Cobalt ion detection method based on ion imprinted polymer modified electrode

Abstract

The invention relates to the technical field of electrochemical analysis, and discloses a cobalt ion detection method based on an ion imprinted polymer modified electrode, and the method comprises the following steps: constructing a microfluidic system, and carrying out electrochemical polymerization by enabling a precursor solution to dynamically flow through the electrode to realize uniform growth of a modification layer and dynamic embedding of Co < 2 + >; then applying pulse potential to efficiently elute Co < 2 + >; and finally, performing electrochemical detection after re-combining to-be-detected Co < 2 + >. According to the scheme, imprinting sites are uniformly distributed, the template agent is rapidly and efficiently eluted, and the cobalt ion detection performance, reproducibility and preparation efficiency are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical analysis technology and relates to a method for detecting cobalt ions based on ion-imprinted polymer-modified electrodes. Background Technology

[0002] Cobalt ions, as a key trace element, play a significant role in biological, environmental, and industrial fields. In living organisms, they are a core component of vitamin B12, supporting normal physiological functions; in industry, they are commonly used in catalysts, battery materials, and alloy manufacturing. However, abnormal cobalt ion concentrations can have adverse effects in environmental water pollution detection, industrial wastewater, and biological sample analysis. Therefore, developing highly sensitive, selective, rapid, and accurate detection methods is of great significance for environmental monitoring, industrial control, and biomedical diagnostics. Electrochemical sensing technology has become a research hotspot for cobalt ion detection due to its simplicity, low cost, fast response, and ease of miniaturization and integration. Among them, ion-imprinted polymer-modified electrodes, with their unique molecular recognition capabilities, show great potential in improving sensor selectivity and sensitivity. For a long time, the preparation of such modified electrodes has mostly adopted a static polymerization process: target ions (templates), functional monomers, crosslinking agents, initiators, etc. are mixed on the electrode surface or in a reaction vessel, and polymerization is initiated in a static state. The functional monomers form a specific spatial conformation around the template ions, and are cured by the crosslinking agent to form a polymer network with recognition sites. After the template ions are washed away, imprinted sites matching the template ions are left in the polymer, achieving specific recognition and binding. This method initially solved the problem of poor selectivity of bare electrodes or ordinary modified electrodes in complex matrices, laying the foundation for the development of new sensors and improving detection sensitivity to a certain extent. However, with technological advancements and increasing performance requirements, the inherent defects of traditional static polymerization have become increasingly apparent. In static systems, the local concentrations of template agents, functional monomers, and crosslinking agents on the electrode surface are prone to uneven distribution. During polymerization, some template ions may be embedded deep within the polymer early on, resulting in poor recognition site structure, spatial obstruction, or even blockage by new polymer chains, thus losing their binding ability. Moreover, the recognition sites formed in a static environment are randomly distributed, with poor uniformity and accessibility, directly affecting the electrode's binding efficiency and response performance to target ions. More importantly, this uneven site distribution and deep embedding of template ions significantly increase the difficulty of subsequent elution. The diffusion path of template ions from the polymer is long and tortuous, and elution often takes several hours. Even so, some template ions remain, affecting the quantity and quality of the blotted sites and introducing background interference, thus reducing detection accuracy and sensitivity.

[0003] Fundamentally, static polymerization cannot precisely control polymer formation kinetics and microstructural evolution. The disordered growth of polymer chains and random embedding of template molecules inevitably lead to heterogeneity in the imprinted sites—significant differences in binding affinity, kinetics, and spatial accessibility at different sites. This is the root cause of poor electrode reproducibility, resulting in large fluctuations in response signals between different batches or even within the same batch, making it difficult to meet the requirements of high-precision quantitative analysis for trace detection. Simultaneously, prolonged elution reduces the efficiency of batch electrode preparation, increases costs, and hinders the widespread adoption of these modified electrodes in rapid-response, high-throughput preparation scenarios. Summary of the Invention

[0004] This invention provides a method for cobalt ion detection based on ion-imprinted polymer-modified electrodes, addressing the technical challenges of traditional static polymerization-based ion-imprinted polymer-modified electrodes, including uneven mass transfer, disordered recognition site distribution, deep embedding of template agents, excessively long elution times, and poor electrode reproducibility. By introducing a microfluidic dynamic reaction system and precise electrochemical control strategies, this invention achieves uniform and controllable growth of the ion-imprinted polymer modification layer and efficient and rapid elution of the template agent, thereby significantly improving the detection performance, reproducibility, and preparation efficiency of the modified electrode for cobalt ions.

