JPH11248670A - Negative electrode for oxygen electrode - Google Patents
Negative electrode for oxygen electrodeInfo
- Publication number
- JPH11248670A JPH11248670A JP10054642A JP5464298A JPH11248670A JP H11248670 A JPH11248670 A JP H11248670A JP 10054642 A JP10054642 A JP 10054642A JP 5464298 A JP5464298 A JP 5464298A JP H11248670 A JPH11248670 A JP H11248670A
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- Japan
- Prior art keywords
- electrode
- oxygen
- cathode
- oxygen electrode
- support
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は酸素電極用陰極に関
する。詳しくは、本発明は再利用を繰り返した後におい
ても、電気化学的に安定な酸素電極を構成することが可
能な酸素電極用陰極に関する。The present invention relates to a cathode for an oxygen electrode. More specifically, the present invention relates to a cathode for an oxygen electrode capable of forming an electrochemically stable oxygen electrode even after repeated reuse.
【０００２】[0002]
【従来の技術】酸素透過性膜を透過する酸素の量を検知
用電極を用いて測定する酸素電極は、発酵プロセスの制
御、水質用の環境計測、医療分野における計測など非常
に多岐にわたる利用がなされている。近年においては、
その酸素透過性膜の外表面において酸素を消費または生
産する酵素反応と組み合わせた、酵素電極も開発されて
いる。2. Description of the Related Art Oxygen electrodes, which measure the amount of oxygen passing through an oxygen-permeable membrane using an electrode for detection, are used in a wide variety of applications, such as control of fermentation processes, environmental measurement for water quality, and measurement in the medical field. It has been done. In recent years,
Enzyme electrodes have also been developed in combination with enzymatic reactions that consume or produce oxygen on the outer surface of the oxygen permeable membrane.
【０００３】酸素電極は使用する原理から分類すると、
ポーラログラフ式、ガルバニ電池式、濃淡電池式等があ
り、各用途に応じて使い分けられている。これらのうち
ポーラログラフ式のものは、検知部となる一部の壁が酸
素透過性膜で構成された電極容器内に、電極として検知
極となる陰極、対極となる陽極、および電解質溶液を基
本的に有し、検知極に一定の電位を印加した場合に流れ
る電流を測定することにより、酸素濃度を求める形式で
ある。[0003] Oxygen electrodes are classified according to the principle used.
There are a polarographic type, a galvanic cell type, a concentration cell type, and the like, which are properly used according to each application. Of these, the polarographic type basically includes a cathode serving as a sensing electrode as an electrode, an anode serving as a counter electrode, and an electrolyte solution in an electrode container in which a part of a wall serving as a sensing unit is formed of an oxygen-permeable membrane. The oxygen concentration is determined by measuring the current flowing when a constant potential is applied to the detection electrode.
【０００４】上記の酸素電極の検知極となる陰極として
は、電極面積の規定および機械的強度の付与のため、貴
金属電極をガラス・樹脂などの支持体中に固定したもの
（以下、酸素電極用陰極とも表記する）が多用される。
公知技術の例としては、特公平１−３２９４３、特開昭
６２−６４９４２などが挙げられる。これら陰極におい
ては、上記支持体材質としては、破損の心配が無いこと
からエポキシ樹脂が使用されることが多いが、成形加工
性の観点から熱可塑性樹脂を用いる試みもされている。As a cathode serving as a detection electrode of the above-described oxygen electrode, a noble metal electrode fixed on a support such as glass or resin for the purpose of defining an electrode area and imparting mechanical strength (hereinafter referred to as an oxygen electrode) (Also referred to as a cathode) is frequently used.
Examples of known techniques include Japanese Patent Publication No. 1-39433 and Japanese Patent Application Laid-Open No. Sho 62-64942. In these cathodes, an epoxy resin is often used as the material of the support because there is no fear of breakage, but attempts have been made to use a thermoplastic resin from the viewpoint of moldability.
【０００５】[0005]
【発明が解決しようとする課題】上記ポーラログラフ式
の酸素電極は、長時間使用した場合には電解質溶液の変
質によるものと思われるが、次第に酸素応答時間が遅延
し、測定の再現性が低下してくる。このため、酸素応答
時間時間が遅延してきた場合には、酸素電極中の電解溶
液を交換したうえで、酸素電極用陰極を再使用してい
た。When the polarographic oxygen electrode is used for a long period of time, it is considered that the electrolyte solution is deteriorated. Come. For this reason, when the oxygen response time has been delayed, the cathode for the oxygen electrode has been reused after replacing the electrolytic solution in the oxygen electrode.
【０００６】しかしながら、支持体材質が熱可塑性樹脂
からなる酸素電極用陰極についてこのような再使用を繰
り返した場合には、当該酸素電極用陰極を用いた酸素電
極に電圧を印加してから測定が可能になるまでの待機時
間が長くなる、その待機時間が個々の酸素電極用陰極に
よってばらつく等の現象が起こり、酸素電極の電気化学
的安定性が低下するという問題点があった。However, when such a re-use is repeated for a cathode for an oxygen electrode whose support material is made of a thermoplastic resin, measurement is performed after applying a voltage to the oxygen electrode using the cathode for the oxygen electrode. There has been a problem that the waiting time until the oxygen electrode becomes longer becomes longer, the waiting time varies depending on the cathode for each oxygen electrode, and the electrochemical stability of the oxygen electrode is reduced.
