JPS63153047A - Oxygen electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an oxygen single electrode that enables measurement over a long period of time without renewing the electrolyte.

[Prior Art] Conventionally, electrodes based on constant voltage electrolysis (polarography) have been used to measure changes in oxygen concentration in gases and solutions. This is generally called the oxygen electrode method. In this method, 02 is electrolyzed on the surface of the measuring electrode by applying a constant voltage between both the reference electrode (reference electrode, control electrode, standard electrode) and the measuring electrode, and the 02 is determined by the strength of the electrolytic current. This method measures the concentration of Practical oxygen electrodes use silver for the reference electrode, noble metals such as platinum, gold, silver, etc. for the measurement electrode, and a chloride solution for the electrolyte. Electrolysis is carried out by keeping the potential of the measuring electrode at about -0.6 V with respect to the reference electrode. Therefore, when a voltage of approximately 0°6 V is applied between both electrodes, the reference electrode becomes an anode and the measurement electrode becomes a cathode, and the following electrode reaction proceeds.

Cathode (measuring electrode): 02 + 4H Kai + 48-111 → 2H
20 (acidic solution) 02+2H20+4e-1 → 40H- (neutral and alkaline solution) Anode (reference electrode): 4Ag+4C1 ->4 A g C1+ 4 e (wide pH range) The above anode (reference type S) is Ag/ Since the AgC1 system is formed and the potential is fixed at a constant potential, the cathode is also kept at a constant potential suitable for the reduction of 02, and the above-mentioned polarity response occurs. Therefore, electrons 〇 disappear at the cathode, electrons e are generated at the anode, and a current flows between the two electrodes in proportion to the number of 02 molecules that reach the cathode. Since the number of 02 molecules reaching the cathode is proportional to the 02 concentration in the measurement sample, the 02 concentration can be determined by measuring this current.

Oxygen electrodes can be classified into yin-yang separated type and yin-yang combined type based on how the electrodes are arranged. In the former method, both electrodes are directly immersed in the sample to be measured, and an electrolytic reaction occurs within the sample. IIt people are both! The four electrodes and electrolyte are wrapped in a thin oxygen-permeable plastic film.

This was immersed in the measurement sample and passed through the thin film. 02 is subjected to an electrolytic reaction in an electrolytic solution within a thin film.

Until about 10 years ago, composite oxygen f/l electrodes were exclusively used in the form of long, slender rods with a length several times the diameter. and mint, patent application 1976-76804: Hagiwara,
Patent application 1977-158119; Hagiwara, patent application 1977-10
1235) and oxygen reaction vessels (e.g., Hagiwara, Tokugan Sho 6l)
-146688), flat types with a length shorter than the diameter have also come to be used. Table 1 shows the classification of oxygen electrodes.

(T: extra 6) Table 1 height 7mm) The present invention is a composite FII cumulative electrode.

There are two types of composite oxygen electrodes: one in which the electrode membrane itself is inserted into the electrode part and fixed (hereinafter referred to as membrane fixed type);
A method in which a 11-pole membrane is fixed in advance to a membrane holder and then inserted into the electrode part is called a membrane holder type, for example.
Hagiwara, patent application 1972-158119, patent application 1972-101
235).

Figure 5 shows the conventional membrane-fixed flat oxygen'! A cross-sectional view of four poles is shown. A cathode (measuring electrode, noble metal) 1- is provided at the center of a cylindrical glass 3 that is a cathode insulator, and a cylindrical anode (reference electrode, silver )2 are provided. These are fixed by a plastic electrode support 8. The oxygen-permeable electrode membrane (plastic film) 4 covers the cathode reaction surface 30 and is oxygen-permeable.
It is fixed to the electrode support 8 by a ring 24. A thin layer 5 of electrolyte is deposited on the cathode reaction surface 30 by an electrode film 4.
is held, and ff1. 02 passing through the electrode membrane 4 causes the aforementioned electrolytic reaction in the thin M5 of this electrolytic solution.

In Fig. 5, 9 is an electrode membrane covering plate (protection plate), 21 is a screw for fixing the plate and is made of metal or plastic, 23 is an electrode membrane support (plastic), 16 is
is the electrode lead wire.