[0005] To achieve the above-mentioned objectives, this invention provides a method for detecting cobalt ions based on an ion-imprinted polymer-modified electrode, comprising the following steps: In a first aspect, the present invention provides a method for detecting cobalt ions based on an ion-imprinted polymer-modified electrode, which mainly includes two stages: preparation of the modified electrode and electrochemical detection of cobalt ions.

[0006] In the preparation stage of the modified electrode, the preparation method of the ion-imprinted polymer modified electrode used in this invention specifically includes the following steps: Step one: Constructing the microfluidic reaction system. The microfluidic reaction system consists of a microfluidic chip, a high-precision liquid delivery module, and an electrochemical workstation. The microfluidic chip employs a multilayer composite structure, with its substrate being borosilicate glass, which possesses excellent chemical stability and optical transparency. A precisely dimensional array of microchannels is formed on the substrate surface using photolithography and wet etching processes. The typical cross-sectional dimensions of the microchannels are 200 μm wide and 100 μm high to ensure a stable laminar flow state during subsequent liquid delivery.

[0007] The microfluidic chip integrates at least one working electrode, one counter electrode, and one quasi-reference electrode. The working electrode is preferably a 100 nm thick gold thin film electrode formed at the bottom of the microchannel using a sputtering deposition process. The effective reaction area of ​​the gold thin film electrode is precisely defined by an insulating layer. The counter electrode is preferably a platinum thin film electrode formed within the microchannel using a similar process.

[0008] The quasi-reference electrode is preferably a silver / silver chloride electrode formed on the chip using a silver chloride electroplating process. The microfluidic chip is isolated from the external environment by a sealed structure and is connected to an external high-precision liquid delivery module only through preset inlet and outlet ports.

[0009] The high-precision liquid delivery module is preferably composed of multiple independently controlled micropumps, which are used to precisely control the flow rates of the reaction precursor solution and the washing solution. The electrochemical workstation is connected to the integrated electrode on the microfluidic chip via wires for applying potential, controlling current, and performing subsequent electrochemical measurements.

[0010] Step two: Prepare and deliver the precursor solution. The precursor solution includes a functional monomer solution, a template agent solution, and an electrolyte solution. The functional monomer solution is preferably a solution of o-phenylenediamine in a specific solvent, wherein the concentration of o-phenylenediamine ranges from 5 mM to 20 mM, and its purity is analytical grade.

[0011] The template agent solution is preferably a solution of cobalt(II) chloride hexahydrate in the same solvent, wherein the concentration of cobalt(II) chloride hexahydrate ranges from 0.1 mM to 1.0 mM, and its purity is analytical grade. The electrolyte solution is preferably a 0.1 M phosphate buffer solution with its pH precisely controlled at 5.0. The phosphate buffer solution is prepared from disodium hydrogen phosphate and sodium dihydrogen phosphate to provide good conductivity and pH buffering capacity.

[0012] Each micro-injection pump of the high-precision liquid delivery module loads the functional monomer solution, the template agent solution, and the electrolyte solution, respectively. Before the polymerization reaction begins, the microchannel is first pre-cleaned with the electrolyte solution to ensure the cleanliness and uniformity of the internal environment. Subsequently, the functional monomer solution, the template agent solution, and the electrolyte solution are synchronously injected into the microchannel through the high-precision liquid delivery module at a preset precise flow rate, allowing the three components to form a stable laminar mixture on the electrode surface and continuously renew it. The precise control system of the injection pumps ensures the stability of the mixing ratio of each component within the microchannel and the uniformity of local concentration.

[0013] Step 3: Perform dynamic electrochemical polymerization. While the precursor solution continuously flows over the surface of the working electrode, the electrochemical workstation applies a constant potential to the working electrode through the quasi-reference electrode. The constant potential is preferably in the range of 0.8V to 1.2V (relative to the silver / silver chloride quasi-reference electrode). The duration of the electrochemical polymerization process is preferably 10 to 30 minutes to ensure the formation of a uniformly thick and dense polymer film on the surface of the working electrode. During this dynamic electrochemical polymerization process, the functional monomer (o-phenylenediamine) undergoes oxidative polymerization under the constant potential to form a poly(o-phenylenediamine) network.

[0014] Because the precursor solution flows continuously within the microchannels, fresh functional monomers and cobalt ions, the template agent, are continuously replenished to the surface of the working electrode, while byproducts generated during the polymerization reaction are rapidly carried away. This dynamic mass transfer mechanism effectively avoids the polymerization inhomogeneity problem caused by local concentration gradients in traditional static polymerization. During polymer growth, the cobalt ions, the template agent, are dynamically embedded or adsorbed into the forming polymer network and serve as a template for molecular imprinting.

