Salt-free bridge type pH value PH sensor

Abstract

The invention provides a salt-bridge-free pH value PH sensor, and relates to the technical field of sensors, the salt-bridge-free pH value PH sensor comprises a solid salt bridge shell, the solid salt bridge shell is hollow, an inner core glass tube is fixed in the hollow solid salt bridge shell, the bottom end of the inner core glass tube is provided with a sensitive ball film, and the sensitive ball film is provided with a plurality of sensing balls. An outer electrode is arranged in the solid salt bridge shell, and an inner electrode is arranged in the inner core glass tube. Through the solid salt bridge shell, the shell has ionic conductivity, an electric loop measured by the pH electrode can be conducted under the condition that a potassium chloride gel solution does not make direct contact with a to-be-measured solution, the probability that the salt bridge is polluted and blocked can be reduced through the shell, and the service life of the pH electrode is prolonged; the POM material can be used for a long time within the temperature range of-40 DEG C to 104 DEG C, the conductive performance of the POM can be remarkably improved by adding the conductive material into the POM, and the materials can form a conductive network and promote electron conduction, so that the conductivity of the POM is increased.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, in particular to a salt-free bridge type pH sensor. Background Art

[0002] pH sensors are important tools for measuring the acidity and alkalinity of solutions and are widely used in the fields of chemistry, environmental monitoring, and food industry. The basic working principle is to use the electrode's response to the hydrogen ion concentration in the solution to generate an electrical signal proportional to the pH value.

[0003] In most cases, in a composite pH electrode, the reference potential comes from the Ag / AgCl entering the external reference solution, which exchanges ions with the test solution through a zirconium oxide salt bridge embedded in the glass shell. Normally, the porous salt bridge allows ions to flow from the reference cell to the test solution and vice versa. Since the zirconium oxide salt bridge is prone to clogging, a porous tetrafluoroethylene salt bridge PTFE was later used to solve the disadvantage of easy complexation and clogging during slurry or sewage treatment. However, in this system, the non-pressure-resistant property of PTFE makes the electrode unable to be used normally in many working conditions. All of the above reference systems have their own advantages and disadvantages, but a common problem is that if the pores of the porous structure are too small, the flow rate of the external reference potassium chloride is too low, which will cause a drift in the zero potential. However, if the pore size is too large, the outflowing potassium chloride will cause contamination of the solution to be tested and is prone to clogging, resulting in a significant shortening of the electrode life. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a salt-free bridge pH sensor, which solves the basic problem of salt bridge blockage and the problem that the PTFE salt bridge cannot withstand pressure.

[0006] (II) Technical solution

[0007] To achieve the above purpose, the present invention provides the following technical solutions: a salt-free bridge type pH sensor, comprising a solid salt bridge shell, wherein the solid salt bridge shell adopts a hollow setting, an inner core glass tube is fixed in the hollow of the solid salt bridge shell, a sensitive ball membrane is installed at the bottom end of the inner core glass tube, an outer electrode is arranged inside the solid salt bridge shell, and an inner electrode is arranged inside the inner core glass tube.

[0008] Preferably, the interior of the solid salt bridge shell is filled with a gel solution, and the gel solution is a potassium chloride solution.

[0009] Preferably, the interior of the inner core glass tube is filled with a buffer solution, and the pH value of the buffer solution is 7.0.

[0010] Preferably, the inner electrode and the outer electrode are Ag / AgCl.

[0011] Preferably, a preparation process of a salt-free bridge pH sensor comprises the following steps:

[0012] S1. Mix POM and conductive material in a certain proportion to ensure uniform dispersion;

[0013] S2. Use an injection molding machine to heat the mixed material to a molten state, and then injection mold it into a rod with a width of 13 mm and a length of 10 m;

[0014] S3. The injection molded rod is cut into a length of 128 mm, and a shell with a middle aperture of 7 mm is processed on a CNC machine tool, and two grooves with a width of 1 mm are processed at the bottom to obtain a solid salt bridge shell;