[Problems to be solved by the invention] In the case of a composite oxygen electrode, if the composition of the electrolyte changes due to an electrolytic reaction, the sensitivity changes and accurate measurements cannot be performed, so it is necessary to renew the electrolyte. In the conventional composite oxygen electrode as described above, only a small amount of electrolyte is retained in the electrolyte membrane 4, so the composition changes quickly and the electrolyte must be frequently renewed. There wasn't.

Renewing the electrolytic solution requires replacing the electrode film 4, which is complicated, and it is difficult to reproduce the same sensitivity.

To solve this problem, if a large amount of electrolyte is stored, when the electrode is used horizontally or vertically, the electrolyte will leak and cause electrical leakage that will fatally interfere with measurement. There was fear. In particular, flat oxygen electrodes are extremely small in vertical size and do not have enough space to prevent leakage of electrolyte. Therefore, leakage of the electrolyte mentioned above is extremely likely to occur, and a large amount of electrolyte is stored. It was impossible to do so. Furthermore, if the electrolyte is completely sealed to prevent this leakage, the thickness of the electrolyte layer on the reaction surface 30 will change due to internal and external temperature changes and external pressure changes, resulting in the problem of unstable electrolytic sensitivity. arise.

That is, with the conventional composite oxygen electrode, there were problems in that the electrode membrane 4 had to be replaced frequently and the electrolyte solution had to be renewed, which was complicated, and continuous measurement over a long period of time could not be performed.

This invention solves the above-mentioned problems and stores a large amount of electrolyte without sealing it, without leaking the electrolyte even if the electrode is tilted or inverted, and can be used for an extremely long period of time. The purpose is to provide a 7ft combined oxygen capacity that enables stable measurements.

[Means for Solving the Problems] The flat oxygen electrode according to the first invention is provided with an electrolyte storage section for storing a large amount of electrolyte at a position connected to the electrolyte on the cathode reaction surface. The liquid storage compartment is communicated with the outside air through a thin tube, and the inside of the electrolyte storage compartment is maintained at atmospheric pressure.

The flat type M elementary electrode according to the second invention provides an electrolyte storage section for storing the electrolyte at a position connected to the electrolyte on the reaction surface, and closes the end of the elastic tube to store the electrolyte. The interior of the compartment is stably maintained at a pressure just below atmospheric pressure.

[Function] The capillary in the first invention places the boundary between the electrolyte and the atmosphere in the center of the capillary, so that even if the temperature or atmospheric pressure changes, the electrolyte will simply move within the capillary and the electrolyte will flow. The pressure inside the electrolyte storage compartment is always maintained equal to atmospheric pressure without leaking.

Since the elastic tube in the second invention is elastic, the pressure in the electrolyte storage section is kept almost constant even if the end on the atmosphere side is closed. At this time, of course, there is no leakage of the electrolyte.Since the inside of the elastic tube is closed at a pressure slightly lower than atmospheric pressure, the electrode membrane is always drawn toward the measurement surface, and the electrolyte layer on the measurement surface The thickness is kept constant.