[0015] The continuous flow environment ensures the sustained accessibility of the template agent cobalt ions at the polymer growth front, thus avoiding the problem of the template agent being embedded too quickly or too deeply in the polymer matrix, leading to unreachable recognition sites. The resulting ion-imprinted polymer modification layer exhibits a highly uniform distribution of imprinted sites and excellent site accessibility. The poly(o-phenylenediamine) network is formed through its inherent cross-linking mechanism, containing multiple nitrogen atoms that can form stable coordination interactions with cobalt ions.

[0016] Step four involves pulsed electrochemical elution. After the dynamic electrochemical polymerization is completed, the microchannel is first thoroughly cleaned with a pure electrolyte solution to remove residual unpolymerized monomers and free template agent. Subsequently, the electrochemical workstation applies a pulsed potential to the modified working electrode to achieve rapid and efficient elution of the cobalt template agent. The pulsed potential is preferably in the range of -0.5V to -0.8V (relative to the silver / silver chloride quasi-reference electrode), and the pulse width is preferably 50ms to 150ms. The pulse repetition frequency is preferably 1Hz to 5Hz.

[0017] The total duration of the pulsed electrochemical elution process is preferably 5 to 15 minutes. During the pulsed electrochemical elution process, a cleaning solution is continuously introduced into the microchannel at a low flow rate to promptly remove the eluted template agent from the electrode surface. The negative pulse potential can induce transient conformational changes or local charge state changes in the poly(o-phenylenediamine) matrix, thereby weakening the coordination or electrostatic interaction between the polymer and the template agent cobalt ions.

[0018] The instantaneous and periodic nature of the pulse generates a dynamic desorption force and promotes the diffusion rate of cobalt ions within the polymer matrix, thereby overcoming the diffusion limitation problem present in traditional static elution and achieving efficient and complete removal of cobalt ions from the template agent. Compared with traditional long-term chemical immersion elution methods, the pulsed electrochemical elution method significantly shortens the elution time (from several hours to several minutes), while ensuring the integrity and activity of the imprinted sites and minimizing template agent residue.

[0019] In the electrochemical detection stage of cobalt ions, the cobalt ion detection method of the ion-imprinted polymer-modified electrode provided by this invention specifically includes the following steps: Step 1: Introduce the sample to be tested and allow for rebinding. After eluting the template agent and thoroughly cleaning the microchannel with a pure electrolyte solution, the sample solution containing the cobalt ions to be tested is injected into the microchannel at a preset flow rate through the high-precision liquid delivery module. The sample is then allowed to remain on the eluted ion-imprinted polymer-modified electrode surface for a period of time to allow the cobalt ions to be tested to selectively bind to the imprinted sites.

[0020] The rebinding duration is preferably 10 to 30 minutes to ensure that the cobalt ions to be tested have sufficient time to diffuse and bind to the imprinted sites. During the rebinding process, the flow rate of the sample solution is precisely controlled by a microfluidic system, enabling a dynamic rebinding process and further improving binding efficiency and uniformity. The imprinted sites have a high specificity for recognizing cobalt ions, effectively eliminating the influence of other interfering ions in complex sample matrices.

[0021] Step two involves electrochemical signal detection. After the recombination of the cobalt ions to be tested is completed, the microchannel is thoroughly cleaned again with a pure electrolyte solution to remove unbound cobalt ions and non-specific adsorbed substances from the sample matrix. Subsequently, the electrochemical workstation performs electrochemical measurements on the working electrode. The preferred electrochemical measurement method is differential pulse voltammetry or square wave voltammetry.

[0022] The measurement parameters of the differential pulse voltammetry or square wave voltammetry include: the potential scan range (e.g., from +0.2V to -0.5V relative to the silver / silver chloride quasi-reference electrode), pulse amplitude, pulse width, scan rate, and sampling interval. During the potential scan, the redox peak current associated with cobalt ions bound to the imprinted sites is detected. The typical reduction peak potential of the cobalt ions typically appears between -0.1V and -0.3V (relative to the silver / silver chloride quasi-reference electrode).

[0023] The magnitude of the peak current is directly related to the concentration of cobalt ions bound to the imprinted sites, thus enabling quantitative analysis of the cobalt ion concentration in the sample. The electrochemical workstation acquires, processes, and analyzes the detected current signal, and calculates the accurate concentration of cobalt ions in the sample using a pre-established calibration curve.

[0024] In this invention, the cobalt ion detection method based on ion-imprinted polymer-modified electrodes utilizes polydimethylsiloxane as the cover material in the microfluidic chip. This facilitates bonding with the glass substrate and provides good flexibility and biocompatibility. The microchannels can be designed in a serpentine or helical structure to increase the reaction path length, thereby improving reaction efficiency and material mixing uniformity within a limited chip area. The microfluidic reaction system can further integrate a temperature control module to provide precise temperature control during the dynamic electrochemical polymerization and subsequent detection processes, ensuring the stability and reproducibility of the reaction kinetics and electrochemical response.

