derivatives, benzene substances and their derivatives, heterocyclic aromatic hydrocarbons and their derivatives, electrochemically active biomolecules and their derivatives. Further, the functional material of the pH-sensitive probe includes but is not limited to at least one of iridium oxide, tin dioxide, tungsten oxide, antimony oxide, potassium ferricyanide, sodium ferricyanide, catechol, catecholamine, aminophenol, polydopamine, Nile blue A, and diprophylline.

[0021] The pH-insensitive probe is prepared by modifying a functional material on the substrate electrode or in-situ introducing a functional material.

[0022] Furthermore, the substrate electrode is one of pure metals, alloys, carbon materials, special diamonds, conductive glasses, special ceramics, semiconductor materials, special polymers, nanomaterials, etc. or a composite material composed of one or more of them.

[0023] Furthermore, the functional materials of the pH-insensitive probe include, but are not limited to, at least one of pure metals, alloys, carbon materials, metal chelates and their derivatives, benzene substances and their derivatives, heterocyclic aromatic hydrocarbons and their derivatives, and electrochemically active biomolecules and their derivatives. Further still, the functional materials of the pH-insensitive probe include, but are not limited to, at least one of silver, gold, gold amalgam, tin-lead alloy, boron-doped diamond, carbon black, glassy carbon, ruthenium bipyridine, iron phenanthroline, (poly)benzenethiol, and poly(4-vinylpyridine), etc.

[0024] Furthermore, the modification method of the functional material on the substrate electrode is at least one of chemical vapor deposition, vacuum sputtering, evaporation plating, electroplating, electrochemical deposition, chemical in-situ synthesis, electrochemical in-situ synthesis, and film formation.

[0025] Furthermore, the electrode system adopted by the pH sensing method is one of a two-electrode system, a three-electrode system, and a four-electrode system.

[0026] Furthermore, the electrode material adopted by the working electrode, the working sensing electrode, or the auxiliary electrode in the electrode system is at least one of a metal electrode, an alloy electrode, a carbon material electrode, a special diamond electrode, a conductive glass electrode, a special ceramic electrode, a semiconductor electrode, a polymer electrode, a nanomaterial electrode, etc.

[0027] Furthermore, the electrode form of each electrode in the electrode system includes, but is not limited to, at least one of a column electrode, a screen-printed electrode, an interdigitated electrode, a filament electrode, a spherical electrode, and a microelectrode.

[0028] Furthermore, the voltammetry method includes, but is not limited to, at least one of linear voltammetry, cyclic voltammetry, pulse voltammetry, differential pulse voltammetry, and square wave pulse voltammetry.

[0029] Furthermore, for linear voltammetry and cyclic voltammetry, the scanning potential window is -2.5 to +2.5 V; the scanning rate is 0.01 mV / s - 10 V / s; for pulse voltammetry, the potential increment is 0.01 - 1000 mV / s, the potential amplitude is 1 - 500 mV, and the frequency is 1 - 100000 Hz.

[0030] Furthermore, after the data is measured by voltammetry, primary processing is performed on the data, and the processing methods include, but are not limited to, linear filtering and linear parameter extraction; further still, the linear filtering includes at least one of differential filtering, high-pass filtering, and low-pass filtering; the linear parameter extraction includes at least one of derivative function analysis and judgment, non-linear fitting analysis and judgment, machine learning fitting analysis and judgment, and interpolation method analysis and judgment, etc.

[0031] Compared with the prior art, the present invention has the following technical advantages:

[0032] (1) The present invention provides a brand-new electrochemical testing method, which enables calibration-free pH quantitative analysis in electrochemistry, and has high sensitivity, high resolution, high stability, long lifespan, short response time, and convenient operation, being able to fully meet the requirements of long-term in-situ dynamic monitoring in complex environments.

[0033] (2) Compared with the conventional dynamic current method for pH quantitative analysis technology, the present invention not only utilizes the correlation between pH and the indicating potential of the electrochemical probe, but also fully considers the dynamic changes of the current signal. Through the current-potential dual-mode strategy, the pH converted from the electrochemical parameters of the dynamic current method is corrected in real time and synchronously, thereby being able to greatly improve the resolution, reproducibility, accuracy, and stability of the pH quantitative analysis of the dynamic current method. After establishing the pH-indicating quantity relationship of the sensor once, batch calibration of the sensor can be completed, and no secondary calibration or calibration is required after leaving the factory. (3) The present invention can be adapted to a variety of optimization algorithms, allowing for targeted optimization and iteration of various performance parameters such as the sensitivity, resolution, anti-interference ability, and response time of the sensor through algorithm design, and being applicable to the in-situ dynamic pH monitoring requirements of various scenarios. It is easy to realize the intelligent upgrade of the instrument at the sensor level.