[Example] Fig. 1 shows a sectional view of a flat oxygen electrode according to an embodiment of the first invention, and Fig. 2 shows a plan sectional view thereof.This electrode stores a sufficient amount of electrolyte, So-called disposable type long-term sustainability that does not require any assembly by the user! It is extreme. A cathode (measuring electrode) 1 made of a noble metal such as platinum is provided at the center of a cylindrical cathode insulator 3 (glass, ceramic, etc.), and an electrode support 8 is arranged around the outer periphery of the cathode insulator 3. An electrolyte storage section 12 is provided inside the electrode support 8, and the tI of the outer peripheral end surface of the electrolyte storage section 12 is
t! on the ILFi membrane fixing surface 20! A monopolar membrane (02 permeable plastic film) 4 is adhered. The end surfaces of the cathode 1 and the cathode insulator 3 are polished into a flat or nearly spherical shape to form a cathode reaction surface 30 that slightly protrudes from the end surface of the electrolyte storage section 12. The electrolytic solution 7 is stored in a compartment surrounded by the above-mentioned electrolytic solution storage compartment 12 and the electrode [4, and on the cathode reaction surface 30, since the electrode membrane 4 lightly presses this reaction surface, the electrolytic solution 7 exists as the thin layer 5. This thin layer 5 of electrolyte is naturally the electrolyte storage section 1.
It is connected to the electrolyte in 2. In addition, as the electrolyte, K
A CI aqueous solution, a neutral or weakly basic slow r# solution containing CI-, or a mixture thereof with an evaporation inhibitor such as ethylene glycol or glycerin is used. Pancreatic juice storage compartment 1
2 is provided with a positive electrode ff1 (reference electrode) 2 made of silver or the like in contact with the electrolytic solution 7. The fl electrode support is provided with an electrolyte injection pipe 84 leading to the electrolyte storage section, and the electrolyte injection port 84 has a drainage thin tube 83 (for example, an inner diameter of 0.5
The electrolytic solution 7 in which the silicon tube (m111) is fitted is filled into the electrolytic solution storage section 12 by a vacuum introduction method or the like using this thin tube. $111 The length of the tube 83 is such that when the boundary between the electrolyte and the atmosphere is near the center of the thin tube, the electrolyte will not leak out even if there are changes in atmospheric pressure or temperature, and the air will not leak out. The length should be such that it does not enter the electrolyte storage section 12, but usually about 20111 m is sufficient. By providing this thin tube 83, the pressure within the electrolyte storage section 12 is maintained at the same level as the outside pressure.

In addition, since the inner diameter of the capillary tube 83 is extremely thin and long, there is virtually no evaporation of the electrolyte solution.In this way, the electrolyte solution storage section 12 is always kept at the same pressure as the outside pressure, so it is not affected by temperature changes or changes in the outside pressure. Even if there is a problem, the pressing force of the electrode membrane 4 against the cathode measurement surface is kept constant only by the stretching force of the electrode membrane 4, and the thickness of the electrolyte layer 5 is always kept constant. Since the thickness of the electrolytic solution layer 5 controls the amount of O2 molecules reaching the cathode surface, it is extremely important to maintain a stable thickness of this layer in order to obtain stable sensitivity.

The electrode support 8 holds the above-mentioned various members and forms the electrolyte storage section 12, and is usually made only of plastic with good electrical insulation, but when the electrode is provided with a temperature control mechanism, , a plastic part 8P (center part) and a metal part 8K (periphery part), and a heater and a temperature sensor are installed in the metal part 8. The upper and side surfaces of the electrode support are covered with an electrode cap (plastic) 10, and the electrode cap 10 has a handle portion 10a for holding anode/cathode leads 1116 and other various lead wires (described later). . Electrode support 8, various lead wires and electrode cap 10
The space between them is bonded or filled with a filler adhesive 11 such as epoxy. However, the part where the thin tube 84 is housed is not filled with epoxy or the like, but is filled with air, and the electrode cap 1 is
0 is provided with fine ventilation holes 81 for communicating this air phase with the atmosphere.

When measuring oxygen, the electrolyte composition of the electrolyte layer gradually changes on the end surface of the cathode 1, but the electrolyte storage section 12, which stores a large amount of electrolyte, is continuous with the electrolyte layer 5. Therefore, electrolyte components are constantly exchanged, and changes in electrode sensitivity do not occur except at the very beginning of measurement.
Note that the electrolyte composition also changes near the anode 2;
Since the anode 2 is in direct contact with a large amount of electrolyte, the sensitivity is not affected.

In this embodiment, a part 8K of the electrode support 8 is made of a metal with good thermal conductivity, and a heater 19A and a temperature measuring element 1 are provided inside the electrode support 8.
It is equipped with 9B. These constitute constant temperature heating means, and keep the metal part 8 and the metal electrode membrane support 9 at a predetermined temperature. Therefore, for example, it can be applied to the skin and used as a transcutaneous measurement electrode that measures the oxygen concentration of blood while heating the skin.

In the above embodiment, the electrolyte layer on the reaction surface 30 is maintained at a predetermined thickness by forming the cathode reaction surface 30 in a finely roughened state. Stable sensitivity can also be obtained by providing a transparent thin film and containing an electrolyte therein.