[0015] S4. Install the inner core glass tube into the 7mm middle hole, then blow the sensitive ball membrane into the bottom of the 4.7mm wide glass tube, then insert two O-rings on the top of the sensitive ball membrane and assemble it with the solid salt bridge shell, making sure that the O-rings are correctly inserted into the groove;

[0016] S5. Place the inner electrode into the inner core glass tube, and then add pH 7.0 buffer solution into the inner core glass tube. Temperature compensation installation and sealing can be performed as required;

[0017] S6. Place the outer electrode into the solid salt bridge housing, and inject potassium chloride gel solution into the solid salt bridge housing to ensure stable electrode performance, and finally obtain a salt-bridge-free pH sensor.

[0018] Preferably, the conductive material in S1 is selected from any one of carbon black, polypyrrole, polyaniline, silver powder and copper powder, and the ratio of POM to the conductive material is 8:2.

[0019] (III) Beneficial effects

[0020] The present invention provides a salt-free bridge pH sensor, which has the following beneficial effects:

[0021] 1. The present invention proposes a shell that does not require a salt bridge, namely a solid salt bridge shell. The shell has ionic conductivity and can make the electrical circuit of the pH electrode measurement conductive when the potassium chloride gel solution and the solution to be tested are not in direct contact. The shell can also reduce the probability of pollution blocking the salt bridge and extend the life of the pH electrode. Therefore, the present application solves the basic problem of salt bridge blockage and the problem that the PTFE salt bridge cannot withstand pressure. It is particularly suitable for severe working conditions such as desulfurization and denitrification and is suitable for medium-high pressure and high temperature environments such as fermentation tanks.

[0022] 2. The POM material of the present invention can be used for a long time within a temperature range of -40°C to 104°C, and the addition of conductive materials in POM can significantly improve its conductive properties. These materials can form a conductive network to promote the conduction of electrons, thereby increasing the conductivity of POM. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the present invention.

[0024] Among them, 1. solid salt bridge shell; 2. gel solution; 3. sensitive ball membrane; 4. inner electrode; 5. outer electrode; 6. buffer solution; 7. inner core glass tube. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example:

[0027] like Figure 1 As shown, the embodiment of the present invention provides a salt-free bridge pH sensor, including a solid salt bridge housing 1, the solid salt bridge housing 1 is hollow, an inner core glass tube 7 is fixed in the hollow of the solid salt bridge housing 1, a sensitive ball membrane 3 is installed at the bottom end of the inner core glass tube 7, an outer electrode 5 is arranged inside the solid salt bridge housing 1, and an inner electrode 4 is arranged inside the inner core glass tube 7;

[0028] The interior of the solid salt bridge shell 1 is filled with a gel solution 2, and the gel solution 2 is a potassium chloride solution;

[0029] The interior of the inner core glass tube 7 is filled with a buffer solution 6, and the pH of the buffer solution 6 is 7.0;

[0030] The inner electrode 4 and the outer electrode 5 are Ag / AgCl.

[0031] The present application proposes a shell that does not require a salt bridge, namely a solid salt bridge shell 1. The shell has ionic conductivity and can make the electrical circuit of the pH electrode measurement conductive when the potassium chloride gel solution 2 and the solution to be tested are not in direct contact. The shell can also reduce the probability of pollution blocking the salt bridge and extend the life of the pH electrode. Therefore, the present application solves the basic problem of salt bridge blockage and the problem that the PTFE salt bridge cannot withstand pressure. It is particularly suitable for severe working conditions such as desulfurization and denitrification and is suitable for high pressure and high temperature environments such as fermentation tanks.