【０００７】[0007]
【課題を解決するための手段】本発明者らは上記問題に
ついて検討を行ったところ、上記酸素電極用陰極を繰り
返し再使用した場合に生じる酸素電極の電気化学的安定
性の低下は、該酸素電極用陰極へ印加した総電気量と関
係し、かつ不可逆的に生じることがわかった。さらに、
繰り返し再使用した結果、電気化学的安定性の低い酸素
電極しか構成できなくなった酸素電極用陰極において、
貴金属電極露出部周辺の支持体を観察すると、支持体の
表面が粗になっていたり、支持体が崩壊して凹部を形成
していたりすることが確認された。Means for Solving the Problems The present inventors have studied the above problems, and found that the electrochemical stability of the oxygen electrode caused by repeatedly reusing the cathode for the oxygen electrode is reduced by the oxygen. It was found that it was related to the total amount of electricity applied to the electrode cathode and was irreversibly generated. further,
As a result of repeated reuse, in the oxygen electrode cathode where only an oxygen electrode with low electrochemical stability can be constructed,
Observation of the support around the exposed portion of the noble metal electrode confirmed that the surface of the support was rough or that the support collapsed to form a recess.
【０００８】そこで、発明者らは、これらの劣化は電気
化学的反応によって、酸素電極用陰極の貴金属電極露出
部周辺の支持体が変化したために生じたと考え、種々の
検討を行なった。その結果、支持体に耐アルカリ性を有
する樹脂を用いた場合には、酸素電極用陰極の再利用を
繰り返しても、電気化学的安定性を有する酸素電極を構
成できる場合があるという知見を得た。そして更に検討
を行なったところ、支持体材料として使用する樹脂の化
学的構造および飽和吸水率などに適切な条件があること
を見いだし、本発明を完成するに至った。Therefore, the inventors considered that such deterioration occurred due to a change in the support around the exposed portion of the noble metal electrode of the cathode for the oxygen electrode due to an electrochemical reaction, and made various studies. As a result, it was found that in the case where a resin having alkali resistance was used for the support, an oxygen electrode having electrochemical stability could be formed in some cases even when the oxygen electrode cathode was reused. . Further investigations have found that there are appropriate conditions for the chemical structure and the saturated water absorption of the resin used as the support material, and have completed the present invention.
【０００９】即ち、本発明は、支持体内に、その一部が
該支持体の表面とほぼ同一面を形成するように露出した
状態で貴金属電極が固定され、支持体外部と電気的に接
続できる酸素電極用陰極において、支持体が飽和吸水率
７％以下のポリアミド樹脂組成物で形成されていること
を特徴とする酸素電極用陰極である。That is, according to the present invention, the noble metal electrode is fixed in the support in a state where a part thereof is exposed so as to form substantially the same surface as the surface of the support, and can be electrically connected to the outside of the support. The cathode for an oxygen electrode, wherein the support is formed of a polyamide resin composition having a saturated water absorption of 7% or less.
【００１０】上記本発明の酸素電極用陰極のうち、貴金
属電極の露出部分の周辺の支持体表面に該貴金属電極の
露出部分から所定の間隔を置いて所定の空容積を有する
小室が設けられている陰極は、該陰極を用いて酸素電極
を構成した場合、電極への電圧印加後、系に流れる電流
値が一定になって測定が可能になるまでの待機時間（以
降、電流安定化時間ともいう。）が短く、しかも長時間
使用しても酸素応答時間に遅延が生じないという優れた
特性を示す。In the cathode for an oxygen electrode of the present invention, a small chamber having a predetermined empty volume is provided at a predetermined distance from the exposed portion of the noble metal electrode on the surface of the support around the exposed portion of the noble metal electrode. When the cathode is used to form an oxygen electrode, the standby time after applying a voltage to the electrode until the current flowing through the system becomes constant and measurement becomes possible (hereinafter referred to as the current stabilization time). ) Is short and oxygen response time is not delayed even if used for a long time.
【００１１】上記本発明の酸素電極用陰極を用いて、一
部の壁が酸素透過性膜により構成された電極ハウジング
（電極容器）の内部に該酸素電極用陰極、陽極及び電解
質溶液が内蔵されたポーラログラフ式酸素電極は、繰り
返し再使用した該酸素電極用陰極を使用した場合でも電
気化学的安定性が高いという特徴を有する。Using the oxygen electrode cathode of the present invention, the oxygen electrode cathode, the anode, and the electrolyte solution are incorporated in an electrode housing (electrode container) in which a part of the wall is constituted by an oxygen permeable membrane. The polarographic oxygen electrode has a feature that the electrochemical stability is high even when the repeatedly reused cathode for oxygen electrode is used.
【００１２】本発明の酸素電極用陰極では、その支持体
が飽和吸水率７％以下のポリアミド樹脂組成物で形成さ
れていることから、酸素電極を構成して電圧を印加して
も、該陰極上でおこる次式In the cathode for an oxygen electrode of the present invention, the support is formed of a polyamide resin composition having a saturated water absorption of 7% or less. The following equation that occurs above
【００１３】[0013]
【化１】 Embedded image
【００１４】で示される電気化学反応に従って該陰極の
貴金属電極露出部分で生成する水酸化物イオンに対する
耐性が高いため、支持体が劣化しにくいこと、および、
支持体の飽和吸水率が低いために電解質溶液の侵入が抑
制でき、支持体の電気絶縁性を保持しやすいことなどか
ら、酸素電極の電気化学的安定性が低下しないものと考
えられる。A high resistance to hydroxide ions generated at the exposed portion of the noble metal electrode of the cathode in accordance with the electrochemical reaction represented by
It is considered that the electrochemical stability of the oxygen electrode does not decrease because the infiltration of the electrolyte solution can be suppressed due to the low saturated water absorption of the support and the electrical insulation of the support can be easily maintained.