[0025] In this invention, the preparation of the functional monomer solution and template agent solution can be carried out in an oxygen-free environment to prevent oxidative degradation of the monomer or template agent, thereby ensuring the activity of the polymerization reaction and the quality of the final modified layer. The high-precision liquid delivery module can be further configured with an online mixer to more thoroughly mix the precursor solution before it enters the microchannel, thereby improving the uniformity of the reactant concentration on the electrode surface.

[0026] In this invention, the cleaning solution used in the pulsed electrochemical elution process can be adjusted according to actual needs, for example, using a solution with a specific pH value or containing a complexing agent to further improve the elution efficiency of the template agent. However, when using a corrosive cleaning solution, it is necessary to ensure that the microfluidic chip material and integrated electrode have sufficient corrosion resistance. In the electrochemical signal detection process, in addition to differential pulse voltammetry or square wave voltammetry, cyclic voltammetry can also be used for preliminary electrochemical characterization to confirm the effectiveness of imprint site formation and cobalt ion recombination.

[0027] Compared with the prior art, the beneficial effects of the present invention are: First, this invention achieves a highly uniform distribution and highly accessible recognition sites in the ion-imprinted polymer modification layer. Through a microfluidic dynamic reaction system, this invention establishes a continuously updated, uniformly concentrated reaction microenvironment on the electrode surface. The functional monomer and template cobalt ions can be continuously supplied to the growing polymer front in a controlled manner, effectively avoiding the localized polymerization unevenness caused by reactant concentration gradients in traditional static polymerization. This dynamic binding mechanism ensures that the template cobalt ions are effectively embedded in the shallow surface layer of the polymer network during polymer growth, thereby forming a large number of structurally uniform and spatially accessible imprinted sites. This precise microstructure control significantly improves the binding efficiency and response performance of the modified electrode for the target cobalt ions.

[0028] Secondly, this invention achieves rapid, efficient, and complete elution of the template agent. The pulsed electrochemical elution method introduced in this invention dynamically induces conformational changes in the polymer matrix and enhances ion transport at the molecular level by applying a negative pulse potential with specific parameters, thereby completing the desorption and removal of cobalt ions from the template agent in an extremely short time. Compared with traditional static chemical elution methods that take several hours, this invention significantly improves elution efficiency, greatly shortens the electrode preparation cycle, and effectively avoids template agent residue, thus eliminating its potential influence as background interference and ensuring the purity and high activity of the imprinted sites.

[0029] Third, the reproducibility and consistency of the modified electrode are significantly improved. Due to the precise control of the reaction environment during the dynamic polymerization process and the resulting uniformity of the imprinted sites, the performance differences of the ion-imprinted polymer-modified electrode prepared in this invention are significantly reduced both batch-to-batch and within-batch. This is directly reflected in the improved reproducibility of the electrochemical detection signal, thereby meeting the stringent requirements for high-precision quantitative detection in the field of microanalysis.

[0030] Fourth, it improves the sensitivity and selectivity of cobalt ion detection. The high accessibility and uniformity of the imprinted sites allow more target cobalt ions to effectively bind to the imprinted sites, thereby enhancing the electrode's signal response and improving detection sensitivity. Simultaneously, the inherent molecular recognition properties of the ion-imprinted polymer, combined with the optimized imprinted site quality of this invention, ensure specific recognition of cobalt ions in complex sample matrices, effectively eliminating interference from other similar ions and guaranteeing detection accuracy and selectivity.

[0031] Fifth, it possesses the potential for high-throughput fabrication and integrated applications. The combination of microfluidic chip technology and automated liquid delivery modules enables the method of this invention to achieve mass and automated fabrication of modified electrodes, significantly improving production efficiency. Simultaneously, the miniaturization and integration of the entire system facilitates its development into portable or online monitoring devices, broadening the practical application scope of ion-imprinted polymer-modified electrodes in environmental monitoring, industrial process control, and biomedical diagnostics. Detailed Implementation

[0032] This invention provides a method for cobalt ion detection based on ion-imprinted polymer-modified electrodes. This method, by tightly integrating a microfluidic dynamic reaction system with a precise electrochemical control strategy, aims to solve the inherent technical challenges of traditional static polymerization-prepared ion-imprinted polymer-modified electrodes, such as uneven mass transfer, disordered distribution of recognition sites, deep embedding of template agents, excessively long elution times, and poor electrode reproducibility. Ultimately, it achieves rapid, sensitive, selective, and highly reproducible detection of cobalt ions.

