JPH046455A - Oxygen electrode - Google Patents

Abstract

PURPOSE:To make it possible to replace electrolyte without skill and without the replacement of a gas transmitting film by forming an electrode of a cathode or a plate body wherein an acting electrode has holes, fixing a gas transmitting film on the outer surface of the plate body, and forming a unitary body. CONSTITUTION:A cathode 1 comprises a plate body wherein many holes 6 are formed. A gas transmitting film 3 is bonded, thermally fused and bonded or applied on the surface of the cathode 1. Thus, the cathode 1 and the transmitting film 3 are formed as a unitary body. Therefore, it is not necessary to replace the transmitting film 3 when an oxygen electrode is disassembled and assembled for replacing the electrolyte. Since the relative position relationship between the cathode 1 and the transmitting film 3 is not changed in this way, the characteristics of the oxygen electrode are not changed before and after the replacement of the electrolyte. Since the transmitting film 3 and the cathode 1 have the unitary structure, skill is not especially required in disassembling and assembling. Since the transmitting film 3 is fixed to the cathode 1 and reinforced, the breakdown of the transmitting film 3 itself is avoided, and the semipermanent use can be achieved.

Description

[Detailed description of the invention] Required by Cm] Improvement of the oxygen electrode, in particular, it does not require skill in changing the electrolyte, its characteristics do not change before and after replacing the electrolyte, and there is no °=. Regarding the improvement of the oxygen electrode to prevent the gas-permeable membrane from being damaged, it is possible to replace the electrolyte without replacing the gas-permeable membrane, and therefore, it requires no skill (7).
The purpose is to provide an oxygen electrode in which the characteristics of the oxygen electrode do not change before and after electrolyte exchange, and the gas i1 membrane is not damaged. In an oxygen electrode consisting of a cylindrical container in which a positive and a negative electrode are placed, the negative electrode is made of a plate having an opening,
The above-mentioned gas permeable membrane is fixed to the outer surface of this plate-like body, or an electrolytic solution is put therein, a gas permeable membrane is stretched over one end, and a working electrode, a reference electrode, and a counter electrode are connected to each other. In the oxygen electrode formed of a cylindrical container filled with oxygen, the working electrode is composed of a plate-like body having an opening, and the gas-permeable membrane is fixed to the outer surface of the plate-like body. .

C. Industrial Application Field] The present invention aims to improve oxygen electrodes, in particular, does not require skill in replacing the electrolyte, does not change its characteristics before and after replacing the electrolyte, and has a gas-permeable membrane. This invention relates to improvements in oxygen electrodes that prevent them from being damaged.

[Conventional technology]

Oxygen electrodes are used in various fields to measure dissolved oxygen concentration. For example, it is used to measure biochemical oxygen demand (BOD) in water in order to preserve water quality, and in the fermentation industry, it is used to measure dissolved acidity in fermenters in order to promote efficient fermentation of alcohol, etc. It is used to measure the concentration.Furthermore, it is used in combination with enzymes to form an enzyme electrode and used to measure the concentration of oats, vitamins, etc.0 For example, glucose is oxidized to dissolved oxygen using an enzyme called glucose oxidase. It reacts and is oxidized to gluconolactone, which reduces the amount of dissolved oxygen that diffuses into the oxygen electrode, which can be used to measure the glucose concentration.

In addition to measuring dissolved oxygen, it can also be used to manage oxygen concentration in the air, during suction from an oxygen cylinder, or during gas anesthesia.

As described above, oxygen electrodes can be widely used in various fields such as environmental measurement, fermentation industry, clinical medicine, and occupational safety, and have extremely high utility value.

By the way, there are two types of oxygen electrodes: a two-electrode type and a three-electrode type. 2 [As much as possible, the positive electrode (hereinafter referred to as anode)
It consists of two electrodes: a negative electrode (hereinafter referred to as cathode), and there are Clark type and galvanic type. The Clark type is a voltage application type in which the cathode is made of gold or platinum and the anode is made of silver, and the oxygen concentration is measured by applying a voltage from the outside and measuring the current flowing between the two electrodes. The cathode is made of gold or platinum, and the anode is made of lead, respectively, and is a self-powering type that measures the oxygen concentration by measuring the current flowing between the two electrodes without applying an external voltage. The 3-electrode system has a working electrode, a counter electrode,
The reference electrode consists of 3if&, the working electrode and the counter electrode are made of gold or platinum, the reference electrode is made of silver,
The oxygen concentration is measured by applying a constant voltage between the reference electrode and the working electrode and measuring the current flowing between the counter electrode and the working electrode.

