An experimental teaching device based on electrochemical detection

Abstract

The present invention discloses an experimental teaching device based on electrochemical detection, which is characterized in that an electrode fixing unit, a detection unit, a control unit, a sensor and a circulation cell are integrated into a miniaturized electrochemical sodium ion concentration detection teaching device, wherein the detection unit receives a sensor signal to realize signal acquisition of a sample; the control unit controls the detection unit to acquire an ion-selective sensor signal to complete electrochemical detection; the circulation cell controls the electrode modification reagent or the reagent to be detected to cover a specified electrode according to different experiments, and controls the sample detection during the experimental process. Compared with the prior art, the present invention has a simple structure, can realize the interaction of multidisciplinary experimental content, cultivate students' learning interest and innovative consciousness, make up for the internal fragmentation of knowledge in primary and secondary education, and the shortcomings of single experimental operation, solve the problems of high sample consumption, bulky instruments, and complicated operations, and has good commercial application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical detection equipment, in particular to a portable miniaturized potential-type electrochemical sodium ion concentration detection teaching device.

[0002] Chemistry textbooks cover the principles of electrochemistry, but their focus tends to be theoretical, hindering students' mastery of common electrochemical detection techniques. To strengthen this foundation, ensure the full implementation of the required experiments in the curriculum, and effectively address the trend of neglecting experimental instruction, we must continuously incorporate cutting-edge scientific knowledge and the latest technological advances into experimental instruction. We must enrich the content, improve the methods, and prioritize effectiveness. This will strengthen students' practical skills, contextual experience, exploration, personal understanding, and creativity. We will focus on improving students' observational, hands-on, creative thinking, and teamwork skills, fostering their interest, innovative spirit, scientific literacy, and strong willpower. Electrochemistry experiments offer a wide range of methods and are simple to use, stimulating students' interest, practical skills, and innovative abilities. Furthermore, as a branch of chemistry, electrochemistry extends beyond chemistry to encompass a wide range of disciplines, including chemistry, biology, and physics. This allows students to more easily integrate these diverse areas of knowledge during experiments and cultivates their comprehensive practical skills.

[0003] Electrochemical sensing technology is an emerging discipline that has grown from the interpenetration of technologies from multiple disciplines, including chemistry, physics, biology, medicine, and electronics. Electrochemical sensors feature high sensitivity, rapid analysis speed, online continuous monitoring, and low instrument cost, making them widely used in fields such as environmental monitoring, life sciences, biomedicine, and food safety. Electrochemical sensing devices primarily consist of two integrated components: a sensor element and an electronic circuit element. The sensor element is a sensor component with functionalized electrodes that converts the analyte concentration into an electrical signal; the electronic circuit element processes, calculates, and transmits these signals for easy reading by terminal devices. Because electrochemical detection circuit design requires fewer components and the overall circuit complexity is relatively low, the electrochemical sensing element can be easily miniaturized and lightweight. The advantages of electrochemical detection technology in the field of ion detection have been widely recognized.

[0004] Ion-selective electrodes are a classic potentiometric analysis technique. The polymer ion-selective membrane, together with the internal filling solution and the internal reference electrode, forms the indicator electrode of the ion-selective electrode detection system. Through a loop system formed with the external reference electrode, direct detection of the target ion activity is achieved. When the ion-selective electrode is immersed in the ion solution to be measured, only the ion to be measured is allowed to enter the interior of the ion-selective sensitive membrane, while other ions are excluded from the membrane. Since the ion to be measured is charged, the ion to be measured will be unevenly distributed in the polymer membrane / aqueous phase during the process of entering the membrane phase, thereby generating an interphase potential. Since the internal filling solution contains a target ion solution with a certain activity, the internal potential of the polymer membrane remains constant. By directly measuring the potential of the ion-selective electrode, the activity of the target ion in the solution to be measured can be indirectly calculated.