[0032] A preparation process of a salt-free bridge pH sensor comprises the following steps:

[0033] S1. Mix POM and conductive material in a certain proportion to ensure uniform dispersion;

[0034] S2. Use an injection molding machine to heat the mixed material to a molten state, and then injection mold it into a rod with a width of 13 mm and a length of 10 m;

[0035] S3. The injection molded rod is cut into a length of 128 mm, and a shell with a middle aperture of 7 mm is processed on a CNC machine tool, and two grooves with a width of 1 mm are processed at the bottom to obtain a solid salt bridge shell 1;

[0036] S4. Install the inner core glass tube 7 into the middle hole of 7 mm, then blow the sensitive ball membrane 3 into the bottom of the glass tube 7 with a width of 4.7 mm, then insert two O-rings on the top of the sensitive ball membrane 3, and assemble it with the solid salt bridge housing 1, making sure that the O-rings are correctly inserted into the groove;

[0037] S5. Place the inner electrode 4 into the inner core glass tube 7, and then add a pH 7.0 buffer solution 6 into the inner core glass tube 7, and perform temperature compensation installation and sealing according to demand;

[0038] S6. Place the outer electrode 5 into the solid salt bridge housing 1, and inject the potassium chloride gel solution 2 into the solid salt bridge housing 1 to ensure the stability of the electrode performance, and finally obtain a salt-bridge-free pH sensor.

[0039] The conductive material in S1 is selected from any one of carbon black, polypyrrole, polyaniline, silver powder and copper powder, and the ratio of POM to the conductive material is 8:2.

[0040] POM material is a high-performance thermoplastic engineering plastic with good physical, mechanical and chemical properties. In addition, POM material also has good electrical and chemical properties. It is resistant to solvents, oils, weak acids, weak alkalis, etc. It has a high heat deformation temperature and can be used for a long time in the temperature range of -40°C to 104°C. Adding conductive materials to POM can significantly improve its conductive properties. These materials can form a conductive network and promote the conduction of electrons, thereby increasing the electrical conductivity of POM.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A salt-free bridge pH sensor, comprising a solid salt bridge housing (1), characterized in that: The solid-state salt bridge shell (1) is hollow, an inner core glass tube (7) is fixed in the hollow of the solid-state salt bridge shell (1), a sensitive ball membrane (3) is installed at the bottom end of the inner core glass tube (7), an outer electrode (5) is arranged inside the solid-state salt bridge shell (1), and an inner electrode (4) is arranged inside the inner core glass tube (7).

2. A salt-free bridge pH sensor according to claim 1, characterized in that: The interior of the solid salt bridge shell (1) is filled with a gel solution (2), and the gel solution (2) is a potassium chloride solution.

3. The salt-free bridge pH sensor according to claim 1, characterized in that: The interior of the inner core glass tube (7) is filled with a buffer solution (6), and the pH of the buffer solution (6) is 7.

0.

4. The salt-free bridge pH sensor according to claim 1, characterized in that: The inner electrode (4) and the outer electrode (5) are Ag / AgCl.

5. A preparation process of a salt-free bridge pH sensor, characterized in that: The following steps are involved: S1. Mix POM and conductive material in a certain proportion to ensure uniform dispersion; S2. Use an injection molding machine to heat the mixed material to a molten state, and then injection mold it into a rod with a width of 13 mm and a length of 10 m; S3. The injection molded rod was cut into a length of 128 mm, and a shell with a middle aperture of 7 mm was processed on a CNC machine tool, and two grooves with a width of 1 mm were processed at the bottom to obtain a solid salt bridge shell (1); S4. Install the inner core glass tube (7) into the middle hole of 7 mm, then blow the sensitive ball membrane (3) into the bottom of the glass tube (7) with a width of 4.7 mm, then insert two O-rings on the top of the sensitive ball membrane (3), and assemble it with the solid salt bridge housing (1), making sure that the O-rings are correctly inserted into the groove; S5. Place the inner electrode (4) into the inner core glass tube (7), and then add a pH 7.0 buffer solution (6) into the inner core glass tube (7). Temperature compensation can be installed and sealed according to needs; S6. Place the outer electrode (5) into the solid salt bridge housing (1), and inject potassium chloride gel solution (2) into the solid salt bridge housing (1) to ensure stable electrode performance, and finally obtain a salt-bridge-free pH sensor.

6. The salt-free bridge pH sensor according to claim 5, characterized in that: The conductive material in S1 is selected from any one of carbon black, polypyrrole, polyaniline, silver powder and copper powder, and the ratio of POM to the conductive material is 8:2.

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