【００１５】[0015]
【発明の実施の形態】以下、図面を用いて本発明の酸素
電極用陰極及び本発明の酸素電極を詳細に説明するが、
本発明はこれらの添付図面に何ら限定されるものではな
い。DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the cathode for an oxygen electrode of the present invention and the oxygen electrode of the present invention will be described in detail with reference to the drawings.
The present invention is not limited to these accompanying drawings.
【００１６】まず、図１および図２を用いて本発明の酸
素電極用陰極について説明する。First, the oxygen electrode cathode of the present invention will be described with reference to FIGS.
【００１７】図１は、本発明において好適に採用される
酸素電極用陰極の断面図であり、図２は、本発明におい
て採用される酸素電極用陰極の上視図である。図１にお
いて符号１は検知極となる貴金属電極であり、その一部
（貴金属電極露出部分１ａ）は支持体２の表面とほぼ同
一面を形成するようにして露出している。ここで、貴金
属電極露出部分（以下、貴金属面とも表記する）の露出
面積は一般には１６０μｍ2〜４ｍｍ2程度である。FIG. 1 is a sectional view of a cathode for an oxygen electrode suitably used in the present invention, and FIG. 2 is a top view of a cathode for an oxygen electrode used in the present invention. In FIG. 1, reference numeral 1 denotes a noble metal electrode serving as a detection electrode, and a part thereof (a noble metal electrode exposed portion 1 a) is exposed so as to form substantially the same surface as the surface of the support 2. Here, the exposed area of the exposed portion of the noble metal electrode (hereinafter also referred to as the noble metal surface) is generally about 160 μm 2 to 4 mm 2 .
【００１８】該貴金属電極１の材質としては、金、白
金、イリジウム等が使用できるが、硬度が適度で加工が
しやすいという観点から、金を用いるのが好適である。As a material of the noble metal electrode 1, gold, platinum, iridium or the like can be used, but gold is preferably used from the viewpoint that hardness is appropriate and processing is easy.
【００１９】貴金属電極１の形状はその露出部分の露出
面が平面若しくは曲面であるものであり、且つ支持体外
部と電気的に接続するための導線が接続できる部分（接
続端子１ｂ）を有するものであればその形状は特に制限
されず任意の形状を取りうるが、本発明の酸素電極用陰
極を製造する際の生産性を勘案すると、図１に示すよう
な棒状であるのが好適である。即ち、貴金属電極が棒状
である場合には後述するインサート成形をする際の位置
ずれが起こりにくく精度の良い成形が可能となる。そし
て得られた酸素電極用陰極は、図１に示すように該接続
端子１ｂが支持体外部に突き出た態様となるため、支持
体外部と電気的に接続するための導線を接続する際の操
作性も良好である。The shape of the noble metal electrode 1 is such that the exposed surface of the exposed portion is flat or curved and has a portion (connection terminal 1b) to which a conductor for electrically connecting to the outside of the support can be connected. If so, the shape is not particularly limited, and can take any shape. However, in consideration of the productivity at the time of producing the cathode for an oxygen electrode of the present invention, a rod shape as shown in FIG. 1 is preferable. . That is, when the noble metal electrode is rod-shaped, misalignment during the insert molding described below does not easily occur, and accurate molding can be performed. The obtained cathode for an oxygen electrode has an aspect in which the connection terminal 1b protrudes out of the support as shown in FIG. 1, so that the operation for connecting a conducting wire for electrically connecting to the outside of the support is performed. The properties are also good.
【００２０】図１中、符号２は該貴金属電極を固定する
ための支持体である。当該支持体の形状は特に制限され
ないが、上記支持体２は、該支持体２に固定された貴金
属電極の露出部分が酸素透過性膜と接するようにして酸
素電極に組み込まれるため、酸素透過性膜を傷つけるこ
とのないように少なくともその酸素透過性膜と接する可
能性のある部分はゆるやかな曲面を有する形状であるの
が好ましい。In FIG. 1, reference numeral 2 denotes a support for fixing the noble metal electrode. Although the shape of the support is not particularly limited, the support 2 is incorporated into the oxygen electrode such that an exposed portion of the noble metal electrode fixed to the support 2 is in contact with the oxygen permeable membrane. It is preferable that at least a portion which may be in contact with the oxygen-permeable membrane has a shape having a gentle curved surface so as not to damage the membrane.