[0005] Existing electrochemical detection devices are expensive, complex to operate, and difficult to understand, resulting in high sample consumption, bulky instruments, and tedious operations. We are designing a comprehensive experimental educational device based on electrochemical detection principles, tailored to the needs of primary and secondary education and the life sciences, and designed to integrate physical and electrochemical detection into chemical reaction experiments. This device will address the current limitations of simple experimental procedures and enhance and cultivate students' learning interest and innovative awareness. Summary of the Invention

[0006] The purpose of the present invention is to provide an experimental teaching equipment based on electrochemical detection to address the deficiencies of the existing technology. The invention adopts comprehensive experimental education equipment integrating physical and electrochemical detection, and adopts an integrated design for the electrode fixing unit, detection unit, control unit, ion selective sensor and microfluidic flow cell. The experimental teaching instrument combines the characteristics of primary and secondary school education and is oriented to the needs of the life field. Based on the electrochemical detection principle and chemical reaction experiment, it can be used for sodium ion concentration detection, making up for the shortcomings of the current knowledge fragmentation and single experimental operation in primary and secondary school education. The teaching instrument has a simple structure, can realize the interaction of multidisciplinary experimental content, cultivate students' learning interest and innovative consciousness, can be widely used in the detection of sodium ion concentration in human sweat, has good sensitivity, convenient detection, and can realize human health monitoring anytime and anywhere. At the same time, it solves the problems of high sample consumption, bulky instruments and complicated operations in traditional human sweat sodium ion concentration monitoring, and has good commercial application prospects.

[0007] The object of the present invention is achieved as follows: an experimental teaching device based on electrochemical detection, characterized in that the experimental teaching device includes: an electrode fixing unit, a detection unit, a control unit and a sensing unit (ion selective electrode), the ion selective electrode is connected to the electrode fixing unit by means of a plug-in card; the ion selective electrode and the detection unit are connected with the electrode fixing unit as an intermediary; the control unit includes: a signal conditioning module and a central processing module.

[0008] The electrode fixing unit and detection unit adopt an integrated design, integrating multiple functions such as electrode fixing, electrochemical detection and electrode signal acquisition into a small electrochemical device. The electrode fixing unit and detection unit are made of 3D printed resin material as a whole. The front end is the electrode fixing part, which is equipped with a card slot and electrode lead. During the experiment, the prepared ion-selective electrode is inserted into the electrode fixing hole. At this time, the working electrode, reference electrode, and auxiliary electrode of the ion-selective electrode can be connected to the electrochemical detection circuit through the electrode contacts installed in the hole. The electrochemical detection circuit is connected to the control unit. Through the signal conditioning module and the central processing module, the electrochemical reaction on the surface of the ion-selective electrode is controlled, and the open circuit voltage-time curve of a sample is quickly detected.

[0009] Furthermore, this experimental teaching equipment connects the various interfaces of the signal amplification circuit in the signal conditioning module to the surface of the shell to form a manual operation interface, which mainly includes: power switch, reference electrode voltage hole (V 参 )、range input hole (Vi), range selection hole a (Vi 1-4 )、Range selection hole b(Vo 1-4 ), voltage signal output port (Vo), ground port (GND), each port can be connected with a banana wire. The reserved holes in the manual operation interface are for students to operate. + Solution, students can manually select the range, this experimental teaching instrument provides four range options, range 1: no voltage amplification, detection range of -0.7v to 0.7v; range 2: voltage amplification 4.7 times, detection range of -0.15v to 0.15v; range 3: voltage amplification 10 times, detection range of -0.07v to 0.07v; range 4: voltage amplification 100 times, detection range of -0.007v to 0.007v. The range can be selected by connecting the range input hole Vi and the range selection hole Vi through a banana wire. 1-4 Connect any hole of Vo and Vo 1-4 This can not only exercise students' hands-on ability, but also allow them to learn the principles of electrochemical detection more deeply. Students can also use a voltmeter to measure the voltage signal output hole (Vo) and the reference electrode voltage hole (V 参 ) to verify whether the range is selected correctly. The value of Vo can be compared with the data detected by the host computer to verify the detection accuracy of the experimental teaching instrument. When the experimental teaching instrument does not perform electrochemical detection, students can input the voltage signal into the hole (V 参) to a voltage source, select a range to amplify the voltage, and use a voltmeter to measure the voltage at the voltage signal output port (Vo). This allows you to conduct physics and electrochemistry experiments, as well as familiarize yourself with circuit principles during instrument adjustments, making the device versatile.

[0010] The control unit is responsible for coordinating the connection between the signal conditioning circuit, the detection unit, and the central processing module, controlling the start, pause, continue, and stop steps of the experiment in real time, obtaining the time-voltage curves of sodium ion solutions with multiple concentrations during the detection process, and obtaining the relationship between concentration and voltage based on the time-voltage curves. Finally, based on this relationship, the sodium ion concentration of the solution to be tested can be measured and calculated.

