JPH0244537B2

JPH0244537B2 -

Info

Publication number: JPH0244537B2
Application number: JP61300390A
Authority: JP
Inventors: Bunji Hagiwara
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-12-16
Filing date: 1986-12-16
Publication date: 1990-10-04
Also published as: JPS63153047A

Description

[Detailed description of the invention]

［産業上の利用分野］この発明は電解液を更新せずに長時間にわたつ
て測定を可能にした酸素電極に関するものであ
る。［従来の技術］従来より気体中及び溶液中の酸素濃度の変化を
計測するため、定電圧電解法（ポーラログラフイ
ー）による電極が用いられている。これは一般に
酸素電極法と呼ばれている。この方法は、照合電
極（参照電極、対照電極、標準電極）と測定電極
の両電極間に一定の電極を加えて測定電極の面上
でO₂を電解し、その電解電流の強さによつてO₂
の濃度を測定する方法である。実用の酸素電極で
は照合電極に銀を、測定電極に白金、金、銀など
の貴金属を、電解液に塩化物溶液を用いる。照合
電極に対して測定電極の電位を約−0.6Vに保つ
て電解を行わせている。したがつて両電極間に約
0.6Vの電圧をかけると照合電極が陽極に、測定
電極が陰極となり、次のような電極反応が進行す
る。陰極（測定電極）： O₂＋4H⁺＋4e→2H₂O （酸性溶液） O₂＋2H₂O＋4e→4OH^- （中性及びアルカリ性溶液）陽極（照合電極）： 4Ag＋4Cl^-→4AgCl＋4e （広PH域）上記の陽極（照合電極）は、Ag／AgCl系を形
成して一定の電位に固定されるので、陰極もO₂
の還元に適した一定電圧に保たれ、上記の電極反
応が起こる。したがつて、陰極で電子ｅが消失し
陽極で電子ｅが発生して、陰極に到達するO₂分
子の数に比例した電流が両電極の間に流れる。陰
極に到達するO₂分子の数は測定試料中のO₂濃度
に比例するので、この電流を測定することにより
O₂濃度を知ることができる。酸素電極は電極の配置の仕方から陰陽分離型と
陰陽複合型に分類できる。前者は、両電極を測定
試料に直接浸け、試料内で電解反応を行わせるも
のである。後者は、両電極及び電解液を酸素透過
性のプラスチツクの薄膜で包み込んだものであ
る。これを測定試料に浸け、薄膜を通つたO₂を
薄膜内の電解液において電解反応を行わせるもの
である。複合型酸素電極は約10年前までは長さが直径の
数倍以上もある細長い棒状をしたものが専ら用い
られてきたが、最近では血液ガスの経皮測定（例
えば、エバーハードおよびミント、特願昭46−
76804：萩原、特願昭51−158119；萩原、特願昭
52−101235）や酸素反応容器（例えば、萩原、特
願昭61−146688）用として、長さが直径よりも短
い偏平型のものも用いられるようになつたきた。
酸素電極を分類すると第１表のようになる。 [Industrial Application Field] The present invention relates to an oxygen 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, a fixed electrode is added between the reference electrode (reference electrode, control electrode, standard electrode) and the measuring electrode, and O ₂ is electrolyzed on the surface of the measuring electrode, and the electrolytic current changes depending on the strength of the electrolytic current. TsuteO ₂
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 -0.6V with respect to the reference electrode. Therefore, approximately
When a voltage of 0.6V is applied, the reference electrode becomes an anode and the measurement electrode becomes a cathode, and the following electrode reaction proceeds. Cathode (measuring electrode): O ₂ +4H ⁺ +4e→2H ₂ O (acidic solution) O ₂ +2H ₂ O+4e→4OH ^- (neutral and alkaline solutions) Anode (reference electrode): 4Ag+4Cl ^- →4AgCl+4e (wide PH range) Above The anode (reference electrode) forms an Ag/AgCl system and is fixed at a constant potential, so the cathode is also O ₂
The electrode reaction described above takes place at a constant voltage suitable for the reduction of . Therefore, electrons e disappear at the cathode and electrons e are generated at the anode, and a current flows between the two electrodes in proportion to the number of O ₂ molecules reaching the cathode. Since the number of O ₂ molecules reaching the cathode is proportional to the O ₂ concentration in the measurement sample, by measuring this current,
You can know the O ₂ concentration. 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. The latter encloses both electrodes and the electrolyte in a thin film of oxygen-permeable plastic. This is immersed in a measurement sample, and the O ₂ that has passed through the thin film causes an electrolytic reaction in the electrolyte within the thin film. Until about 10 years ago, compound oxygen electrodes had been exclusively used in the form of long, thin rods with a length several times the diameter, but recently they have been used for transcutaneous blood gas measurement (e.g. Everhard, Mint, Special request 1977-
76804: Hagiwara, Tokugan Sho 51-158119; Hagiwara, Tokugan Sho 51-158119;
52-101235) and oxygen reaction vessels (for example, Hagiwara, Japanese Patent Application No. 61-146688), flat types with a length shorter than the diameter have also come to be used.
Table 1 shows the classification of oxygen electrodes.

【表】〓複合型〓
[Table] 〓Composite type〓

Claims

[Scope of Claims] 1. A cathode whose end surface is in contact with an 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 the cathode; A cathode reaction surface formed by one end surface, an oxygen-permeable electrode film provided to cover the reaction surface to hold electrolyte in a thin layer on the cathode reaction surface, and an electrolyte layer on the cathode reaction surface. An oxygen electrode characterized by comprising: an electrolytic solution storage section that stores an electrolytic solution at a connection position and is maintained at the same pressure as 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. Claim 2, characterized in that the cathode reaction surface is formed into a finely roughened surface.
Oxygen electrode as described in section. 4. The oxygen electrode according to claim 2, which has a porous thin film containing an electrolyte on the upper surface of the cathode reaction surface. 5 Inside the thin tube connected to the electrolyte storage section,
The oxygen electrode according to claim 1, 2, 3, or 4, characterized in that a small amount of a difficult-to-evaporate liquid is sealed. 6. Claims 1 and 2, characterized in that 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. a cathode reaction surface, an oxygen-permeable electrode film provided over the reaction surface to hold a thin layer of electrolyte on the cathode reaction surface, and an electrolyte placed at a position connected to the electrolyte layer on the cathode reaction surface. The stored electrolyte storage compartment is connected at one end to the electrolyte storage compartment and closed at the other end to adjust its interior and the interior of the electrolyte storage compartment to be slightly lower than the outside air, and to adjust this reduced pressure state to its elasticity. An oxygen electrode characterized by comprising: an elastic tube that is stably held by an elastic tube. 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 Claim 7, characterized in that a part of the electrode support is made of a thermally conductive metal and is maintained at a predetermined temperature by constant temperature heating means.
9. The oxygen electrode according to item 8 or 9.