FIG. 3 shows a sectional view of a flat oxygen electrode according to another embodiment. In this embodiment, a thin tube 83 contains a layer 50 of an lIt vaporizable liquid that is immiscible with water, such as liquid paraffin. This evaporative liquid layer 50 completely prevents evaporation of the electrolyte, and moreover, this liquid layer 50 moves freely in the thin tube 83 in response to changes in pressure, increasing the pressure in the electrolyte storage section 12. It has the effect of keeping air pressure equal.

FIG. 4 shows a cross-sectional view of a flat oxygen electrode according to an embodiment of the second invention. In this case, a thin elastic tube 85 made of an elastic material (silicone rubber, rubber, etc.) is used for electrolysis. It is connected to a liquid injection port 84, and the electrolytic solution is filled up to the vicinity of this injection port, and most of the end side of the tube 85 is filled with air, and after this air portion is slightly depressurized, the end 85E of the tube 85 is closed. In this way, there is no evaporation of the electrolyte, so the elastic tube 85 does not need to be a thin tube as in the case of the first invention. When the pressure inside the elastic tube 85 is reduced, it is natural that the electrolyte storage section 12 will also be in a reduced pressure state to the same extent. For this reason, the degree of depressurization of the zero elastic tube 85, by which the electrode film 4 is lightly pressed against the cathode measurement surface 30, needs to be adjusted depending on the operating temperature range. It is necessary to keep the pressure inside the storage compartment 12 to a level that does not exceed the atmospheric pressure outside the pole and to prevent the electrode membrane from separating from the cathode reaction surface. For example, use in the range of 20°C to 50°C. In the case of electrodes, it is preferable to maintain the electrode temperature at 20° C. and then close the elastic tube 85 while reducing the pressure to about 0.1 atm, which is slightly more than 30/323=0.093 atm than atmospheric pressure.

Alternatively, as an expedient method, maintain the electrode temperature at about 53°C, then pull out the terminal end 85E of the elastic tube 85 from the ventilation hole 81 of the single-pole cap while maintaining normal pressure, and then correct the part near the terminal. while terminal 85. Just glue the inside of the tube and then store it in the cap.If you adjust the pressure inside the tube 85 as described above, even if there are changes in temperature or outside pressure, most of the pressure changes will be caused by the elastic tube. Since the electrolyte layer 5 is absorbed by the elasticity of the electrode film 4 and the cathode measurement surface 30, the thickness of the electrolyte layer 5 between the electrode film 4 and the cathode measurement surface 30 is kept almost constant, and measurement sensitivity is stabilized.

In addition, when measuring the oxygen concentration of blood by pasting electrodes on the skin, the second invention also provides constant temperature heating means as in the first invention to improve blood circulation and facilitate measurement. be able to.

In addition to the oxygen electrode described above, there is a galvanic cell type oxygen measuring electrode that is very similar to the oxygen electrode. In this case, lead is used as the oxygen electrode corresponding to the reference electrode (silver), an alkaline solution is used instead of the chloride solution as the electrolyte, and silver, which has a lower overvoltage than 02, is used as the measurement electrode.

The potential of this lead electrode (lead/lead hydroxide system) is much lower than that of the silver/silver chloride thread, so unlike the oxygen electrode, the measurement electrode (
The reduction reaction of 02 occurs without applying a negative voltage to silver). Therefore, in this case, a galvanic cell is constructed in which the 02 measuring electrode is the anode and the lead electrode is the cathode. Therefore, although they appear to be significantly different from oxygen electrodes that perform electrolysis, both are composed of two types of electrodes (however, the positive and negative names are reversed) and an electrolyte, and a voltage is applied between the two electrodes. The only difference is whether or not it is added, so the relationship between structure and function is strikingly similar.

Therefore, the invention of the present application relating to the structure of the oxygen electrode is also applicable to a galvanic cell type oxygen measuring electrode. That is, in this specification, the term "acid X electrode" includes the above-mentioned galvanic cell type single element measurement electrode.

[Effect of the invention] The oxygen electrode according to the first invention is provided with an electrolyte storage section,
This interior is communicated with the outside through a thin tube. Since a thin tube is used, leakage of the electrolyte to the outside and evaporation of the electrolyte are prevented, and the electrolyte storage compartment is maintained at the same atmospheric pressure as the outside pressure. Therefore, even if there is a rise in temperature or a change in external pressure, the thickness of the electrolyte layer on the measurement surface does not change and is kept constant, resulting in stable measurement sensitivity over a long period of time.