【００２１】支持体２の貴金属電極露出部分１ａの近傍
の表面に、該貴金属電極露出部分１ａから所定の間隔を
置いて所定の空容積を有する小室３を設けておくと、電
解質溶液の局所的な変質（導電性の低下等）を防止する
ことができ、本発明の酸素電極用陰極を用いた酸素電極
は長期安定性がより優れたものとなるため、更に好適で
ある。上記小室３は、電極ハウジングの空隙部（後述す
る図３の８）と貴金属電極露出部分１ａとの間の、小室
３を経由した拡散による、電解質溶液の供給と均質化の
バランスが適度に保たれるようなものであれば特に制限
されず、採用する電解質溶液の種類、酸素透過膜と接す
る貴金属電極や支持体部分の形状に応じて適宜決定すれ
ば良い。一般的には、図２に示すように、該貴金属電極
露出部分１ａから約０．０３〜０．５ｍｍ、より好まし
くは０．０４〜０．３ｍｍの間隔ｗを置いて、０．２〜
０．７μｌの空容積を有する小室３を、貴金属電極露出
部分を取り巻くように１〜４個配置するのが好適であ
る。ここで、上記間隔ｗとは、貴金属電極露出部１ａ周
辺と小室３周辺との最近接距離を意味し、小室３の空容
積とは、該小室３に保持し得る電解質溶液の最大量（μ
ｌ）で評価されるものである。When a small chamber 3 having a predetermined empty volume is provided at a predetermined distance from the noble metal electrode exposed portion 1a on the surface of the support 2 in the vicinity of the noble metal electrode exposed portion 1a, the local area of the electrolyte solution can be reduced. Oxygen electrode using the cathode for an oxygen electrode of the present invention can further prevent long-term stability. The small chamber 3 appropriately balances the supply of the electrolyte solution and the homogenization by diffusion through the small chamber 3 between the gap (8 in FIG. 3 described later) of the electrode housing and the exposed portion 1a of the noble metal electrode. There is no particular limitation as long as it is dripping, and it may be appropriately determined according to the type of the electrolyte solution to be used, the shape of the noble metal electrode in contact with the oxygen permeable membrane, and the shape of the support. Generally, as shown in FIG. 2, a distance w of about 0.03 to 0.5 mm, more preferably 0.04 to 0.3 mm from the noble metal electrode exposed portion 1a,
It is preferable to arrange 1 to 4 small chambers 3 having an empty volume of 0.7 μl so as to surround the exposed portion of the noble metal electrode. Here, the interval w means the closest distance between the periphery of the noble metal electrode exposed portion 1a and the periphery of the small chamber 3, and the empty volume of the small chamber 3 is the maximum amount of electrolyte solution (μ) that can be held in the small chamber 3.
1).
【００２２】なお、前記したように、この様な小室を設
けない場合でも、本発明の酸素電極用陰極においては繰
り返し再使用したものを用いて酸素電極を構成しても該
酸素電極の電気化学的安定性を低下させないという効果
は得られる。As described above, even when such a small chamber is not provided, even if an oxygen electrode is formed by repeatedly using the cathode for an oxygen electrode of the present invention, the electrochemical The effect of not lowering the stability is obtained.
【００２３】本発明の酸素電極用陰極における最大の特
徴は、上記支持体２に、飽和吸水率７％以下のポリアミ
ド樹脂組成物を用いることにある。ここで、飽和吸水率
とは、３７℃の水中に樹脂片を浸漬し、当該樹脂片の重
量が変化しなくなるまで放置した後の重量増加率を意味
する。The most significant feature of the cathode for an oxygen electrode of the present invention resides in that the support 2 is made of a polyamide resin composition having a saturated water absorption of 7% or less. Here, the saturated water absorption means the rate of weight increase after immersing a resin piece in water at 37 ° C. and allowing it to stand until the weight of the resin piece no longer changes.
【００２４】支持体としてポリアミド樹脂組成物以外の
材質を用いた場合には、貴金属電極露出部分から発生し
た水酸化物イオンにより貴金属電極露出部分周辺の支持
体が分解し、繰り返し再使用した該酸素電極用陰極を用
いた酸素電極の電気化学的安定性が低下する。さらに、
この場合には、貴金属電極と良好な密着をすることが難
しく、支持体としての機能を発揮できないことがあった
り、特に支持体材質の疎水性が高すぎる場合には貴金属
電極露出部分周辺の電解質溶液の保持量が低下して電極
として機能しなくなることがある。When a material other than the polyamide resin composition is used as the support, hydroxide around the exposed portion of the noble metal electrode is decomposed by hydroxide ions generated from the exposed portion of the noble metal electrode, and the oxygen which is repeatedly reused is used. The electrochemical stability of the oxygen electrode using the electrode cathode decreases. further,
In this case, it is difficult to make good contact with the noble metal electrode, and the function of the support may not be exhibited. In some cases, the retained amount of the solution is reduced and the electrode cannot function as an electrode.
【００２５】また、支持体の材質がポリアミド樹脂組成
物であっても、その飽和吸水率が７％を越える場合に
は、酸素電極のハイジング内の空隙部に納められている
電解質溶液が支持体内に侵入し、電気絶縁性が低下して
測定精度が低下する。[0025] Even if the material of the support is a polyamide resin composition, if the saturated water absorption exceeds 7%, the electrolyte solution contained in the voids in the heasing of the oxygen electrode is filled with the electrolyte solution. , The electrical insulation is reduced, and the measurement accuracy is reduced.