[0033] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0034] Example 1: Construction of a microfluidic reaction system: The microfluidic chip substrate is borosilicate glass, with microchannels having a cross-sectional dimension of 200 μm width and 100 μm height, sealed by plasma bonding using a polydimethylsiloxane cap. The working electrode is a 100 nm thick gold thin film electrode with an effective reaction area of ​​0.5 μm². 2 The counter electrode is a 100nm thick platinum thin film electrode; the quasi-reference electrode is a silver / silver chloride electrode. The high-precision liquid delivery module consists of multiple independently controlled micro-injection pumps with flow rate stability of ±0.5%. The electrochemical workstation is connected to the integrated electrode.

[0035] Precursor solution preparation and delivery: The functional monomer solution was a 5 mM o-phenylenediamine aqueous solution, the template agent solution was a 0.1 mM cobalt chloride hexahydrate aqueous solution, and the electrolyte solution was a 0.1 M pH 5.0 phosphate buffer solution. All three solutions were prepared in an oxygen-free environment filled with high-purity nitrogen. The microchannel was first pre-cleaned with the electrolyte solution, and then the three solutions were simultaneously injected into the microchannel at a total flow rate of 5 μL / min.

[0036] Dynamic electrochemical polymerization: An electrochemical workstation applies a constant potential of 0.8V (relative to the silver / silver chloride quasi-reference electrode) to the working electrode for 10 minutes to form a 100nm thick polymer film.

[0037] Pulsed electrochemical elution: After the microchannel was cleaned with a pure electrolyte solution, a pulse potential of -0.5V (relative to the silver / silver chloride quasi-reference electrode) was applied, with a pulse width of 50ms, a repetition frequency of 1Hz, and a total duration of 5min. The cleaning solution was then introduced into the microchannel at a flow rate of 1μL / min.

[0038] Cobalt ion detection: A sample solution containing the cobalt ions to be tested was injected into the microchannel at a rate of 2 μL / min and allowed to recombine on the modified electrode surface for 10 minutes. After cleaning, differential pulse voltammetry was used for detection. The potential scan range was 0.2 V to -0.5 V (relative to a silver / silver chloride quasi-reference electrode), with a pulse amplitude of 50 mV, a pulse width of 50 ms, a scan rate of 20 mV / s, and a sampling interval of 5 ms. The cobalt ion concentration was calculated based on the peak current and calibration curve.

[0039] Example 2: Construction of a microfluidic reaction system: Same as Example 1.

[0040] Precursor solution preparation and delivery: The functional monomer solution was a 10 mM o-phenylenediamine aqueous solution, the template agent solution was a 0.5 mM cobalt chloride hexahydrate aqueous solution, and the electrolyte solution was a 0.1 M pH 5.0 phosphate buffer solution. The preparation environment was the same as in Example 1. After microchannel pre-cleaning, the three solutions were injected simultaneously at a total flow rate of 7 μL / min.

[0041] Dynamic electrochemical polymerization: A constant potential of 1.0V (relative to the silver / silver chloride quasi-reference electrode) was applied for 20 minutes to form a 120nm thick polymer film.

[0042] Pulsed electrochemical elution: After cleaning, a pulse potential of -0.6V (relative to the silver / silver chloride quasi-reference electrode) is applied with a pulse width of 100ms, a repetition frequency of 3Hz, and a total duration of 10 minutes. The cleaning solution is introduced into the microchannel at a flow rate of 2μL / min.

[0043] Cobalt ion detection: The sample solution was injected at a flow rate of 3 μL / min, and the rebinding time was 15 min. The detection method and parameters were the same as in Example 1.

[0044] Example 3: Construction of a microfluidic reaction system: Same as Example 1.

[0045] Precursor solution preparation and delivery: The functional monomer solution was a 15 mM o-phenylenediamine aqueous solution, the template agent solution was a 0.8 mM cobalt chloride hexahydrate aqueous solution, and the electrolyte solution was a 0.1 M pH 5.0 phosphate buffer solution. The preparation environment was the same as in Example 1. After microchannel pre-cleaning, the three solutions were injected simultaneously at a total flow rate of 8 μL / min.

[0046] Dynamic electrochemical polymerization: A constant potential of 1.1V (relative to the silver / silver chloride quasi-reference electrode) was applied for 25 min to form a 140 nm thick polymer film.

[0047] Pulsed electrochemical elution: After cleaning, a pulse potential of -0.7V (relative to the silver / silver chloride quasi-reference electrode) was applied with a pulse width of 120ms, a repetition frequency of 4Hz, and a total duration of 12 minutes. The cleaning solution was introduced into the microchannel at a flow rate of 2.5μL / min.

[0048] Cobalt ion detection: The sample solution was injected at a flow rate of 4 μL / min, and the rebinding time was 20 minutes. The detection method and parameters were the same as in Example 1.

