Salt solution ph detection device and method based on salt difference conversion

Abstract

The application relates to the field of microfluidic technology, and particularly provides a salt solution pH detection device and method based on salt difference conversion. The device comprises a reference cavity, an ion exchange membrane, a detection cavity, electrodes, a data acquisition circuit board and a picoammeter; the reference cavity and the detection cavity are connected through the ion exchange membrane, one electrode is inserted into each of the detection cavity and the reference cavity, the two electrodes are connected through the data acquisition circuit board and the picoammeter in sequence, and the detection data is displayed in real time through the data acquisition circuit board; the ion exchange membrane is constructed by using a functionalized nanochannel array with pH response; the data acquisition circuit board comprises a microprocessor, a lithium battery and an OLED screen; the pH difference of the salt solutions on the two sides of the membrane is converted into an ionic current which can reflect the pH level, the ionic current signal is converted into the pH value of the salt solution to be detected through the data acquisition circuit board, and the pH value is displayed in real time through the OLED screen; the device has a wide detection range, high detection sensitivity and can detect the pH in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microfluidic technology, and particularly relates to a salt solution pH detection device and method based on salt difference conversion. BACKGROUND

[0002] The measurement of solution pH is a key step in chemical and biological experiments. Common pH detection methods include point method and optical fiber detection method. Among them, the potential method is an electrochemical analysis method for determining the content of the measured substance in the solution by the relationship between the electrode potential and the concentration of the measured substance. The point method measures pH by using an electrode sensitive to hydrogen ions. The earliest point method uses a hydrogen electrode, but the hydrogen electrode has high requirements for the environment and low practical value. Currently, the most commonly used electrode is a glass electrode, which has high measurement accuracy and wide measurement range, but the electrode is easily broken and cannot be miniaturized. The optical fiber pH sensor has a pH-sensitive chemical substance inside, and has different spectral characteristics at different pH values. According to the characteristics of the light signal change, it can be divided into three types: light absorption, reflection and fluorescence. This detection method has high sensitivity and short response time, but it has high requirements for the quality of laser and is easily affected by environmental light, and the detection range is narrow and not suitable for wide use. Therefore, a method for detecting a wide range, high sensitivity and real-time pH detection is needed. SUMMARY

[0003] The present application provides a salt solution pH detection device and method based on salt difference conversion to solve the above problems.

[0004] The present application aims to provide a salt solution pH detection device based on salt difference conversion, characterized by comprising a reference cavity, an ion exchange membrane, a detection cavity, an electrode, a data acquisition circuit board and a picoammeter;

[0005] The reference cavity and the detection cavity are connected by the ion exchange membrane, and an electrode is inserted into each of the detection cavity and the reference cavity. The two electrodes are connected in sequence by the data acquisition circuit board and the picoammeter, and the detection data is displayed in real time by the data acquisition circuit board;

[0006] The reference solution is placed in the reference cavity, and the detection liquid is placed in the detection cavity;

[0007] The ion exchange membrane is constructed by using a functionalized nanochannel array with pH response;

[0008] The data acquisition circuit board comprises a microprocessor, a lithium battery and an OLED screen, and the lithium battery supplies power to the microprocessor and the OLED screen;

[0009] The electrode transmits the collected ion current to the microprocessor. The picoammeter obtains the correspondence between the pH of the test solution and the ion current. The correspondence is recorded by a program and processed by the microprocessor. The collected ion current signal is converted into a pH value and directly displayed on the OLED screen.

[0010] Preferably, the functionalized nanochannels are constructed by obtaining solid nanochannels based on anodic aluminum oxide through a two-step oxidation method, and then grafting a polyelectrolyte brush layer onto the inner surface of the solid nanochannels.

[0011] Preferably, the solid-state nanochannel is constructed using a two-step oxidation method, and the material used is aluminum.

[0012] Preferably, the polyelectrolyte brush layer is made of lysine.

[0013] Preferably, the thickness of the polyelectrolyte brush layer is 4–6 nanometers.

[0014] Preferably, the diameter of the nanochannel is 18-22 nanometers.

[0015] Preferably, the thickness of the ion exchange membrane is 9.5 to 10.5 micrometers.

[0016] Preferably, the microprocessor is based on the STM32 data acquisition system.

[0017] Another objective of this invention is to provide a method for detecting the pH of a salt solution based on salinity gradient conversion, using the aforementioned salt solution pH detection device based on salinity gradient conversion, with the following specific steps:

[0018] S1. Preparation of ion exchange membranes;

[0019] S2. The reference chamber and the detection chamber are connected by an ion exchange membrane. A 0.01M salt solution is placed in the reference chamber as a reference solution. The test solutions are placed in the detection chamber respectively. The relationship between the pH of the test solution and the ion current is obtained by the picoammeter.