[0034] (4) The pH sensors of the present invention are all all-solid-state pH electrode type sensors, which do not rely on liquid reference electrodes and do not require the use of any liquid components. On the premise of significantly enhancing the stability and service life of the sensor, it allows for two-dimensional design, miniaturization design, and flexible design of the sensor, etc., having obvious advantages for a variety of high-value-added pH analysis scenarios. Description of the Drawings

[0035] Figure 1 Differential pulse voltammogram (a) of the poly(p-aminophenol)-modified silver-plated graphite pH electrode in Britton-Robinson buffer solution with pH 2 - 12 in Example 1 and the a.u.-pH regression curve (b) plotted after converting the results to a.u. values.

[0036] Figure 2 For IrO x -Ru(bpy) 3 Square wave pulse voltammogram (a) of the modified carbon screen-printed pH electrode in Britton-Robinson buffer solution with pH 2 - 12 in Example 2 and the a.u.-pH regression curve (b) plotted after converting the results to a.u. values.

[0037] Figure 3 pH real-time online monitoring results of the poly(p-aminophenol)-modified graphite electrode, glass bulb electrode, and ISFET sensor at the same ocean test point for 100 consecutive days in Comparative Example 1.

[0038] Figure 4It is a control for the in-situ continuous pH monitoring of the 24-hour of the orifice plate type pH printing electrode array of Comparative Example 2 and the standard BCECF fluorescence method bioreactor. Detailed implementation mode

[0039] Example 1

[0040] (1) Silver electrochemical deposition on the graphite electrode

[0041] Take a graphite rod with φ = 3.0 mm and a length of 60 mm, seal its side with epoxy resin glue and polish its end face with 600-mesh sandpaper wet grinding to make a graphite electrode. Prepare an aqueous NaOH solution with a mass concentration of 6%, a AgNO 3 solution and a 1% aqueous furfural solution. Heat the aqueous NaOH solution to 80 °C and soak the graphite electrode and the inner wall of the reaction cell for 20 min. Add 30 mL of AgNO 3 solution to the reaction cell, and add 5 mL of 10% NH 3 ·H 2 O aqueous solution under shaking conditions. Add 4 mL of furfural solution to the reaction cell, and form a three-electrode system with the cleaned graphite electrode, a Pt electrode and an Ag / AgCl electrode, and make the whole system react in a water bath at 80 °C for 12 min. After the reaction, the electrode is left standing in the reaction solution for 15 min, and then taken out, rinsed with pure water and dried to make a chemically silver-plated graphite electrode.

[0042] (2) Electrochemical polymerization of p-aminophenol on the electrode

[0043] Place the chemically silver-plated graphite electrode obtained in step (1) in a 10 mM p-aminophenol solution, and use the potentiostatic deposition method to continuously treat it in a 0.1 M KCl solution containing 10 mM p-aminophenol at a constant deposition potential of 1200 mV (vs Ag / AgCl) for 160 s, and then take it out, rinse with pure water and dry to obtain a p-aminophenol-modified graphite electrode. After measurement, it is determined that the electrode constant a of this electrode is 0.081.

[0044] (3) Response test

[0045] The poly(p-aminophenol)-modified graphite electrode prepared above, a Pt electrode, and an Ag / AgCl electrode were used to form a three-electrode system. Two sets of scientific instrument-grade pH meters certified by CMA were used. After being calibrated strictly according to the instrument instructions, they were used to prepare a Britton-Robinson standard buffer solution with a concentration of 40 mM (the two sets of equipment were cross-calibrated to ensure the accuracy of the standard method). The pH of the buffer solution was adjusted to 2 - 12 with 0.5 M standard hydrochloric acid and potassium hydroxide. Differential pulse voltammetry (the scanning potential was from 800 to -500 mV, the pulse potential increment was 5 mV, the pulse amplitude was 50 mV, and the pulse frequency was 20 Hz.) was used to test the variation of current and potential with pH of the polymeric voltammetric pH electrode in the buffer solution samples, and its pH response curve was recorded. The differential pulse voltammogram in the Britton-Robinson standard buffer solution with pH 2 - 12 is as shown in Figure 1 (a). The single-chip microcomputer software automatically calculated E f , HWHM, ΔI 1 , ΔI 2 , a, and the value of a.u. according to the curve result data, recorded the relationship between the a.u. value and the pH value of the standard buffer solution to generate a regression curve, as shown in Figure 1 (b). The definite quantitative relationship of a.u.-pH of this curve was used for pH detection, that is, the three-electrode system was contacted with the solution to be measured to obtain the a.u. value, and the pH was measured according to the regression curve. On the premise that the preparation method of this sensor remains unchanged, only the regression curve parameters need to be written into the analysis circuit module of the sensor for mass production. After production, the sensor no longer needs to re-enter or update the curve parameters and can be directly used for calibration-free analysis of actual samples. The measurement results of the polymeric voltammetric pH electrode prepared according to the method of the present invention in several common samples are shown in Table 1, and the response time is 33 s. Compared with the glass pH sensor, the response time is fast and calibration is not required.