[0011] The preparation method of the ion-selective electrode comprises the following specific steps:

[0012] Select a suitable three-electrode system as the basic material for the sodium ion selective electrode;

[0013] 2) The electrode was modified with gold nanoparticles according to actual needs. Sodium ion carrier X, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (Na-TFPB), and dioctyl sebacate (DOS) were dissolved in tetrahydrofuran (THF) in sequence. The mixture was stirred with a vortex mixer for 5 minutes and then ultrasonically vibrated for 30 minutes to completely dissolve.

[0014] 3) adding a high molecular weight polymer material to the above solution and stirring with a vortex mixer to dissolve it to obtain a sodium ion selective membrane solution;

[0015] 4) Pass the ion-selective membrane solution onto the surface of the gold electrode of the working electrode and allow it to dry naturally at room temperature to obtain a sodium ion-selective electrode.

[0016] 5) Prepare a membrane to protect the reference electrode potential. Dissolve PVB and NaCl in methanol to prepare a mixed solution. Pass the mixed solution onto the Ag / AgCl reference electrode and dry it at room temperature.

[0017] The electrode nano-gold modification in step 2) specifically includes: fixing the nano-gold on the surface of the gold film using existing laboratory equipment before preparing the sensitive film, or mixing the nano-gold into the reagent for preparing the sensitive film, and the nano-gold is covered on the surface of the gold film along with the sensitive film.

[0018] The sodium ion carrier X in step 2) is a 4-tert-butylcalix[4]arene-tetraethyltetraacetate organic compound that has the ability to selectively recognize sodium ions and can extract sodium ions from the solution (water) interface into the polymer sensitive membrane and bind to the target ions very quickly. This compound is a key carrier for ion exchange on the electrode surface; the Na-TFPB is a sodium ion exchanger that mainly promotes the sodium ion exchange process between the ion selective membrane and the aqueous solution, ensures a smooth polymerization process, and improves the conductivity of the ion selective membrane; the DOS is a plasticizer that can improve the ion The plasticity of the selective membrane enhances the fluidity of the ion-exchangeable components in the membrane, thereby improving the selectivity and detection limit of the selective membrane for the detected ions to a certain extent; the tetrahydrofuran is an organic solvent, mainly used as a solvent to provide a liquid environment to dissolve various materials for making the sodium ion selective electrode membrane; the reagent amount of the sodium ion carrier X is preferably 0.005-0.0020g; the reagent amount of the Na-TFPB is preferably 0.0002-0.0010g, the reagent amount of the DOS is preferably 0.03-0.07g, and the reagent amount of the THF is preferably 0.5-1 mL.

[0019] The high molecular weight polymer material in step 3) is a matrix material having good mechanical properties and good chemical stability, and is therefore used as a polymer substrate for an ion-selective membrane. The high molecular weight polymer material includes polyacrylate, polybutylacrylate, polyurethane, polysiloxane or polystyrene, preferably polyvinyl chloride (PVC); the reagent amount of the PVC is preferably 0.02 to 0.05 g.

[0020] In step 3), PVC is dissolved last to avoid excessive viscosity of this material affecting the dissolution of other materials.

[0021] The sodium ion selective membrane solution prepared in step 3) needs to be vacuum-sealed after preparation and stored in a freezer at a temperature of -4°C to 4°C away from light. The effect will not change significantly within 30 days.

[0022] The mixed solution in step 4) is used to prepare a PVB film wrapped with silver chloride. After being covered with the PVB film, the reference electrode has good ion stability. The reagent volume of the PVB is preferably 50-100 mg; the reagent volume of the NaCl is preferably 20-70 mg; and the reagent volume of the methanol is preferably 0.6-1 ml.

[0023] In step 4), the ion-selective membrane solution is dripped onto the surface of the gold electrode of the working electrode. A technician in this field uses a pipette to add a small amount of ion-selective membrane solution to the surface of the working electrode multiple times, adding 2 to 5 ul each time, and dividing it into three times to avoid the center of the electrode being uncovered by the membrane.

[0024] The solution in step 4) and step 5) can be added dropwise using a circulation pool to ensure smooth coverage of the solution.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects and significant technical progress:

[0026] 1) Using a small ion-sensing electrode as the electrochemical sensing unit, due to the advantages of such electrodes being small in size, requiring less consumables in the ion-selective electrode modification process, requiring less sample and reagent consumption in the experiment, having a simple detection process, fewer operating steps, high integration, and being able to detect in real time, the present invention can be used to perform electrochemical detection of trace sodium ions, thereby resolving the problems of high sample consumption, bulky instruments, and cumbersome operations in the prior art.

[0027] 2) It adopts a miniaturized, integrated electrochemical detection device with easy component installation, low material consumption, and easy portability, allowing samples to be tested anytime and anywhere.