[0020] S3. The corresponding relationship is recorded by the program, analyzed by the data acquisition circuit board, and converted into a specific value of the salt solution pH, which is then displayed on the OLED screen in real time.

[0021] Preferably, the functionalized nanochannels are prepared by the following method:

[0022] S101. Using aluminum as the material, a porous anodic aluminum oxide film is obtained through a two-step oxidation method, which yields a solid-state nanochannel.

[0023] S102. Graft the polyelectrolyte brush layer onto the inner surface of the solid nanochannel to construct a functionalized nanochannel.

[0024] Beneficial effects of this invention:

[0025] The present invention relates to a salt solution pH detection device and method based on salt difference conversion. By designing an ion exchange membrane to connect the detection chamber and the reference chamber, the pH difference of the salt solution on both sides of the membrane is converted into an ion current. The magnitude of the ion current reflects the pH level of the salt solution to be tested. The output ion current signal is converted into the pH value of the salt solution to be tested through a data acquisition circuit board and displayed in real time on an OLED screen. It has a wide detection range, high detection sensitivity, and can detect pH in real time. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a salt solution pH detection method based on salinity gradient conversion provided in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of a salt solution pH detection device provided in an embodiment of the present invention.

[0028] Figure 3 A schematic diagram of functionalized nanochannels provided for embodiments of the present invention.

[0029] Figure 4 The graph shows the relationship between different pH salt solutions and ion currents provided in the embodiments of the present invention.

[0030] Figure 5 The graph shows the relationship between different pH salt solutions and ion currents for silicon-based nanochannel detection provided in this embodiment of the invention.

[0031] Figure Labels

[0032] 1. Reference cavity; 2. Ion exchange membrane; 3. Detection cavity; 4. Electrode; 5. Data acquisition circuit board; 6. Picoammeter; 21. Functionalized nanochannel; 211. Nanochannel wall; 212. Polyelectrolyte brush layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0034] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices. Regarding directional descriptions, such as up, down, front, back, left, right, etc., indicating directions or positional relationships, these are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0035] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0036] This invention Figure 2 A salt solution pH detection device based on salinity gradient conversion is shown, including a reference chamber 1, an ion exchange membrane 2, a detection chamber 3, an electrode 4, a data acquisition circuit board 5, and a picoammeter 6;

[0037] The reference cavity 1 and the detection cavity 3 are connected by an ion exchange membrane 2. An electrode 4 is inserted into each of the detection cavity 3 and the reference cavity 1. The two electrodes 4 are connected in sequence by a data acquisition circuit board 5 and a picoammeter 6. The detection data is displayed in real time through the data acquisition circuit board 5.

[0038] A reference solution is placed in the reference chamber 1. The reference solution is a 0.01M salt solution; the salt solution is a NaCl solution with pH=7.

[0039] The detection chamber 3 is filled with the solution to be tested (salt solutions with the same concentration but different pH).

[0040] The ion exchange membrane 2 is constructed using a functionalized nanochannel 21 array, and the membrane thickness is 10 micrometers to reduce the impact of concentration polarization at the channel opening.

[0041] The functionalized nanochannel 21 is obtained by chemical modification inside the solid nanochannel. The inner wall of the nanochannel wall 211 of the solid nanochannel is modified by grafting a polyelectrolyte brush layer 212 to change the surface properties of the inner wall of the channel.

[0042] The solid nanochannels are made of aluminum and porous anodic aluminum oxide films are obtained through a two-step oxidation method. The diameter of the nanochannels is 20 nanometers.

[0043] The thickness of the polyelectrolyte brush layer 212 is d. m =5 nanometers, lysine was chosen as the material;

[0044] The data acquisition circuit board 5 includes a microprocessor, a lithium battery, and an OLED screen. The connection between the microprocessor, lithium battery, and OLED screen is such that the lithium battery powers the microprocessor and the OLED screen, the ion current collected by the electrode is transmitted to the microprocessor, and the pH value of the solution to be tested is displayed on the OLED screen.

[0045] The correlation between pH and ionic current for different salt solutions (test solutions) was obtained using the Pi-Ammeter 6, as shown in the figure. Figure 4 As shown; the relationship between the pH of the salt solution and the ion current is recorded by a program and processed by a microprocessor;

[0046] The microprocessor is based on an STM32-based data acquisition system, which converts the acquired ion current signal into a pH value and displays it directly on the OLED screen.