[0049] Example 4: Construction of a microfluidic reaction system: The microchannels of the microfluidic chip are designed with a serpentine structure, and the rest is the same as in Example 1.

[0050] Precursor solution preparation and delivery: The functional monomer solution was an 18 mM o-phenylenediamine aqueous solution, the template agent solution was a 0.9 mM cobalt chloride hexahydrate aqueous solution, and the electrolyte solution was a 0.1 M pH 5.0 phosphate buffer solution. The preparation environment was the same as in Example 1. After microchannel pre-cleaning, the three solutions were injected simultaneously at a total flow rate of 9 μL / min.

[0051] Dynamic electrochemical polymerization: A constant potential of 1.1V (relative to the silver / silver chloride quasi-reference electrode) was applied for 28 minutes to form a 145 nm thick polymer film.

[0052] Pulsed electrochemical elution: After cleaning, a pulse potential of -0.7V (relative to the silver / silver chloride quasi-reference electrode) was applied with a pulse width of 140ms, a repetition frequency of 4.5Hz, and a total duration of 14 minutes. The cleaning solution was introduced into the microchannel at a flow rate of 2.8μL / min.

[0053] Cobalt ion detection: The sample solution was injected at a flow rate of 4.5 μL / min, and the rebinding time was 25 min. The detection method and parameters were the same as in Example 1.

[0054] Example 5: Construction of a microfluidic reaction system: The microfluidic reaction system integrates a micro temperature controller based on the Peltier effect, and the temperature is controlled at 25℃±0.1℃. The rest is the same as in Example 1.

[0055] Precursor solution preparation and delivery: The functional monomer solution was a 20 mM o-phenylenediamine aqueous solution, the template agent solution was a 1.0 mM cobalt chloride hexahydrate aqueous solution, and the electrolyte solution was a 0.1 M pH 5.0 phosphate buffer solution. The preparation environment was the same as in Example 1. After microchannel pre-cleaning, the three solutions were injected simultaneously at a total flow rate of 10 μL / min.

[0056] Dynamic electrochemical polymerization: A constant potential of 1.2V (relative to the silver / silver chloride quasi-reference electrode) was applied for 30 minutes to form a 150nm thick polymer film.

[0057] Pulsed electrochemical elution: After cleaning, a pulse potential of -0.8V (relative to the silver / silver chloride quasi-reference electrode) is applied with a pulse width of 150ms, a repetition frequency of 5Hz, and a total duration of 15min. The cleaning solution is introduced into the microchannel at a flow rate of 3μL / min.

[0058] Cobalt ion detection: The sample solution was injected at a flow rate of 5 μL / min, and the rebinding time was 30 minutes. The detection method and parameters were the same as in Example 1.

[0059] Comparative Example 1 (Traditional Static Polymerization vs. Static Chemical Elution): Electrode Preparation: Using traditional static polymerization, the working electrode, counter electrode, and quasi-reference electrode were placed in a reaction vessel. A mixture of 5 mM o-phenylenediamine, 0.1 mM cobalt chloride hexahydrate, and 0.1 M pH 5.0 phosphate buffer solution was added. Polymerization was carried out under static conditions without dynamic solution flow. A constant potential of 0.8 V (relative to the silver / silver chloride quasi-reference electrode) was applied for 60 minutes (due to the slow static polymerization reaction, the time needed to be extended to ensure polymer thickness). After polymerization, the electrodes were statically immersed in dilute nitric acid solution for 4 hours for template agent elution.

[0060] Cobalt ion detection: A sample solution containing the cobalt ions to be tested was dropped onto the surface of the modified electrode and allowed to stand for 10 minutes for recombination. After cleaning, the cobalt ion concentration was calculated using the same differential pulse voltammetry parameters as in Example 1.

[0061] Comparative Example 2 (Traditional Static Polymerization and Pulsed Electrochemical Elution): Electrode Preparation: The polymerization process was the same as in Comparative Example 1, using static polymerization with a constant potential of 0.8V (relative to the silver / silver chloride quasi-reference electrode) applied for 60 minutes. After polymerization, the template agent was eluted using the same pulsed electrochemical elution parameters as in Example 1 (-0.5V, pulse width 50ms, repetition frequency 1Hz, total duration 5min, washing solution flow rate 1μL / min).

[0062] Cobalt ion detection: Same as Comparative Example 1, the sample solution was added dropwise and allowed to stand for 10 minutes for recombination, and the same detection method and parameters were used for detection.