In Fig. 3, a cross-sectional view of an oxygen electrode according to the prior art is shown, taking a two-electrode method as an example, and in Fig. 0, 1 is a cathode;
2 is an anode, 3 is a gas permeable membrane made of fluororesin, silicone resin, etc., 4 is an electrolytic solution, and 5 is a cylindrical container made of glass, plastic, stainless steel, etc. The gap between the cathode 1 and the gas permeable membrane 3 is extremely small, and the electrolytic solution is interposed therein in the form of a thin film.

In the case of the Clark type oxygen electrode, as described above, the cathode 1 is made of gold or platinum, the anode 2 is made of silver, and the electrolyte 4 is made of potassium chloride water. A solution containing halogen ions such as 8 solution is used. Oxygen that has permeated through the gas permeable membrane 3 is distributed between the anode 2 and the cathode 1 by 0.5~
When a voltage of 2V is applied, reduction occurs on the cathode 1 by an electrochemical reaction shown in the following equation, and a current proportional to the acidity concentration flows.

Reaction at the cathode: Ox +2HzO+4 e --40H Reaction at the anode: A g + C1 --- A g CIL + e ~,
In the case of a galvanic oxygen electrode, the cathode 1 is made of gold or platinum, the anode 2 is made of lead, and the electrolyte 4 is an alkaline solution such as an aqueous sodium hydroxide solution. In this case, since a lead battery is formed between the cathode 1 and the anode 2, there is no need to apply an external voltage, and a current proportional to the oxygen concentration flows due to the electrochemical reaction shown in the following equation.

Reaction at the cathode: Ot + 2 H, O+ 4 e-440H Reaction at the anode: P b + 20H-□P b (OH) z + 2 e3
In the case of the electric scraping method, a working electrode made of gold or platinum is arranged opposite to the gas permeable membrane 3, and a counter electrode made of gold or platinum and a reference electrode made of silver are arranged in the cylindrical container 5. As the electrolytic solution 4, a solution containing halogen ions, such as an aqueous potassium chloride solution, is used.

When a constant voltage is applied between the reference electrode and the working electrode, a current proportional to the oxygen concentration flows between the working electrode and the counter electrode.

[Problem to be solved by the invention]

In the oxygen electrode, the anode 2 and electrolyte 4 are gradually consumed during use. If the anode 2 is of sufficient size and is placed in the cylindrical container 5 in advance, there is little need to replace it, but the electrolyte 4 not only gets consumed with use, but also leaks and dries out. Because of this, it needs to be replaced frequently.

Many oxygen electrodes have a structure in which the gas permeation W 13 must also be replaced when the electrolyte 4 is replaced. The characteristics of the oxygen electrode, such as response speed and sensitivity, change greatly in response to the relative positional relationship between the gas permeation 11!3 and the cathode 1, which face each other with a small gap between them. When the relative positional relationship between the gas permeable membrane 3 and the cathode 1 shifts, a problem arises in that the characteristics of the oxygen electrode change. To prevent the characteristics from changing,
Requires a high level of skill for disassembly and assembly. In addition, the gas permeable membrane 3 is generally in the form of a very thin film and is easily damaged, so the current situation is that the oxygen electrode must be frequently disassembled and replaced. As described above, conventional oxygen electrodes have a major drawback in that maintenance management is extremely troublesome.

The purpose of the present invention is to eliminate this drawback, and it is possible to replace the electrolyte without requiring skill or replacing the gas permeable membrane, and therefore, before and after replacing the electrolyte. An object of the present invention is to provide an oxygen electrode whose characteristics do not change and whose gas permeable membrane is not damaged.