[0028] 3) The surface of the working electrode is modified with nanomaterials, which greatly improves the electrode performance. By modifying the surface of the working electrode with graphene oxide or nano-gold by deposition, it is expected to improve the performance of the electrode, such as electrode conductivity, on the original basis, and some progress has been made. This electrode modification method can be effectively used to improve electrode performance.

[0029] 4) Based on the working principle of the ion-sensitive membrane, a sensitive membrane for sodium ion detection is produced, so that the sodium ion selective electrode designed by the present invention has excellent conductivity, sensitivity, and a good detection limit. For example, when the electrode of the present invention is used to detect a sodium chloride solution with a certain concentration gradient, its sensitivity is about 100mV / decade, and its detection limit is 1×10 -5 M, since the sodium ion content in human sweat will not be lower than this concentration, the present invention can be widely used in the detection of sodium ions in human sweat and has high accuracy.

[0030] 5) The electrochemical control section features easy operation, an excellent interface design, and comprehensive functionality. This control software allows mobile phone control of the electrochemical testing process, making it easier to conduct experiments anytime, anywhere. The communication signal is stable and has strong anti-interference capabilities. The entire control process requires minimal environmental stability, making it suitable for use in complex environments. Furthermore, this software allows for rapid setting of experimental parameters, data reception, and data display, facilitating real-time monitoring and observation of the experimental process.

[0031] 6) The electrochemical detection comprehensive experimental education equipment incorporates the concept of multidisciplinary cross-disciplinary thinking. In terms of electrochemical signal detection, circuit connection terminals are reserved for students to manually complete the wiring of the detection circuit, helping them understand the electrical principles in physics. In terms of chemical information detection, experiments are used to demonstrate the process of converting chemical ion concentration into electrical information, allowing students to gain a deeper understanding of chemical principles. Sodium is an essential constant element in the human body. Abnormal sodium ion concentration may induce hypertension and harm the central nervous system. Taking Na ion concentration detection as an example, students can understand the application of this technology in biology. Electrochemical electrodes are sensors for signal acquisition, and sensors are the source of information technology. Through experiments, students can understand the connotation of modern information technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a structural diagram of the present invention;

[0033] Figure 2 This is a schematic diagram of the embedded circuit board structure;

[0034] Figure 3 This is a schematic diagram of the internal structure of the base of the device in Example 1;

[0035] Figure 4 This is a schematic structural diagram of the sodium ion electrode connector of Example 1;

[0036] Figure 5 This is a schematic diagram of the internal structure of the top cover of the device in Example 1;

[0037] Figure 6 This is a schematic diagram of the appearance design of the device in Example 1;

[0038] Figure 7 Schematic diagram of the flow cell structure of Example 1;

[0039] Figure 8 This is a layered schematic diagram of the ion-selective electrode produced in Example 1;

[0040] Figure 9 This is an operational flow chart of Example 1;

[0041] Figure 10 This is a flow chart of ion concentration detection in Example 1;

[0042] Figure 11 This is the Na ion gradient experimental curve diagram of Example 1;

[0043] Figure 12 This is a linear relationship diagram of the detection limit of the present invention. Implementation Method

[0044] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention. Example

[0045] See Figure 1 The present invention consists of an electrode fixing unit, a detection unit, a control unit, an ion selective sensor and a microfluidic flow cell. The ion selective sensor converts chemical signals into detectable electrical signals; the electrode fixing unit fixes the ion selective sensor, that is, the ion selective electrode, on the device to ensure the stability of the experiment; the detection unit is an electrochemical detection circuit, including signal acquisition, which collects the electrical signals converted by the ion selective sensor and sends them to the control unit; the control unit includes: a signal conditioning module, a central processing module and a communication interface; the electrochemical detection circuit first collects the signals obtained by the three-electrode sodium ion sensor, and completes signal acquisition, processing and transmission through the signal conditioning module and the central processing module; the central processing module communicates and interacts with the computer / mobile phone through the communication interface; the control unit uses a computer or mobile phone to communicate and interact with the detection unit through the software operation interface. When solutions of different concentrations need to be detected, the control unit can pause and continue the experiment, thereby continuously detecting solutions of different concentrations.