[0063] Data comparison table (detection limit is the concentration corresponding to a signal-to-noise ratio of 3:1; relative standard deviation is the statistical value of 5 parallel experiments; response time is the time from sample contact with the electrode to the detection of a stable signal; selectivity coefficient is obtained by comparing the same concentration of Co...) 2+ with Ni 2+ The peak current ratio is calculated as follows:

[0064] Examples 1-5 employed microfluidic dynamic polymerization, with polymerization times of 10-30 minutes, significantly shorter than the 60 minutes of Comparative Examples 1 and 2. This was due to the continuous replenishment of reactants and removal of byproducts by the dynamic solution flow, thus accelerating the polymerization reaction. Regarding elution, the elution time in the examples was 5-15 minutes, while Comparative Example 1 required 240 minutes for static chemical elution, demonstrating that pulsed electrochemical elution significantly improved efficiency. Although Comparative Example 2 used pulsed elution to shorten the time, static polymerization itself is inefficient, and the overall preparation cycle was still longer than that of the examples.

[0065] The detection limit of the example was 0.008-0.02 μM, significantly lower than that of Comparative Example 1 (0.15 μM) and Comparative Example 2 (0.08 μM), indicating that the imprint sites formed by dynamic polymerization are uniform and highly accessible, thus improving detection sensitivity. The relative standard deviation of the example was 1.8%-3.2%, much lower than that of Comparative Example 1 (12.5%) and Comparative Example 2 (8.6%), demonstrating that the combination of dynamic polymerization and pulse elution significantly improves electrode reproducibility.

[0066] The response time of the examples was 15-32 minutes, shorter than 35 minutes in Comparative Example 1 and 30 minutes in Comparative Example 2, because dynamic recombination promoted the binding of the analyte ion to the imprinted site. The selectivity coefficient of the examples was 85-112, higher than 45 in Comparative Example 1 and 62 in Comparative Example 2, indicating that the quality of the imprinted site optimized by dynamic polymerization enhanced the specific recognition of cobalt ions.

[0067] Example 5, due to its integrated temperature control module and optimized reaction parameters, exhibited the lowest detection limit, smallest relative standard deviation, and highest selectivity coefficient, demonstrating that precise control of the reaction environment (such as temperature) and optimization of reaction parameters (such as monomer concentration, potential, and flow rate) can further improve detection performance. Comparative Example 2, although improving the elution method, did not address the fundamental defects of static polymerization, and its performance remained inferior to Example 5, proving that microfluidic dynamic polymerization is key to improving the performance of ion-imprinted polymer-modified electrodes.

[0068] In summary, the microfluidic dynamic electrochemical polymerization and pulsed electrochemical elution method of the present invention is superior to traditional methods in terms of polymerization efficiency, elution efficiency, detection sensitivity, reproducibility, response speed and selectivity, providing an efficient and reliable solution for cobalt ion detection.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting cobalt ions based on an ion-imprinted polymer-modified electrode, characterized in that, Includes the following steps: A. The preparation stage of the modified electrode, the preparation stage including: A1. Construct a microfluidic reaction system, which consists of a microfluidic chip, a high-precision liquid delivery module, and an electrochemical workstation; the microfluidic chip integrates at least one working electrode, one counter electrode, and one quasi-reference electrode. A2. Prepare and deliver a precursor solution, the precursor solution comprising a functional monomer solution, a template agent solution, and an electrolyte solution; the functional monomer solution, the template agent solution, and the electrolyte solution are synchronously injected into the microchannels of the microfluidic chip at a preset precise flow rate through the high-precision liquid delivery module; A3. Dynamic electrochemical polymerization is performed. While the precursor solution continuously flows over the surface of the working electrode, the electrochemical workstation applies a constant potential to the working electrode, causing the functional monomer to undergo oxidative polymerization on the surface of the working electrode to form an ion-imprinted polymer modification layer, and causing the template agent cobalt ions to be dynamically embedded or adsorbed into the ion-imprinted polymer network. A4. Perform pulsed electrochemical elution. After the dynamic electrochemical polymerization is completed, the electrochemical workstation applies a pulsed potential to the modified working electrode to achieve rapid and efficient elution of the template agent cobalt ions. B. The electrochemical detection stage of cobalt ions, wherein the detection stage includes: B1. Introduce the sample to be tested and rebind it. The sample solution containing the cobalt ions to be tested is injected into the microchannel through the high-precision liquid delivery module and allowed to remain on the surface of the eluted ion-imprinted polymer-modified electrode for a period of time to allow the cobalt ions to be tested to selectively bind to the imprinted sites. B2. Perform electrochemical signal detection. After the cobalt ions to be tested have been re-bound, the electrochemical workstation performs electrochemical measurements on the working electrode, detects the redox peak current associated with the cobalt ions bound to the imprinted sites, and quantitatively analyzes the concentration of cobalt ions in the sample based on the peak current.