【００２６】本発明で使用する飽和吸水率７％以下のポ
リアミド樹脂組成物は、ポリアミド樹脂を主成分とする
樹脂の組成物であって、飽和吸水率が７％以下の組成物
であれば特に限定されない。具体的にはポリアミドＭＸ
Ｄ６、ポリアミド１１、ポリアミド１２等の飽和吸水率
７％以下のポリアミド系高分子単独、又は該飽和吸水率
７％以下のポリアミド系高分子および／若しくはポリア
ミド６１２、ポリアミド６１０、ポリアミド６６等の飽
和吸水率が７％を越えるポリアミド系高分子にガラス繊
維、ガラス粒子、シリカ等の充填剤を添加して全体の飽
和吸水率になるように調整した混合物等が使用できる。The polyamide resin composition having a saturated water absorption of 7% or less used in the present invention is a resin composition containing a polyamide resin as a main component and particularly a composition having a saturated water absorption of 7% or less. Not limited. Specifically, polyamide MX
D6, polyamide 11 or polyamide 12 alone or other polyamide-based polymer having a saturated water absorption of 7% or less, or polyamide-based polymer having a saturated water absorption of 7% or less and / or saturated water absorption of polyamide 612, polyamide 610, polyamide 66, etc. A mixture prepared by adding a filler such as glass fiber, glass particles, or silica to a polyamide-based polymer having a ratio of more than 7% to adjust the total saturated water absorption can be used.
【００２７】さらに、本発明で使用する上記ポリアミド
樹脂組成物は、絶縁性、低酸素透過性も備えていること
が好ましい。絶縁性においては、３７℃の水中における
体積抵抗率が１０10Ω・ｃｍ以上、酸素電極のノイズを
減少させ充分な感度を得るために、さらに好ましくは１
０11Ω・ｃｍ以上を有するものが適する。低酸素透過性
においては、相対湿度５０％のときの酸素透過度が５ｃ
ｍ3・ｃｍ・ｍ-2・２４hr-1・atm-1以下、さらに好まし
くは、３ｃｍ3・ｃｍ・ｍ-2・２４hr-1・atm- 1以下のも
のが適する。これらの条件を満たす組成物の例として
は、飽和吸水率７％以下の前記ポリアミド系高分子にガ
ラス繊維等の前記充填剤を混合した組成物、及び該組成
物に全体の飽和吸水率が７％以下となる範囲で飽和吸水
率が７％を越える前記ポリアミド系高分子を加えた組成
物等が挙げられる。Further, the polyamide resin composition used in the present invention preferably has insulating properties and low oxygen permeability. As for the insulating property, the volume resistivity in water at 37 ° C. is 10 10 Ω · cm or more.
Those having 0 11 Ω · cm or more are suitable. In low oxygen permeability, the oxygen permeability at a relative humidity of 50% is 5c.
m 3 · cm · m -2 · 24hr -1 · atm -1 or less, more preferably, 3cm 3 · cm · m -2 · 24hr -1 · atm - 1 the following ones are suitable. Examples of the composition satisfying these conditions include a composition in which the filler such as glass fiber is mixed with the polyamide-based polymer having a saturated water absorption of 7% or less, and a composition having an overall saturated water absorption of 7%. %, And a composition to which the above-mentioned polyamide polymer having a saturated water absorption of more than 7% is added.
【００２８】当該酸素電極用陰極の成形方法は特に制限
されず、あらかじめ貴金属電極を飽和吸水率７％以下の
ポリアミド樹脂組成物に固定させた後に樹脂塊を切削し
て成形する方法、支持体に貴金属電極を後ろから装着す
る方法、および貴金属電極の固定と支持体形状の形成と
を同時に行なう方法などの何れの方法を採用しても良
い。The method of forming the cathode for an oxygen electrode is not particularly limited, and a method of fixing a noble metal electrode in advance to a polyamide resin composition having a saturated water absorption of 7% or less, cutting a resin mass, and forming the support. Any method such as a method of attaching the noble metal electrode from behind, and a method of simultaneously fixing the noble metal electrode and forming the shape of the support may be adopted.
【００２９】これらの製造方法の中でも、成形精度、量
産性等の観点から、支持体形状が形成できるような金型
内に検知極となる貴金属電極を予めセットしておき、溶
融した飽和吸水率７％以下のポリアミド樹脂組成物を注
入して一体成形する、いわゆるインサート成形を採用す
るのが好適である。このとき、貴金属電極としては、相
対湿度９０％の雰囲気下で２０〜６５℃の温度変化サイ
クルを繰り返しながら直流１００Ｖの電圧を７日間印加
したときに、体積抵抗率が１．０×１０11Ω・ｃｍ以上
を示すエポキシ系樹脂、不飽和ポリエステル系樹脂、ポ
リイミド系樹脂等の絶縁性樹脂がその側面に１３〜２７
μｍの厚さで塗布された貴金属棒を用いると、貴金属棒
と支持体との密着性が向上するので特に好適である。Among these manufacturing methods, a noble metal electrode serving as a detection electrode is set in advance in a mold capable of forming a support shape from the viewpoint of molding accuracy, mass productivity, etc. It is preferable to employ so-called insert molding in which a polyamide resin composition of 7% or less is injected and integrally molded. At this time, the volume resistivity of the noble metal electrode was 1.0 × 10 11 Ω when a voltage of DC 100 V was applied for 7 days while repeating a temperature change cycle of 20 to 65 ° C. in an atmosphere of a relative humidity of 90%. Insulating resin such as an epoxy resin, an unsaturated polyester resin, a polyimide resin, and the like having a size of 13 cm or more
It is particularly preferable to use a noble metal rod coated with a thickness of μm because the adhesion between the noble metal rod and the support is improved.