[0046] See Figure 2 The embedded circuit board 1 adopted by the present invention mainly includes: circuit board fixing holes 2, 3, and 4, a circuit ground terminal block 5, a power input terminal block 6, a power switch terminal block 7, a power module 8, a central processing module 9, a digital-to-analog conversion module 10, a digital-to-analog conversion output terminal block 11, a detection system chipset 12, an auxiliary electrode terminal block 13, a working electrode terminal block 14, a reference electrode terminal block 15, a signal conditioning module 16, a range input terminal block 17, a range-a terminal block 18, a range-b terminal block 19, a range-two a terminal block 20, a range-two b terminal block 21, a range-three a terminal block 22, a range-three b terminal block 23, a range-four a terminal block 24, a range-four b terminal block 25, a signal output terminal block 26, an analog-to-digital conversion module 27, a serial communication chip 28, a serial port terminal block 29, and a Bluetooth module 30.

[0047] The power supply module 8 is responsible for supplying power to all parts of the circuit; the central processing module 9 is responsible for signal storage and communication with the host computer; the digital-to-analog conversion module 10 converts digital signals into analog signals, and can measure whether the converted voltage signal meets the expected requirements through the digital-to-analog conversion output terminal 11; the signal conditioning module 16 is responsible for amplifying and filtering the collected electrical signals to improve detection accuracy; the analog-to-digital conversion module 27 converts electrical signals into digital signals that can be recognized by the central processing module 9 and stores data; the communication module 28 is a serial communication chip, and coordinates with the central processing module 9, and can use serial communication and Bluetooth communication to transmit data to the host computer for drawing.

[0048] See Figure 3 The embedded circuit board 1 is fixed to the base 31 of the sodium ion detection device through the circuit board fixing hole. The power input hole 38 and the RS232 serial port 39 are respectively fixed on the side of the sodium ion detection device base 31, and one end of the power input hole 39 is connected to the power input terminal block 6 using a wire. At this time, the power cord is inserted into the power input hole 6, and the other end can power the device. One end of the RS232 serial port 39 is connected to the serial port terminal block 29, and the other end is connected to the host computer to complete the interaction between the computer and the device. The sodium ion selective electrode 71 can be inserted into the sodium ion selective electrode interface 40 to realize the conversion of the sensor signal.

[0049] See Figure 4 The sodium ion electrode connector is the connection intermediary between the circuit and the sensor. The electrode contact 42 is fixed in the electrode contact fixing part 41. One end of the auxiliary electrode contact 43, the working electrode contact 44 and the reference electrode contact 45 are respectively in contact with the auxiliary electrode, the working electrode and the reference electrode of the sodium ion selective electrode 71. The other ends of the auxiliary electrode contact 43, the working electrode contact 44 and the reference electrode contact 45 are respectively connected to the auxiliary electrode terminal block 13, the working electrode terminal block 14 and the reference electrode terminal block 15 of the embedded circuit board 1 through wires to connect the sensor to the circuit, thereby realizing the device's collection of sensor signals.

[0050] See Figure 5, fix the electrode contact piece fixing piece 41 inside the top cover of the sodium ion detection device. In order to lead the amplifying circuit in the signal conditioning module 16 to the surface of the device, fourteen signal holes 54 to 67 and a power switch hole 53 are punched on the top cover of the sodium ion detection device. The device fixes the power switch button 68 in the power switch hole 53. Banana sockets 69 are installed in the fourteen signal holes. The other end of the power switch button 58 is connected to the power switch terminal block 7 of the circuit board through a wire. The banana socket of the digital-to-analog output hole 54 is connected to the digital-to-analog conversion terminal block 11 of the circuit board. The banana socket of the working electrode hole 55 is connected to the working electrode terminal block 14 through a wire. The banana socket of the reference electrode hole 56 is connected to the reference electrode terminal block 14 through a wire. The banana sockets of the range input hole 58 are connected to the range input terminal block 17 via a wire. The banana sockets of the range selection holes a59, 61, 63, and 65 are connected to the range terminal blocks a18, 20, 22, and 24, respectively, via wires. The banana sockets of the range selection holes b60, 62, 64, and 66 are connected to the range terminal blocks b19, 21, 23, and 25, respectively, via wires. The banana socket of the signal output hole 67 is connected to the signal output terminal block 26 via a wire. At this point, by connecting the banana sockets to the circuit, the voltage amplification circuit of the signal conditioning module 16 is transferred to the surface of the device, allowing manual operation, including circuit switching, signal measurement, and range selection. This enhances students' hands-on skills and helps them gain a deeper understanding of the detection process.