[0046] Table 1 Parameters measured by the poly(p-aminophenol)-modified silver-plated graphite pH electrode in each buffer solution

[0047]

[0048] Table 2 Measurement results of the poly(p-aminophenol)-modified silver-plated graphite pH electrode in different actual samples

[0049]

[0050] Example 2

[0051] (1) Functional modification of the surface of the iridium screen-printed electrode

[0052] Prepare a screen-printed electrode with Ir as the working electrode, C as the counter electrode, and Ag as the pseudo-reference electrode, where the diameter of the working electrode φ = 3.0 mm. Place the working surface of the electrode in a 0.1 M KNO 3 solution, apply a working voltage of 1.8 V to the Ir working electrode by potentiostatic method, take it out and wash it after continuous treatment for 120 s.

[0053] Prepare an aqueous solution containing 10 mM TCEP and 2.5 mM 4,4'-bis(5-hexylthio-2-thienyl)-2,2'-bipyridine with 0.1 M PBS buffer solution at pH 7.0. Immerse the clean working surface part of the electrode fully into this solution, take it out and wash it after constant temperature treatment at 50 °C for 60 min. Prepare a 10 mM RuCl 3 ·6H 2 O solution with 0.1 M HCl solution, immerse the working surface of the electrode into the solution and keep it at room temperature for 15 min, then take it out and wash it. Immerse the working surface part of the electrode into a 6 mM bipyridine solution prepared with 0.1 M PBS buffer solution at pH 7.0, take it out and wash it after treatment at room temperature for 120 min to obtain a functionalized iridium screen-printed electrode, where IrOx is a pH-sensitive probe and tris(2,2′-bipyridine)ruthenium(II) hexahydrate, i.e., the ruthenium-based complex Ru(bpy) 3 is a non-pH-sensitive probe. After measurement, it is determined that the electrode constant a of this electrode is 0.176.

[0054] (2) Response test

[0055] Use the above-prepared functionalized iridium screen-printed electrode to form a three-electrode system with a Pt electrode and an Ag electrode. Adopt square wave pulse voltammetry to test the changes of current and potential with pH in the Britton-Robinson standard buffer solution samples with pH 2 - 12 configured in the same method as described in Example 1 of this article, record its pH-response curve. The square wave voltammogram in the Britton-Robinson buffer solution with pH 2 - 12 is as shown in Figure 2 (a). The single-chip microcomputer software automatically calculates E f , HWHM, ΔI 1 , ΔI 2 , a and a.u. values according to the curve result data, record the relationship between the a.u. value and the pH value of the standard buffer solution to generate a regression curve, as shown in Figure 2 (b). The system generates a regression curve for pH detection. Test the pH of several common samples with the functionalized iridium screen-printed electrode prepared according to the method of the present invention. The results are shown in Table 2, and the response time is 15 s. Compared with the glass pH sensor, the response time is fast and calibration is not required.

[0056] Table 3 Parameters measured by the functionalized iridium screen-printed electrode in each buffer solution

[0057]

[0058] Table 4 IrO x -Ru(bpy) 3 Determination results of the modified carbon screen-printed pH electrode in different actual samples

[0059]

[0060] Comparative Example 1

[0061] Using a three-electrode system composed of the poly(p-aminophenol)-modified graphite electrode prepared in Example 1, an imported glass bulb electrode, and an imported ISFET sensor, three pH sensors simultaneously started in-situ ocean pH monitoring at the same test site in a certain sea area of Shenzhen. The test average depth was 5 m, the test seawater temperature was 15.3 - 32.5 °C, the test average salinity was 31.2‰, and continuous recording was carried out for 100 days.