【００３０】上記インサート成形における成形条件は、
支持体となるポリアミド樹脂組成物の種類に応じて、通
常採用される条件の中から最適な条件を適宜決定すれば
よい。The molding conditions in the insert molding are as follows:
Depending on the type of the polyamide resin composition to be used as a support, optimal conditions may be appropriately determined from conditions usually employed.
【００３１】本発明の酸素電極用陰極は、一部の壁が酸
素透過性膜で構成された電極ハウジング内に対極となる
陽極と共に内蔵させ、更に該電極ハウジング内に電解質
溶液を封入することにより気体又は液体中の酸素分圧
（酸素濃度）を測定するためのポーラログラフ式酸素電
極を構成することが出来る。また、上記構成のポーラロ
グラフ式酸素電極において、酸素透過膜の外表面にグル
コースオキシダーゼ、ウリカーゼなどの酵素を固定化す
ることにより、酵素センサーを構成し、発酵プロセスの
制御、水質などの環境計測、医療分野における計測、酵
素センサーなどへ応用することが可能である。なお、こ
のとき固定化される酵素及びその固定方法は特に限定さ
れず、従来の酵素センサーで一般的に使用されている酵
素及び固定化方法が何等制限なく使用できる。The cathode for an oxygen electrode of the present invention is obtained by incorporating an anode serving as a counter electrode in an electrode housing having a part of a wall made of an oxygen-permeable membrane, and further sealing an electrolyte solution in the electrode housing. A polarographic oxygen electrode for measuring the oxygen partial pressure (oxygen concentration) in a gas or liquid can be configured. Further, in the polarographic oxygen electrode having the above configuration, an enzyme sensor such as glucose oxidase and uricase is immobilized on the outer surface of the oxygen-permeable membrane, thereby forming an enzyme sensor, controlling a fermentation process, measuring environmental conditions such as water quality, and medical care. It can be applied to measurement, enzyme sensor, etc. in the field. The enzyme to be immobilized at this time and the method for immobilizing the enzyme are not particularly limited, and enzymes and immobilization methods generally used in conventional enzyme sensors can be used without any limitation.
【００３２】以下、本発明の酸素電極用陰極の用途の応
用例として該酸素電極用陰極を用いて構成したポーラロ
グラフ式酸素電極（以下、本発明の酸素電極ともいう）
について、図３を用いて更に詳しく説明する。Hereinafter, as an application example of the use of the cathode for an oxygen electrode of the present invention, a polarographic oxygen electrode constituted by using the cathode for an oxygen electrode (hereinafter also referred to as the oxygen electrode of the present invention).
Will be described in more detail with reference to FIG.
【００３３】図３は、本発明の酸素電極の代表的な構造
を示す断面図である。図３において符号４は電極ハウジ
ングでありその一部は酸素透過性膜７で構成されてい
る。また、該電極ハウジング４の中には、本発明の酸素
電極用陰極５及び対極となる陽極６が内蔵されており、
更にその空隙部には電解質溶液８が封入されている。な
お、該電解質溶液８はその大部分は電極ハウジング４と
酸素電極用陰極５の間の空隙部に存在しているが、その
一部は小室３内部、及び酸素電極用陰極５と酸素透過性
膜７との界面に存在している。また、本発明の酸素電極
に内蔵される本発明の酸素電極用陰極５と陽極６とは電
源９及び電流計１０を介在して電気的に接続している。FIG. 3 is a sectional view showing a typical structure of the oxygen electrode of the present invention. In FIG. 3, reference numeral 4 denotes an electrode housing, a part of which is constituted by an oxygen-permeable membrane 7. In the electrode housing 4, a cathode 5 for an oxygen electrode of the present invention and an anode 6 serving as a counter electrode are incorporated.
Further, an electrolyte solution 8 is sealed in the gap. The electrolyte solution 8 is mostly present in the gap between the electrode housing 4 and the cathode 5 for the oxygen electrode, but part of the electrolyte solution 8 is in the small chamber 3 and between the cathode 5 for the oxygen electrode and the oxygen permeable cathode. It is present at the interface with the film 7. Further, the cathode 5 for an oxygen electrode of the present invention and the anode 6 incorporated in the oxygen electrode of the present invention are electrically connected via a power supply 9 and an ammeter 10.
【００３４】本発明における電極ハウジング４は、検知
部の壁が酸素透過性膜７で構成され、電解質溶液を封入
できる容器であれば特に限定されるものではないが、図
３に示すように、筒状の容器の先端部を酸素透過性膜で
構成した構造が一般的である。The electrode housing 4 of the present invention is not particularly limited as long as the wall of the detecting portion is formed of the oxygen-permeable membrane 7 and can be filled with an electrolyte solution. A structure in which the tip of a cylindrical container is formed of an oxygen-permeable membrane is common.
【００３５】上記電極ハウジング４を構成する酸素透過
性膜７以外の部分の材質としては、中に封入する電解質
溶液に対して耐性を有する公知の材質の中から適宜選択
することができる。このような材質としては、たとえ
ば、ガラス、セラミックスなどの無機物、ポリアセター
ル、ポリ塩化ビニル、エポキシ樹脂等の合成樹脂等が挙
げられる。The material of the portion other than the oxygen-permeable membrane 7 constituting the electrode housing 4 can be appropriately selected from known materials having resistance to the electrolyte solution sealed therein. Examples of such a material include inorganic substances such as glass and ceramics, and synthetic resins such as polyacetal, polyvinyl chloride, and epoxy resin.