[0051] See Figure 6 Fasten the base and top cover of the sodium ion detection device tightly, aligning the base fixing holes 32, 33, 34, 35, 36, and 37 with the top cover fixing holes 47, 48, 49, 50, and 51. Secure them with M3 screws. Plug the power cord into the power input hole 38 and press the power switch button 58. The device can now be used normally for experiments. As a teaching device, a student operation interface is designed on the top cover of the device, allowing students to operate the instrument interface and gain a deeper understanding of the detection process. The interface mainly provides a practical operation and principle of voltage amplification. During the experiment, students can use banana wires 70 to connect the various interfaces according to the signal size and select the appropriate voltage amplification range.

[0052] The present invention can not only be used for sodium ion concentration detection experiments, but also for physical electrical experiments. Students can connect a certain voltage at the reference electrode interface, randomly select a range, and measure the voltage at the Vo interface at this time to calculate the amplification factor and understand the voltage amplification principle of the operational amplifier.

[0053] In order to optimize the overall process of electrode modification and electrochemical experiment, the flow pipe and control valve of the flow pool are used to accurately control the modification process. The present invention uses a three-electrode system, including: a working electrode 76, an auxiliary electrode 77, and a reference electrode 78. A PDMS flow pool 80 is made by casting after making a model. The flow pool includes: four flow ports (72, 73, 74, 75) and a flow pipe (79). Four valves 81, 82, 83, and 84 are set above the pipe near the flow port. During electrode modification and experiment, the flow direction of the solution is controlled by opening and closing the four valves to determine which electrode the solution passes through. The operation is simple and can be accurately controlled according to the reagent amount requirement. The coverage and flatness of the sensitive membrane are enhanced when the sensitive membrane is modified.

[0054] Furthermore, as previously explained, the banana sockets within each hole in the user interface are connected to the various terminal blocks on the embedded circuit board via wires. This allows students to manually operate the device and understand the principles of voltage amplification. Furthermore, when the device is not being used for experiments, the power supply should be turned off, and banana wire 70 should be used to connect reference electrode hole 56 to ground hole 57 to protect the circuit. When conducting electrochemical experiments, the banana wire between reference electrode hole 56 and ground hole 57 should be removed. Because each range has a different detection range, it is necessary to select the appropriate range. Range 1 does not amplify voltage, with a detection range of -0.7V to 0.7V; Range 2 amplifies voltage 4.7 times, with a detection range of -0.15V to 0.15V; Range 3 amplifies voltage 10 times, with a detection range of -0.07V to 0.07V; and Range 4 amplifies voltage 100 times, with a detection range of -0.007V to 0.007V. Students can first detect the voltage of the maximum concentration solution. When testing, they should first select range one for measurement, that is, use a banana wire to connect the range input hole 58 to the range one a selection hole 59, and the range one b selection hole 60 to the signal output hole 67. Insert the sodium ion selective electrode into the electrode interface 40, drip the maximum concentration solution, and finally select the appropriate range according to the voltage detected by the device. After the range is determined, students use banana wires to connect the range input hole 58 to the range one, two, three, and four a selection holes 59, 61, 63, and 65, and connect the range one, two, three, and four b selection holes 60, 62, 64, and 66 to the signal output hole 67. After the wiring is completed, the experiment can begin. During the experiment, students can use a voltmeter to measure the voltage value Vo of the signal output hole 67 and the voltage V of the reference electrode hole 56. 参The ratio of Vo can be used to verify whether the range is selected correctly. The value of Vo can be compared with the data detected by the host computer to verify the accuracy of the device's detection. The device can not only perform electrochemical sodium ion concentration detection experiments, but also physical electrical experiments, that is, connect the reference electrode hole 56 to the voltage source, select the appropriate voltage and range, calculate the amplified voltage value, use a multimeter to measure the voltage of the signal output hole, compare the calculated voltage with the measured voltage, and verify the range magnification. The right side of the operation interface also lists the voltage amplification principle in detail, allowing students to complete the integration from understanding the principle to actual operation, deepening their understanding of the experimental process. The device's operation interface can not only exercise students' hands-on operation skills, but also deepen students' understanding of the detection principle. The sodium ion detection device that can perform both chemical detection and physical electrical experiments has achieved multiple uses.

[0055] The working electrode in this embodiment has an unmodified surface and is covered with a selective membrane to form a sodium ion selective electrode for electrochemical detection of sodium ions.