[0062] The test results are as Figure 3 shown. During the 100-day continuous in-situ monitoring process: The readings of the ISFET-type pH sensor remained at about 8.18 for several days without change, and then began to gradually change after 20 days. By the 75th day of continuous monitoring, the result had drifted to the level of ~8.52, and the maximum drift amplitude formed within 100 days was 0.74 pH units; The readings of the standard glass bulb pH meter were basically stable at ~8.23 within 20 days, and then obvious signal drift occurred, and the maximum drift amplitude formed within 100 days was 0.60 pH units; While the poly(p-aminophenol)-modified graphite electrode did not show significant signal drift within 100 days, and the maximum drift amplitude was only 0.02 pH units. It shows that the sensor described in this scheme shows extremely strong stability in the long-term in-situ monitoring of ocean pH, and shows significant advantages in this performance compared with the standard method and the market-leading technology method. After the test, it was found by observation that each sensor probe was tightly covered by marine microbial films and marine organisms, and the formed biofouling was serious, which may be the reason for the obvious signal drift in the long-term test of the two comparison methods. In contrast, although the sensor described in this scheme was also fouled at the same level, no obvious signal drift occurred, indicating that the method described in this scheme can well overcome the interference caused by the fouling of the sensor in a complex environment.

[0063] Comparative Example 2

[0064] (1) Preparation of 96-well plate-type pH printed electrode array

[0065] Print a screen-printed electrode with Ir as the working electrode, C as the counter electrode, and Ag as the pseudo-reference electrode. The three electrodes are distributed in a concentric circle layout and printed into an electrode array of 96 groups according to the arrangement mode of a commercially available 96-well plate. The wire part is distributed on four sides. Among them, the electrode part has a diameter of φ = 4.0 mm. Immerse the electrode in 0.1 M KNO 3 solution and apply a working voltage of 1.8 V to the Ir working electrode by potentiostatic method. After continuous treatment for 120 s, take it out and wash it. Prepare an aqueous solution containing 10 mM TCEP and 2.5 mM 4,4'-bis(5-hexylthio-2-thienyl)-2,2'-bipyridine with 0.1 M PBS buffer solution at pH 7.0. Immerse the clean electrode working surface part fully into this solution, take it out and wash it after constant temperature treatment at 50 °C for 60 min. Prepare a 10 mM RuCl 3 ·6H 2 O solution with 0.1 M HCl solution. Immerse the electrode working surface into the solution and keep it at room temperature for 15 min, then take it out and wash it. Immerse the electrode working surface part into a 6 mM bipyridine solution prepared with 0.1 M PBS buffer solution at pH 7.0, take it out and wash it after treatment at room temperature for 120 min.

[0066] Make a double-sided transparent plate the same as a commercially available 96-well plate with a PS board. Coat UV curable glue on one side, cure it after docking with the screen-printed electrode array to form a 96-well plate with a pH electrode array.

[0067] (2) In-situ continuous pH monitoring of bioreactor

[0068] Dissolve 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) in DMSO and dilute it with 0.01 M PBS at pH 7.4 to make a solution with a content of 5 μM. Select the HEK293 cell line, take out the frozen HEK293 cells and quickly put them into a 37 °C water bath to thaw. Use DMEM + 10% fetal bovine serum as the culture medium and preheat it to 37 °C for standby. Add the thawed cell suspension into a centrifuge tube containing the preheated culture medium, gently pipette and mix well. Centrifuge to remove the supernatant, resuspend the cells with fresh culture medium, and inoculate them into a culture dish. Place the culture dish in an incubator at 37 °C and 5% CO 2 and culture until the cells reach the logarithmic growth phase. When the cell confluence reaches 80%-90%, perform cell passage. Digest the cells with trypsin, collect the cell suspension, and centrifuge to remove trypsin. Resuspend the cells with fresh culture medium and inoculate them into a new culture dish at a ratio of 1:4 and continue to culture. Select cells in the logarithmic growth phase for plating. Adjust the cell suspension to 1×10 5cells / mL concentration, add 80 μL of cell suspension and 20 μL of BCECF solution to each well of a 96-well plate and mix well. Fill the edge wells with sterile PBS to reduce edge effects. Place the cell culture system back to 37°C and 5% CO in the 96-well plate. 2 Incubate in an incubator for 24 hours, and continuously monitor the pH level and changes of the system with the plate's own electrode or spectrometer. During this period, 5 mM 2-deoxy-D-glucose was added at 8 hours, and the culture and data collection continued.