The oxygen electrode according to the second invention is provided with an electrolyte storage section that is sealed from the outside air, an elastic tube is connected to this, and the inside of the electrolyte storage section and the elastic tube is kept at a pressure slightly below atmospheric pressure. It is kept low and sealed from the outside air. Therefore, the degree of this pressure reduction is kept almost constant due to the elasticity of the elastic tube, even when the temperature rises or the external pressure changes, and the thickness of the electrolyte layer on the cathode measurement surface remains essentially constant. measurement sensitivity is stable. In the case of the second invention, since the electrolyte storage compartment is sealed from the outside air, leakage of the electrolyte to the outside and evaporation of the electrolyte are completely prevented, allowing long-time measurements.

That is, according to the first and second inventions, it is possible to provide an oxygen electrode that can perform stable measurements over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a flat oxygen electrode according to an embodiment of the first invention, FIG. 2 is a plan sectional view of the flat oxygen TL electrode of FIG. 1, and FIG. FIG. 4 is a side sectional view of a flat oxygen electrode according to an embodiment of the second invention, FIG. 5 is a side sectional view of a conventional flat oxygen electrode. It is a diagram. 1 is a cathode, 2 is an anode, 3 is a cathode insulator, 4 is an electrode film, 5
is an electrolytic solution layer, 8 is an electrode support, 12 is an electrolytic solution storage section,
83 is a thin tube, and 85 is an elastic tube. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (10)

[Claims] (1) A cathode whose end surface is in contact with the electrolyte, an anode which is provided in contact with the electrolyte and is electrically connected to the cathode via the electrolyte, an electrode support holding the anode and cathode, and an end surface of one end of the cathode. A cathode reaction surface is formed, an oxygen-permeable electrode film is provided covering the reaction surface to hold a thin layer of electrolyte on the cathode reaction surface, and an electrolyte is placed on the cathode reaction surface at a position connected to the electrolyte layer. An oxygen electrode characterized by comprising: an electrolyte storage compartment which stores an electrolyte and whose pressure is kept equal to atmospheric pressure by contacting the atmosphere through a thin and long tube. (2) The cathode reaction surface is slightly protruded from the electrode membrane fixing surface, and the electrode membrane is expanded by the protrusion of the cathode reaction surface. oxygen electrode. (3) The oxygen electrode according to claim 2, wherein the cathode reaction surface is formed into a finely roughened surface. (4) Claim 2, characterized in that it has a porous thin film containing an electrolyte on the upper surface of the cathode reaction surface.
Oxygen electrode as described in section. (5) Claims 1, 2, 3, or 4, characterized in that a small amount of a liquid that is difficult to evaporate is sealed inside the thin tube connected to the electrolyte storage section. The oxygen electrode described in section. (6) A part of the electrode support is made of a thermally conductive metal, and this metal part is maintained at a predetermined temperature by constant temperature heating means. The oxygen electrode according to item 2, 3, 4, or 5. (7) A cathode in contact with the electrolyte, an anode provided in contact with the electrolyte and electrically connected to the cathode via the electrolyte, an electrode support holding the anode and cathode, and an end face of one end of the cathode. The cathode reaction surface has a thin layer of electrolyte on the cathode reaction surface, an oxygen-permeable electrode film is provided covering the reaction surface to hold the electrolyte in a thin layer, and the electrolyte is placed on the cathode reaction surface at a position connected to the electrolyte layer. an electrolyte storage compartment having one end connected to the electrolyte storage compartment and the other end closed;
An oxygen electrode comprising: an elastic tube that adjusts the inside of the electrode and the inside of the electrolyte storage section to be slightly lower than the outside air, and stably maintains this reduced pressure state by its elasticity. (8) The oxygen electrode according to claim 7, wherein the cathode reaction surface is formed into a finely roughened surface in order to stably hold the electrolyte. (9) The oxygen electrode according to claim 7, wherein the cathode reaction surface has a porous thin film containing an electrolyte on its upper surface. (10) A portion of the electrode support is made of a thermally conductive metal and is maintained at a predetermined temperature by constant temperature heating means. The oxygen electrode according to item 9.