[0056] See Figure 7 The preparation method of the sodium ion selective electrode comprises the following specific steps:

[0057] The Au-Au-Ag / AgCl three-electrode system was selected as the basic material for the sodium ion selective electrode;

[0058] 2) Dissolve 0.005-0.0020 g of sodium ion carrier X, 0.0002-0.0010 g of Na-TFPB, and 0.03-0.07 g of DOS in 0.5-1 mL of tetrahydrofuran, stir with a vortex mixer for 5 minutes, and then ultrasonically vibrate for 30 minutes to completely dissolve them. The sodium ion carrier X is 4-tert-butylcalix[4]arene-tetraethyltetraacetate;

[0059] 3) Add 0.02-0.05 g of PVC to the above solution and stir with a vortex mixer to dissolve it to obtain an ion-selective membrane solution;

[0060] 4) Add 3-5 μl of the ion-selective membrane solution three times onto the surface of the gold electrode of the working electrode. Allow it to dry naturally at room temperature to obtain a sodium ion-selective electrode.

[0061] See Figure 8 The specific structure of the ion-selective electrode is divided into three layers, which are, from bottom to top, a working electrode 76, gold nanoparticles 86, and a sodium ion sensitive membrane 85. The flow channel 79 covers the structure, and the materials required for electrode modification are deposited on the surface of the working electrode multiple times through the flow channel 79 to realize the preparation of the ion-selective electrode.

[0062] Modification of the reference electrode: Dissolve 50-100 mg of PVB and 20-70 mg of NaCl in 0.6-1 ml of methanol to prepare a mixed solution, apply the mixed solution to the Ag / AgCl reference electrode, and dry it at room temperature to obtain a modified reference electrode.

[0063] See Figure 9 In the sodium ion electrochemical detection experiment, after the sodium ion selective electrode is manufactured and the reference electrode is modified, a NaCl solution with a certain concentration gradient is used to test the sensitivity, detection limit, gradient display, etc. of the electrochemical sensor. The specific steps are as follows:

[0064] 1) Prepare NaCl solutions with concentrations of 8mM, 16mM, 32mM, 64mM, and 128mM using deionized water and solid NaCl reagent. -8 The NaCl solution with a concentration of 1 M to 1 M was thoroughly mixed using a mixer and used as a sample reagent for testing.

[0065] 2) Select the open-circuit voltage-time curve function for the experimental parameter settings. Set the following parameters: Upper voltage limit: 0.5V, Lower voltage limit: -0.5V, Acquisition rate: 1s, and Run time: 250s. Complete the pre-experimental parameter settings. Divide the run time into five segments, replacing the NaCl solution every 50s. Add 100µl of NaCl solution (8mM, 16mM, 32mM, 64mM, and 128mM) in ascending order of concentration. Run one experimental cycle, collect the open-circuit voltage-time curves for the five NaCl solution concentrations, and save the data.

[0066] 3) Select the open circuit voltage-time curve function in the experimental parameter setting section, set the following parameters: upper limit voltage: 0.5V, lower limit voltage: -0.5V, acquisition rate: 1s, run time: 450s, and complete the parameter setting before the experiment. Divide the run time into nine sections, and replace the NaCl solution every 50s. The NaCl solution (10 -8 The order of adding the reagents (100 μl each time) was from low to high concentration. The open circuit voltage-time curves of the nine concentrations of NaCl solutions were collected and the relevant data were saved.

[0067] See Figure 10The ion-selective electrode prepared in the example was used to detect standard gradient curves of NaCl solutions with concentrations of 8 mM, 16 mM, 32 mM, 64 mM, and 128 mM, and the sensitivity of the ion-selective sensor was calculated using a binary regression equation. The flow of this calculation method is as follows: In order to reduce data dispersion or density caused by excessively large values, without affecting the data change trend, the logarithm of the sodium ion concentration lg[Na+] was taken as the horizontal axis, and the potential value E was taken as the vertical axis to show the change pattern of E with the change of lg[Na+]. The concentrations of NaCl solutions used in this experiment are 8mM, 16mM, 32mM, 64mM, and 128mM, and the corresponding lg[Na+] values are 0.903mM, 1.204mM, 1.505mM, 1.806mM, and 2.107mM. Five numerical points are taken according to the lg[Na+] and E corresponding to the five concentrations of NaCl solutions. The standard equation E=0.09838lg[Na+]-0.08866 is obtained by fitting the numerical points. That is, the standard curve is represented by this binary regression equation. The sensor sensitivity is 98.38mV / decade, which has high sensitivity. At the same time, the linear relationship of the response signal is obvious, indicating that the experimental stability is good.