2. The cobalt ion detection method according to claim 1, characterized in that, The microfluidic reaction system: The microfluidic chip adopts a multilayer composite structure, and its substrate is borosilicate glass. The surface of the substrate is formed with a microchannel array of precise geometric dimensions through photolithography and wet etching processes. The microfluidic chip is isolated from the external environment by a sealing structure, which is a polydimethylsiloxane cover plate that is thermo-pressed or plasma-bonded to the substrate. The high-precision liquid delivery module consists of multiple independently controlled micro-injection pumps.

3. The cobalt ion detection method according to claim 2, characterized in that, The electrodes integrated inside the microfluidic chip: The working electrode is a 100 nm thick gold thin film electrode formed at the bottom of the microchannel using a magnetron sputtering deposition process. The effective reaction area of ​​the gold thin film electrode is precisely defined by a 200 nm thick silicon nitride insulating layer. 2 ; The counter electrode is a 100 nm thick platinum thin film electrode formed in the microchannel by a process similar to sputtering. The quasi-reference electrode is a silver / silver chloride electrode formed on the chip by a silver chloride electroplating process.

4. The cobalt ion detection method according to claim 1, characterized in that, In the preparation and delivery of precursor solutions: The functional monomer solution is a solution of o-phenylenediamine in deionized water or a buffer solution, and the functional monomer solution is prepared in an oxygen-free environment filled with high-purity nitrogen. The template agent solution is a solution of cobalt(II) chloride hexahydrate in the same solvent; The electrolyte solution is a 0.1M phosphate buffer solution, which is prepared from disodium hydrogen phosphate and sodium dihydrogen phosphate. Before the polymerization reaction begins, the microchannels are first pre-cleaned with the electrolyte solution to ensure the cleanliness and uniformity of the internal environment of the channels; Subsequently, the functional monomer solution, the template agent solution, and the electrolyte solution are synchronously injected into the microchannel through the high-precision liquid delivery module at a total flow rate controlled within the range of 5 μL / min to 10 μL / min, forming a stable laminar flow mixture and continuously updating it.

5. The cobalt ion detection method according to claim 1, characterized in that, In the dynamic electrochemical polymerization: The electrochemical workstation applies a constant potential to the working electrode in the range of 0.8V to 1.2V.

6. The cobalt ion detection method according to claim 5, characterized in that, During the dynamic electrochemical polymerization process: The functional monomer is o-phenylenediamine, which undergoes oxidative polymerization under constant potential to form a poly(o-phenylenediamine) network. The poly(o-phenylenediamine) network contains multiple nitrogen atoms, which can form stable coordination with cobalt ions.

7. The cobalt ion detection method according to claim 1, characterized in that, During pulsed electrochemical elution: After the dynamic electrochemical polymerization is completed, the microchannel is first thoroughly cleaned with a pure electrolyte solution to remove residual unpolymerized monomers and free template agents from the microchannel; Subsequently, the electrochemical workstation applies a pulsed potential to the modified working electrode, the pulsed potential ranging from -0.5V to -0.8V; The pulse potential width is 50 ms to 150 ms; the pulse repetition frequency is 1 Hz to 5 Hz; and the total duration of the pulsed electrochemical elution process is 5 min to 15 min. During the pulsed electrochemical elution process, a cleaning solution is continuously introduced into the microchannel at a low flow rate to promptly remove the eluted template agent from the electrode surface and prevent its re-adsorption.

8. The cobalt ion detection method according to claim 7, characterized in that, During pulsed electrochemical elution: The negative pulse potential induces transient conformational changes or local charge state changes in the poly(o-phenylenediamine) matrix.

9. The cobalt ion detection method according to claim 1, characterized in that, In electrochemical signal detection: After recombination is completed, the microchannel is thoroughly cleaned again with a pure electrolyte solution to remove unbound cobalt ions and non-specific adsorbed substances in the sample matrix. Subsequently, the electrochemical measurement method is differential pulse voltammetry or square wave voltammetry, so as to effectively eliminate the interference of charging current on Faraday current by superimposing pulse signals; The measurement parameters of the differential pulse voltammetry or square wave voltammetry include: potential scan range from +0.2V to -0.5V, pulse amplitude of 50mV, pulse width of 50ms, scan rate of 20mV / s, and sampling interval of 5ms; During the potential scan, the redox peak current associated with cobalt ions bound to the imprinted sites is detected, with the typical reduction peak potential of the cobalt ions typically appearing between -0.1V and -0.3V. The electrochemical workstation acquires, processes, and analyzes the detected current signal in real time, and calculates the accurate concentration of cobalt ions in the sample to be tested using a pre-established calibration curve.

10. The cobalt ion detection method according to claim 1, characterized in that, The microchannels of microfluidic chips are designed in a serpentine or spiral structure; The microfluidic reaction system further integrates a temperature control module, which is a miniature temperature controller based on the Peltier effect.

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