[0047] This invention provides a method for pH detection of salt solutions based on salinity gradient conversion, using the aforementioned apparatus, and the specific steps are as follows:

[0048] S1. Preparation of ion exchange membranes;

[0049] S2. The reference chamber and the detection chamber are connected by an ion exchange membrane. A 0.01M salt solution is placed in the reference chamber as a reference solution. The test solutions are placed in the detection chamber respectively. The relationship between the pH of the test solution and the ion current is obtained by the picoammeter.

[0050] S3. The corresponding relationship is recorded by the program, analyzed by the data acquisition circuit board, and converted into a specific value of the salt solution pH, which is then displayed on the OLED screen in real time.

[0051] The ion exchange membrane is constructed from a functionalized nanochannel array with pH response;

[0052] The ion exchange membrane has a thickness of 10 micrometers;

[0053] The functionalized nanochannels are prepared by the following method:

[0054] S101. Using aluminum as the material, a porous anodic aluminum oxide film is obtained through a two-step oxidation method, which yields a solid-state nanochannel.

[0055] S102. Graft the polyelectrolyte brush layer onto the inner surface of the solid nanochannel to construct a functionalized nanochannel.

[0056] The polyelectrolyte brush layer has a thickness of 5 nanometers and is made of lysine.

[0057] The polyelectrolyte brush layer undergoes protonation and deprotonation reactions, as shown below:

[0058]

[0059]

[0060] A volume charge density related to hydrogen ions will be generated within the polyelectrolyte brush layer, and the specific calculation formula is as follows:

[0061]

[0062] Therefore, the surface properties of solid nanochannels can be adjusted by changing the pH of the solution;

[0063] The salt solution in step S2 is a NaCl solution with pH = 7;

[0064] In step S3, the analysis is performed through a data acquisition circuit board, specifically through a microprocessor on the data acquisition circuit board.

[0065] Example 1

[0066] Figures 1-2 A salt solution pH detection device based on salinity gradient conversion is shown, including a reference chamber 1, an ion exchange membrane 2, a detection chamber 3, an electrode 4, a data acquisition circuit board 5, and a picoammeter 6;

[0067] The reference cavity 1 and the detection cavity 3 are connected by an ion exchange membrane 2. An electrode 4 is inserted into each of the detection cavity 3 and the reference cavity 1. The two electrodes 4 are connected in sequence by a data acquisition circuit board 5 and a picoammeter 6. The detection data is displayed in real time through the data acquisition circuit board 5.

[0068] A reference solution is placed in the reference chamber 1. The reference solution is a 0.01M salt solution; the salt solution is a NaCl solution with pH=7.

[0069] The detection chamber 3 is filled with the solution to be tested (salt solutions with the same concentration but different pH).

[0070] The ion exchange membrane 2 is constructed using a functionalized nanochannel 21 array, and the membrane thickness is 10 micrometers.

[0071] The functionalized nanochannel 21 has a diameter of 20 nanometers; the specific construction method is as follows ( Figure 3 ):

[0072] (1) A porous anodic aluminum oxide film (solid nanochannel) was constructed using aluminum as the material through a two-step oxidation method, wherein the density and diameter of the solid nanochannel were controlled by the oxidation voltage and the composition of the solution.

[0073] (2) Lysine (polyelectrolyte brush layer 212) is grafted onto the inner surface (inner wall of nanochannel wall 211) of solid nanochannel by indirect modification to change the surface properties of nanochannel.

[0074] The thickness of the lysine is d. m =5 nanometers;

[0075] The polyelectrolyte brush layer 212 undergoes protonation and deprotonation reactions, as shown below:

[0076]

[0077]

[0078] A volume charge density related to hydrogen ions will be generated within the polyelectrolyte brush layer 212, and the specific calculation formula is as follows:

[0079]

[0080] Therefore, the surface properties of solid nanochannels can be adjusted by changing the pH of the solution;

[0081] The data acquisition circuit board 5 includes a microprocessor, a lithium battery, and an OLED screen. The connection between the microprocessor, lithium battery, and OLED screen is such that the lithium battery powers the microprocessor and the OLED screen, the ion current collected by the electrode is transmitted to the microprocessor, and the pH value of the solution to be tested is displayed on the OLED screen.