[0068] See Figures 11 and 12 The ion selective electrode prepared in this embodiment can detect 10 -8 The detection limit and linear interval diagram of the standard gradient curve of NaCl solution with a concentration of mM-1mM are shown in the figure. It can be seen from the figure that the detection limit of the ion selective sensor is approximately 1×10 -4.3 M, the linear range is 1×10 -4 M to 1 M, which covers all possible concentrations of sodium ions in human sweat, indicating that the device can effectively detect the concentration of sodium ions in human sweat.

[0069] This embodiment designs a small electrochemical sensor device for sodium ion detection. This device can be widely used to detect sodium ion concentration in human sweat. It is convenient to detect, has a good sensitivity detection limit, and can realize human health monitoring anytime and anywhere. At the same time, it solves the problems of high sample consumption, bulky equipment, and complicated operation in traditional human sweat sodium ion concentration monitoring, and has good employment prospects.

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An experimental teaching device based on electrochemical detection, characterized in that: The electrode fixing unit, detection unit, control unit, ion selective sensor and microfluidic flow cell are integrated into a miniaturized teaching device for electrochemical sodium ion concentration detection. The ion selective sensor is connected to the electrode fixing unit in a plug-in manner, and the ion selective sensor is fixed by the electrode fixing unit; the detection unit is an electrochemical detection circuit, and is connected to the ion selective sensor through the electrode fixing unit as an intermediary, and receives the sensor signal of the ion selective sensor through the electrode lead to realize signal acquisition of the sample; the control unit is composed of a signal conditioning module and a central processing module, and the signal conditioning module is connected to the detection unit to control the detection unit to collect the ion selective sensor signal, and complete circuit debugging and electrochemical detection respectively; the microfluidic flow cell is arranged directly above the ion selective sensor, and controls the electrode modification reagent or the reagent to be detected to cover the specified electrode according to different experiments, thereby controlling the sample detection during the experiment; The microfluidic flow cell is composed of a PDMS layer cast from PDMS material and a control valve. The PDMS layer includes: a flow channel and multiple flow holes. The flow channel is designed according to the shape and position of the working electrode, auxiliary electrode, and reference electrode, and completely covers the electrode reaction area. The control valve is located above the flow channel, and the opening and closing of the control valve are used to precisely control the flow of reagents through the designated electrode. The multiple flow holes introduce electrode modification reagents or reagents to be detected into the flow cell, and the control valve controls the electrode modification reagents or reagents to be detected to cover the designated electrodes according to different experimental requirements, thereby achieving static modification or flow detection. The signal conditioning module has the function of signal amplification, and this is achieved by setting up multiple interfaces to connect the circuit to the surface of the device casing to form a manual operation interface. The manual operation interface includes: a power switch, a reference electrode voltage hole, a range input hole, a range selection hole a, a range selection hole b, a voltage signal output hole and a grounding port. During the experiment, the holes are connected by wires, and electrical testing is completed on the manual operation interface.

2. The experimental teaching equipment based on electrochemical detection according to claim 1, characterized in that: The preparation of the ion selective sensor specifically includes the following steps: 1) Selecting the Au-Au-Ag / AgCl three-electrode system as the basic material for the sodium ion selective electrode; 2) Dissolve 0.005-0.0020 g of sodium ion carrier X, 0.0002-0.0010 g of Na-TFPB, and 0.03-0.07 g of DOS in 0.5-1 mL of tetrahydrofuran, stir for 5 minutes, and then ultrasonically vibrate for 30 minutes to completely dissolve them. The sodium ion carrier X is 4-tert-butylcalix[4]arene-tetraethyltetraacetate; 3) Add 0.02-0.05 g of PVC to the above solution and stir to dissolve it to obtain an ion-selective membrane solution; 4) Add 3 to 5 μL of the ion-selective membrane solution to the surface of the working electrode three times and allow to dry naturally at room temperature to prepare a sodium ion-selective electrode; 5) Prepare a mixture by dissolving 50-100 mg of PVB and 20-70 mg of NaCl in 0.6-1 mL of methanol. Apply the mixture to an Ag / AgCl reference electrode and dry at room temperature.

3. The experimental teaching equipment based on electrochemical detection according to claim 1 or claim 2, characterized in that: The working electrode, auxiliary electrode and reference electrode of the ion selective sensor are designed to be rectangular in shape to ensure that the flow channel of the microfluidic flow cell arranged above the ion selective sensor completely covers the entire electrode.

4. The experimental teaching equipment based on electrochemical detection according to claim 2, characterized in that: The working electrode is modified with a layer of nano-gold particles for improving the conductivity and sensitivity of the sensor.

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