[0069] The results are as follows Figure 4 As shown, it can be seen that after the addition of the anaerobic glycolysis promoter, the pH of the culture medium recorded by the classical fluorescence method and the electrode of the present invention both showed the same trend of decrease. Moreover, the dynamic pH level values ​​recorded in each period are highly consistent. This shows that the present method can accurately monitor the real-time pH level and changes in the biomicroreactor process, and its precision and accuracy can reach the same level as the classical method. Moreover, the present method does not require the use of an indicator and can achieve continuous, in-situ, non-destructive pH monitoring.

Claims

1. A method for electrochemical calibration-free pH sensing based on dynamic current technology, characterized in that include: The pH of the pH standard buffer solution is detected using an electrode system containing a pH sensitive probe and a pH insensitive probe; The pH indicator parameter au obtained by voltammetric analysis is defined as Where E f is the peak potential, HWHM is the half-width at half maximum potential, ΔI1 and ΔI2 are the peak current intensities corresponding to the pH sensitive probe and the pH insensitive probe, respectively, and a is the electrode constant; A regression curve was generated based on the relationship between the au value and the pH value of the standard buffer solution; The solution to be tested is detected using an electrode system containing the same pH sensitive probe and pH insensitive probe, and the pH value is measured according to the regression curve; The current and potential signals generated by the pH sensitive probe will respond to changes in the pH to be measured; The current and potential signals generated by the pH insensitive probe do not respond to changes in pH.

2. The pH sensing method according to claim 1, characterized in that: The pH sensitive probe and the pH insensitive probe are prepared by modifying a functional material on a substrate electrode or introducing a functional material in situ.

3. The pH sensing method according to claim 2, characterized in that: The base electrode is one of pure metal, alloy, carbon material, special diamond, conductive glass, special ceramic, semiconductor material, special polymer, nano material or a composite material composed of more than one of them.

4. The pH sensing method according to claim 2, characterized in that: The functional material of the pH sensitive probe is not limited to at least one of metal oxides, metal chelates and their derivatives, benzene series substances and their derivatives, heterocyclic aromatic hydrocarbons and their derivatives, and electrochemically active biomolecules and their derivatives; The functionalized material of the pH-insensitive probe includes, but is not limited to, at least one of pure metals, alloys, carbon materials, metal chelates and their derivatives, benzene-based substances and their derivatives, heterocyclic aromatic hydrocarbons and their derivatives, and electrochemically active biomolecules and their derivatives.

5. The pH sensing method according to claim 2, characterized in that: The functionalized material of the pH sensitive probe includes but is not limited to at least one of iridium oxide, tin dioxide, tungsten oxide, antimony oxide, potassium ferric hexacyanoferrate, sodium ferric hexacyanoferrate, catechol, catecholamine, aminophenol, polydopamine, Nile blue A and dihydroxypropylphylline; The functionalized material of the pH-insensitive probe includes but is not limited to at least one of silver, gold, gold amalgam, tin-lead alloy, boron-doped diamond, carbon black, glassy carbon, bipyridine ruthenium, phenanthroline iron, (poly) benzenethiol and poly (4-vinylpyridine).

6. The pH sensing method according to claim 1, characterized in that: The electrode system adopted by the pH sensing method is one of a double electrode, a triple electrode and a quadruple electrode.

7. The pH sensing method according to claim 6, characterized in that: The electrode material used for the reaction electrode, reaction sensing electrode or auxiliary electrode in the electrode system is at least one of a metal electrode, an alloy electrode, a carbon material electrode, a special diamond electrode, a conductive glass electrode, a special ceramic electrode, a semiconductor electrode, a polymer electrode and a nanomaterial electrode; The electrode form of each electrode in the electrode system includes but is not limited to at least one of a column electrode, a screen-printed electrode, an interdigitated electrode, a wire electrode, a spherical electrode, and a microelectrode.

8. The pH sensing method according to claim 1, characterized in that: The voltammetric analysis method includes, but is not limited to, at least one of linear voltammetry, cyclic voltammetry, pulse voltammetry, differential pulse voltammetry, and square wave pulse voltammetry.

9. The pH sensing method according to claim 1, characterized in that: The current and potential signals generated by the pH sensitive probe will respond to changes in the pH to be measured and environmental interference factors; The current and potential signals generated by the pH-insensitive method do not respond to changes in pH but only to changes in environmental interference factors.

10. The pH sensing method according to claim 1, characterized in that: After the data are measured by voltammetric analysis, primary processing is performed on the data, and the processing methods include but are not limited to linear filtering and linear parameter extraction.

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