【００３６】また、酸素透過性膜７の材質は、液体を透
過せず且つ酸素を透過しうる能力を有するものであれば
特に制限されないが、相対湿度５０％のときの酸素透過
度が１０ｃｍ3・ｃｍ・ｍ-2・２４hr-1・atm-1以上、さ
らに好ましくは１７ｃｍ3・ｃｍ・ｍ-2・２４hr-1・atm
-1以上の樹脂が適する。これらの条件を満たす樹脂の例
としては、ポリテトラフルオロエチレン、テトラフルオ
ロエチレン−ヘキサフルオロプロピレン共重合体等のフ
ッ素樹脂、ポリスチレン、ポリプロピレン、ポリカーボ
ネート、ポリエチレン、ポリフェニレンオキサイド、ポ
リメチルペンテン等が一般的に挙げられる。これらのう
ち、酸素透過性が高く、かつ柔軟性のある膜が得られる
フッ素樹脂が特に好適である。The material of the oxygen permeable membrane 7 is not particularly limited as long as it has the ability to permeate a liquid and permeate oxygen, but the oxygen permeability at a relative humidity of 50% is 10 cm 3.・ Cm ・ m -2・ 24hr -1・ atm -1 or more, more preferably 17cm 3・ cm ・ m -2・ 24hr -1・ atm
A resin of -1 or more is suitable. Examples of resins satisfying these conditions include polytetrafluoroethylene, fluororesins such as tetrafluoroethylene-hexafluoropropylene copolymer, polystyrene, polypropylene, polycarbonate, polyethylene, polyphenylene oxide, and polymethylpentene. No. Among these, a fluororesin having a high oxygen permeability and a flexible film is particularly preferable.
【００３７】上記酸素透過性膜の厚さには特に制限はな
いが、透過した酸素を定電位電解電流で検知する上から
１〜１００μｍとすることが好ましく、膜の取り扱いや
すさも加味すると特に１０〜５０μｍとすることが好ま
しい。The thickness of the oxygen permeable membrane is not particularly limited, but is preferably 1 to 100 μm from the viewpoint of detecting the permeated oxygen by a constant potential electrolysis current. It is preferable to set it to 50 μm.
【００３８】本発明において、酸素分圧（酸素濃度）測
定のためには、検知極となる陰極が固定された酸素電極
用陰極５の他に、対極となる陽極６が必要である。すな
わち、測定系は電気化学的反応により酸素を電気分解す
るための電極である陰極の他に、上記電気化学反応を進
行させるための回路を構成する陽極を必要とする。陽極
は公知の電極の中から選択して適宜使用することができ
るが、簡便性や生成する化合物の有害性などの見地か
ら、銀電極が好適に使用される。In the present invention, in order to measure the oxygen partial pressure (oxygen concentration), an anode 6 serving as a counter electrode is required in addition to the cathode 5 for an oxygen electrode to which a cathode serving as a detection electrode is fixed. That is, the measurement system needs an anode constituting a circuit for promoting the electrochemical reaction in addition to a cathode which is an electrode for electrolyzing oxygen by an electrochemical reaction. The anode can be selected from known electrodes and used as appropriate, but a silver electrode is preferably used from the viewpoint of simplicity and harmfulness of the compound to be formed.
【００３９】また、本発明における酸素分圧（酸素濃
度）測定のための他の構造及び使用の態様は、公知の態
様が特に制限なく採用される。例えば、検知極は電流計
を介して対極と電気的に接続される。In the present invention, known structures and other modes for measuring the oxygen partial pressure (oxygen concentration) are not particularly limited. For example, the sensing electrode is electrically connected to a counter electrode via an ammeter.
【００４０】上記した電極ハウジング内に封入される電
解質溶液８としては、通常のポーラログラフ式酸素電極
で使用される塩化カリウム、塩化ナトリウム、臭化ナト
リウムなどのアルカリ金属塩を含む水溶液電解質溶液を
何ら制限無く使用することができる。The electrolyte solution 8 sealed in the electrode housing is not limited to an aqueous electrolyte solution containing an alkali metal salt such as potassium chloride, sodium chloride or sodium bromide used in a usual polarographic oxygen electrode. Can be used without.
【００４１】本発明の酸素電極を用いて気体または液体
試料中の酸素分圧（酸素濃度）を測定する方法は従来の
ポーラログラフ式酸素電極を用いた測定方法と変わる点
は特になく、例えば次のようにして行うことが出来る。
即ち、まず、上記のようにして構成した酸素電極の陰極
へ、対極に対して−０．８Ｖを印加し、両電極間に流れ
る電流値が一定になるまで待機した後に、該酸素電極の
酸素透過性膜外表面に酸素分圧（酸素濃度）が既知の液
体または気体を接触させ、系に流れた電流値を電流計で
計測して基準とする。次に、酸素分圧（酸素濃度）を測
定しようとする気体および液体を同様に該酸素透過性膜
外表面に接触させ、その時の電流値を計測する。これを
前出の基準と比較することにより、酸素分圧（酸素濃
度）の測定を行うことが出来る。The method for measuring the oxygen partial pressure (oxygen concentration) in a gas or liquid sample using the oxygen electrode of the present invention is not particularly different from the conventional method using a polarographic oxygen electrode. It can be done as follows.