[0082] The correlation between pH and ionic current for different salt solutions (test solutions) was obtained using the Pi-Ammeter 6, as shown in the figure. Figure 4 As shown: when pH is 3, the ion current is 4 pA; when pH is 5, the ion current is 19.75 pA; and when pH is 8, the ion current is 31.52 pA. That is, the magnitude of the ion current changes with the pH of the solution being tested. The relationship between the pH of the salt solution and the ion current is recorded by a program and processed by a microprocessor.

[0083] The microprocessor is based on an STM32-based data acquisition system, which converts the acquired ion current signal into a pH value and displays it directly on an OLED screen.

[0084] It should be noted that the polyelectrolyte brush layer in this embodiment uses lysine as the material. In addition, other pH-sensitive polyelectrolyte materials can also be selected to construct pH-responsive functionalized nanochannels.

[0085] It should be noted that the reference solution in this embodiment is a NaCl solution with a pH of 7 and a concentration of 0.01M. In addition, other salt solutions or deionized water can also be selected as the reference solution.

[0086] Example 2

[0087] This embodiment provides a method for detecting the pH of a salt solution based on salinity gradient conversion, using the salt solution pH detection device based on salinity gradient conversion described in Embodiment 1. (See also...) Figures 1-3 , Figure 1 This is a schematic flowchart of a salt solution pH detection method based on salinity gradient conversion provided in an embodiment of the present invention. In the diagram, the positive and negative signs of the currents indicate the direction of ion current flow, and the numerical values ​​indicate the magnitude of the ion current. Figure 1 As shown, the method for detecting the pH of a salt solution using salinity gradient conversion includes the following steps:

[0088] S1. Preparation of ion exchange membranes;

[0089] S2. The reference chamber and the detection chamber are connected by an ion exchange membrane. A 0.01M salt solution is placed in the reference chamber as a reference solution. The test solutions are placed in the detection chamber respectively. The relationship between the pH of the test solution and the ion current is obtained by the picoammeter.

[0090] S3. The corresponding relationship is recorded by the program, analyzed by the data acquisition circuit board, and converted into a specific value of the salt solution pH, which is then displayed on the OLED screen in real time.

[0091] The ion exchange membrane 2 is constructed using an array of functionalized nanochannels 21, with a membrane thickness of 10 micrometers; the functionalized nanochannels 21 have a diameter of 20 nanometers; the specific construction method is as follows ( Figure 3 ):

[0092] (1) A porous anodic aluminum oxide film (solid nanochannel) is constructed on aluminum foil by a two-step oxidation method, wherein the density and diameter of the solid nanochannel are controlled by the oxidation voltage and the composition of the solution;

[0093] (2) Lysine (polyelectrolyte brush layer 212) is grafted onto the inner surface (inner wall of nanochannel wall 211) of solid nanochannel by indirect modification to change the surface properties of nanochannel.

[0094] The thickness of the lysine is d. m =5 nanometers;

[0095] Step S3 specifically involves placing the salt solution to be tested into the detection chamber, obtaining the real-time ion current through salt difference conversion, analyzing it through the data acquisition circuit board, and converting it into a specific value of the salt solution pH, which is then displayed in real time on the OLED screen.

[0096] Detection applications:

[0097] Taking KCl solution as an example, KCl solutions with pH values ​​of 6, 7 and 8 were tested respectively, and the detected ion currents were 29.59 pA, 31.32 pA and 31.51 pA respectively. The pH value of the tested solution can be directly obtained based on the difference in ion current.

[0098] Comparative Example 1

[0099] This comparative example provides a salt solution pH detection device based on salinity gradient conversion, which differs from the present invention. The device includes a reference chamber, an ion exchange membrane, a detection chamber, electrodes, a data acquisition circuit board, and a picoammeter.

[0100] The reference chamber and the detection chamber are connected by an ion exchange membrane. An electrode is inserted into each of the detection chamber and the reference chamber. The two electrodes are connected in sequence by a data acquisition circuit board and a picoammeter. The detection data is displayed in real time through the data acquisition circuit board.

[0101] A reference solution is placed in the reference chamber. The reference solution is a 0.01M salt solution; the salt solution is a NaCl solution with pH=7.

[0102] The detection chamber is filled with the solution to be tested (salt solutions with the same concentration but different pH).

[0103] The ion exchange membrane is constructed using a solid-state nanochannel array with a thickness of 10 micrometers; the solid-state nanochannels have a diameter of 20 nanometers; the construction method is as follows: using silicon dioxide as a substrate, it is constructed by track etching.