[Means to solve the problem]

The above object can be achieved by any of the following means. The first means is a cylindrical container (5) in which an electrolytic solution (4) is placed, a gas permeable membrane (3) is stretched over one end, and positive and negative electrodes (1) and (2) are charged. ), the negative electrode (1) is a plate-shaped body having an opening (6), and the gas-permeable membrane (3) is fixed to the outer surface of this plate-shaped body. be. In the second method, an electrolytic solution (4) is placed, a gas permeable membrane (3) is stretched on one end, and a working electrode (11), a reference electrode (step 2), and a counter electrode (13) are placed. In the oxygen electrode made of a cylindrical container (5), the working electrode (11) is made of a plate-like body having an opening (6), and the gas permeation l11 is formed on the outer surface of this plate-like body.
(3) is an oxygen electrode to which is fixedly attached.

[Function] In the oxygen electrode according to the present invention, the gas permeable film 3 is bonded, thermally fused, or coated on the surface of the cathode 1, which is a plate-shaped body in which a large number of openings 6 are formed, so that the cathode 1 and Since the gas permeable membrane 3 is formed integrally with the gas permeable membrane 3, there is no need to replace the gas permeable membrane 3 when disassembling and reassembling the oxygen electrode for replacing the electrolyte.
Since the relative positional relationship between the electrode and the gas permeable membrane 3 does not change, the characteristics of the oxygen electrode do not change before and after replacing the electrolyte, and the gas permeable membrane 3 and the cathode 1 are integrated. Since the gas permeable membrane 3 is fixed to the cathode 1, no special skill is required for disassembly and assembly.
Since it has a reinforced structure, the gas permeable membrane 3 itself is not damaged and can be used semi-permanently.

The sensitivity of the oxygen electrode is proportional to the surface area of the cathode, but in the present invention, the cathode reaction occurs at the edges of the openings 6, so the surface area of the cathode is proportional to the size and number of the openings 6. That is, the larger the diameter of the openings 6 and the larger the number of openings 6, the larger the surface area. Therefore, by adjusting the size and number of openings 6 formed in the cathode 1, the sensitivity of the oxygen electrode can be easily adjusted.

〔Example〕

Hereinafter, an oxygen electrode according to an embodiment of the present invention will be further described with reference to the drawings.

】""sex A two-electrode force type oxygen electrode will be explained.

See FIG. 1 FIG. 1 shows a sectional view of a two-electrode force type oxygen electrode according to the present invention. In the figure, 1 is a cathode, 2 is an anode, 3 is a gas permeable membrane, 4 is an electrolyte,
5 is a cylindrical container, 6 is an opening formed in the cathode 1, 7 is a fixture for fixing the cathode 1 to the cylindrical container 5, 8 is a metal tube for cathode wiring, and 9 is an insulating tube. It is a cylinder.

For the cathode 1, a metal plate with a thickness of 0.1 to 1 mm is used. The most desirable material for the metal plate is platinum or gold, but these are expensive, so stainless steel, iron, copper,
General-purpose metals such as brass can also be used. Ta-shi,
In this case, it is desirable to form a thin film of platinum or gold on the surface of these metals by using a plating method, a gold-plating method, a sputtering method, or the like. An opening 6 having a diameter of 50 nm to 1 mm, preferably 500 nm or less in diameter, is formed in this metal plate. In general, the shape of the aperture is circular, square, or hexagonal, which are advantageous for manufacturing purposes, but if the shape is star-shaped, where the edge is longer than the diameter, the sensitivity per unit area may be reduced. growing. Therefore, the shape of the opening 6 may be selected in response to the required characteristics of the oxygen electrode.

The method for forming the openings 6 is to form a resist layer on a metal plate, pattern it using photolithography, remove it from the area where the openings 6 are to be formed, and use this resist pattern as a mask to form a resist layer on the metal plate. Although etching is a common method, depending on the size and number of the openings 6, it is also possible to form them by directly drilling holes in the metal plate using a drill or the like.

A gas permeable WI3 is formed on the surface of the cathode 1 in which the opening 6 is formed using one of the following methods.

(a) A plastic film such as a fluororesin film is heat-sealed to the surface of the cathode 10.

(b) A plastic film such as a fluororesin film is adhered to the surface of the cathode 1.

(c) Apply a plastic such as fluororesin paint or silicone resin to the surface of the cathode l.

A metal tube 8 for cathode wiring is formed on the inner surface of the cylindrical container 5, and an insulation wi9 is further formed on the inner surface. The cylindrical container 5 is filled with electrolyte 4, and the gas permeates through it! 3
The fixed cathode 1 is placed on the open end of the cylindrical container 5 and fixed by tightening the fixture 7. At the lower end of the cylindrical container 5, a current proportional to the oxygen concentration can be taken out between the cathode wiring metal tube 8 in contact with the cathode 1 and the anode 2.

Incidentally, it is important that the opening 6 of the cathode 1 is filled with the electrolytic solution 4. It will work as an oxygen electrode even when unfilled, but the response time and sensitivity will be poor.

Since the openings 6 are very fine, they are difficult to fill with the electrolyte 4. Therefore, use one of the methods below to fill the electrolyte 4.
It is desirable that the opening 6 be filled with the following.

(a) The cathode 1 with the gas permeable membrane 3 formed thereon is immersed in an electrolytic solution and the pressure is reduced. Since the air in the opening 6 is removed by reducing the pressure, when the pressure is returned to atmospheric pressure, the opening 6 is filled with electrolyte.

(b) Gas permeation! ! The cathode 1 with the formed cathode 3 is immersed in a degassed electrolyte solution and left for a while. The air in the opening 6 gradually dissolves into the electrolytic solution, and the opening 6 is filled with the electrolytic solution.

In the case of the Clark type oxygen electrode, the anode 2 is formed of silver, and the electrolyte 4 is a solution containing halogen, such as an aqueous potassium chloride solution.

A voltage of 0.5 to 2 cm is applied between the anode 2 and the cathode 1, and the current flowing between the two electrodes is measured to measure the oxygen concentration.

In the case of a galvanic type oxygen electrode, the anode 2 is made of lead, and the electrolyte 4 is an alkaline solution such as sodium hydroxide. The oxygen concentration is measured by measuring the current flowing between the anode 2 and the cathode 1 without applying an external voltage.

”” Unspoken A three-electrode blade type oxygen electrode will be explained.

See Figure 2 In Figure 2, 3 is a cross-sectional view of a scraper-type oxygen electrode according to the present invention, 11 is a working electrode made of gold or platinum, and 12 is a reference electrode made of silver. 13 is a counter electrode made of gold or platinum, 0 working electrode 1 and counter electrode 13.
As in the first example, a thin film of platinum or gold may be formed on the surface of a general-purpose metal. 3 is a gas permeable membrane fixed to the working electrode 11, 4 is an electrolytic solution containing halogen ions such as an aqueous potassium chloride solution, 5 is a cylindrical container, and 6 is an opening formed in the working electrode 11. 7 is a fixture for fixing the working electrode 11 to the cylindrical container 5, 8 is a metal tube for wiring the working electrode, and 9 is an insulating tube. The method for forming the working electrode 11 is as follows:
The method for forming the cathode 1 in the first example is the same, and the method for forming the gas permeable membrane 3 is the same as in the first example.

〔Effect of the invention〕

As explained above, in the oxygen electrode according to the present invention, the cathode or the working electrode is constituted by a plate-like body having an opening, and the gas permeable membrane is fixed and integrated on the outer surface of this plate-like body. The electrolyte can be replaced without requiring any skill or without replacing the gas permeable membrane.

Therefore, since the relative positional relationship between the gas permeable membrane and the cathode or working electrode does not change, the characteristics of the oxygen electrode do not change before and after replacement.

Further, since the gas permeable membrane has a reinforced structure by being fixed to the cathode or working electrode, damage is prevented and semi-permanent use is possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a two-electrode blade type oxygen electrode according to an embodiment of the present invention. FIG. 2 is a sectional view of an ati type oxygen electrode according to an embodiment of the present invention. FIG. 3 is a sectional view of a two-electrode blade type oxygen electrode according to the prior art. 12...Reference pole, 13...Counter pole.

Claims (1)

[Claims] [1] An electrolytic solution (4) is placed, and a gas permeable membrane (
3), the negative electrode (1) is a plate-shaped container having an opening (6). An oxygen electrode characterized in that the gas permeable membrane (3) is fixed to the outer surface of the plate-like body. [2] The electrolyte (4) is put in, and a gas permeable membrane (
3) is stretched, and a cylindrical container (5) is charged with a working electrode (11), a reference electrode (12), and a counter electrode (13), the working electrode (11) is open. (6) An oxygen electrode comprising a plate-shaped body having the gas permeable membrane (3) fixed to the outer surface of the plate-shaped body.