[0104] The solid-state nanochannels will undergo the following reaction:

[0105]

[0106]

[0107] Therefore, a surface charge density related to hydrogen ions will be generated, and the specific calculation formula is as follows:

[0108]

[0109] Therefore, the surface charge density of nanochannels can be adjusted by changing the pH of the salt solution.

[0110] The data acquisition circuit board includes a microprocessor, a lithium battery, and an OLED screen. The connection between the microprocessor, lithium battery, and OLED screen is such that the lithium battery powers the microprocessor and the OLED screen, the ion current collected by the electrode is transmitted to the microprocessor, and the pH value of the solution to be tested is displayed on the OLED screen.

[0111] The relationship between pH and ionic current for different salt solutions (test solutions) was obtained using the picoammeter, such as... Figure 5 As shown; the relationship between the pH of the salt solution and the ion current is recorded by a program and processed by a microprocessor;

[0112] The microprocessor is based on an STM32-based data acquisition system, which converts the acquired ion current signal into a pH value and displays it directly on an OLED screen.

[0113] The test results show that the ion current generated by the silicon-based nanochannel at the same pH is significantly smaller than that of the present invention. Since the detected ion current is in the picoampere range, the detection results of the present invention are more accurate. In addition, the ion exchange membrane mainly controls the ion selectivity in the channel by the surface charge of the nanochannel. Therefore, when the diameter of the nanochannel is too large, the ion selectivity of the nanochannel will decrease, which will lead to a decrease or even disappearance of the detection effect.

[0114] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules, devices, or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0115] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0116] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A salt solution pH detection device based on salinity gradient conversion, characterized in that: Includes a reference chamber, ion exchange membrane, detection chamber, electrodes, data acquisition circuit board, and picoammeter; The reference chamber and the detection chamber are connected by an ion exchange membrane. An electrode is inserted into each of the detection chamber and the reference chamber. The two electrodes are connected in sequence by a data acquisition circuit board and a picoammeter. The detection data is displayed in real time through the data acquisition circuit board. A reference solution is placed in the reference cavity, and the test solution is placed in the detection cavity. The ion exchange membrane is constructed using a functionalized nanochannel array with pH response. The functionalized nanochannels are constructed by building solid nanochannels on anodized aluminum oxide film as a substrate, and then grafting a polyelectrolyte brush layer onto the inner surface of the solid nanochannels. The solid nanochannels are constructed using a two-step oxidation method, with aluminum as the selected material. The polyelectrolyte brush layer is made of lysine. The data acquisition circuit board includes a microprocessor, a lithium battery, and an OLED screen, with the lithium battery powering the microprocessor and the OLED screen. The electrode transmits the collected ion current to the microprocessor. The picoammeter obtains the correspondence between the pH of the test solution and the ion current. The correspondence is recorded by a program and processed by the microprocessor. The collected ion current signal is converted into a pH value and directly displayed on the OLED screen.

2. The salt solution pH detection device based on salinity gradient conversion according to claim 1, characterized in that: The thickness of the polyelectrolyte brush layer is 4-6 nanometers.

3. The salt solution pH detection device based on salinity gradient conversion according to any one of claims 1-2, characterized in that: The diameter of the nanochannels is 18-22 nanometers.

4. The salt solution pH detection device based on salinity gradient conversion according to claim 3, characterized in that: The thickness of the ion exchange membrane is 9.5~10.5 micrometers.

5. The salt solution pH detection device based on salinity gradient conversion according to claim 4, characterized in that: The microprocessor is an STM32 data acquisition system.

6. A method for detecting pH in salt solutions based on salinity gradient conversion, characterized in that: The specific steps of using the salt solution pH detection device based on salinity gradient conversion as described in any one of claims 1-5 are as follows: S1. Preparation of ion exchange membranes; S2. The reference chamber and the detection chamber are connected by an ion exchange membrane. A 0.01M salt solution is placed in the reference chamber as a reference solution. The test solutions are placed in the detection chamber respectively. The relationship between the pH of the test solution and the ion current is obtained by the picoammeter. S3. The corresponding relationship is recorded by the program, analyzed by the data acquisition circuit board, and converted into a specific value of the salt solution pH, which is then displayed on the OLED screen in real time.

7. The method for detecting pH of salt solutions based on salinity gradient conversion according to claim 6, characterized in that, The functionalized nanochannels were prepared by the following method: S101. Using aluminum as the material, a porous anodic aluminum oxide film is obtained through a two-step oxidation method, which yields a solid-state nanochannel. S102. Graft the polyelectrolyte brush layer onto the inner surface of the solid nanochannel to construct a functionalized nanochannel.

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