That is, first, -0.8 V is applied to the cathode of the oxygen electrode configured as described above with respect to the counter electrode, and the system waits until the value of the current flowing between both electrodes becomes constant. A liquid or gas having a known oxygen partial pressure (oxygen concentration) is brought into contact with the outer surface of the permeable membrane, and the value of the current flowing through the system is measured by an ammeter and used as a reference. Next, a gas or liquid whose oxygen partial pressure (oxygen concentration) is to be measured is similarly brought into contact with the outer surface of the oxygen-permeable membrane, and the current value at that time is measured. By comparing this with the aforementioned reference, the oxygen partial pressure (oxygen concentration) can be measured.
【００４２】[0042]
【実施例】以下に本発明を更に具体的に説明するために
実施例を挙げるが、本発明はこれらの実施例に限定され
るものではない。EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.
【００４３】実施例１及び２ まず、貴金属電極として、直径１ｍｍの金棒に熱硬化型
エポキシ樹脂を約１５μｍの厚さに塗布したものを作製
した。次に、貴金属電極露出部分との間隔（ｗ）が約
０．２ｍｍであり、空容積が約０．４μｌの小室が、貴
金属電極露出部分をとりまくように４個配置できるよう
な金型内に、該貴金属電極を挿入した。さらに、該金型
内に溶融したポリアミド１２（ガラス繊維を混合して飽
和吸水率０．９％に調整したもの、実施例１）又はポリ
アミドＭＸＤ６（ガラス繊維を混合して飽和吸水率２．
４％に調整したもの、実施例２）を圧入した後冷却し
て、外径６．５ｍｍで支持体全長２７ｍｍである、図１
に示すような形状の各種の酸素電極用陰極を作製した。Examples 1 and 2 First, a noble metal electrode was prepared by applying a thermosetting epoxy resin to a metal rod having a diameter of 1 mm to a thickness of about 15 μm. Next, the space (w) between the exposed portion of the noble metal electrode is about 0.2 mm, and a small chamber having an empty volume of about 0.4 μl is placed in a mold in which four small chambers can be arranged so as to surround the exposed portion of the noble metal electrode. The noble metal electrode was inserted. Furthermore, the polyamide 12 melted in the mold (mixed with glass fibers and adjusted to a saturated water absorption of 0.9%, Example 1) or polyamide MXD6 (mixed with glass fibers and saturated water absorption 2.
After adjusting the pressure to 4%, Example 2) was press-fitted and cooled, and the outer diameter was 6.5 mm and the total length of the support was 27 mm.
Various types of cathodes for oxygen electrodes having the shapes shown in FIG.
【００４４】次に、これらの酸素電極用陰極を用いて図
３に示す構造の酸素電極を構成した。即ち、内径１０ｍ
ｍの電極ハウジングの中に酸素電極用陰極と対極となる
直径１ｍｍの銀線を設置するとともに、酸素透過膜とし
て厚さ約２５μｍのポリテトラフルオロエチレンフィル
ムを配置し、さらに、電極ハウジング内に表１に示す組
成の電解質溶液を封入した。Next, an oxygen electrode having the structure shown in FIG. 3 was constructed using these cathodes for an oxygen electrode. That is, inner diameter 10m
A silver wire having a diameter of 1 mm, which is a counter electrode to the cathode for an oxygen electrode, is placed in an electrode housing having a thickness of about 25 μm, and a polytetrafluoroethylene film having a thickness of about 25 μm is disposed as an oxygen permeable membrane. An electrolyte solution having the composition shown in FIG.
【００４５】[0045]
【表１】 [Table 1]
【００４６】上記のように作製した酸素電極を各樹脂に
ついて２本ずつ用意し、３７℃保温下で陰極へ、陽極に
対して−０．８Ｖの電圧を印加し続けた。一定期間毎に
当該酸素電極の一部を解体し、貴金属電極露出部分の研
磨や電解質溶液および酸素透過性膜の交換等を行なっ
て、再び酸素電極を構成した（以下、この繰り返しを、
再使用サイクルとも表記する）。そして、初期及び再使
用サイクルを経る毎に測定した印加後の電流値から、標
準的な使用状況下で再使用された本発明の酸素電極用陰
極が、印加後６０分以内に酸素分圧（酸素濃度）測定が
できる、充分に電気化学的安定性の高い酸素電極を構成
できるような期間（以下、酸素電極用陰極の再利用可能
期間とも表記する）を算出した。この結果を表２に示
す。Two oxygen electrodes prepared as described above were prepared for each resin, and a voltage of -0.8 V was continuously applied to the cathode while maintaining the temperature at 37 ° C. At regular intervals, a part of the oxygen electrode was disassembled, the exposed portion of the noble metal electrode was polished, the electrolyte solution and the oxygen permeable membrane were exchanged, and the like, to form an oxygen electrode again (hereinafter, this repetition was repeated.
Also referred to as a reuse cycle). Then, based on the current value after application measured each time through the initial and reuse cycles, the oxygen electrode cathode of the present invention reused under standard use conditions shows that the oxygen partial pressure ( A period (hereinafter, also referred to as a reusable period of a cathode for an oxygen electrode) was calculated in which an oxygen electrode capable of measuring (oxygen concentration) and having a sufficiently high electrochemical stability could be formed. Table 2 shows the results.
【００４７】[0047]
【表２】 [Table 2]
【００４８】比較例１及び２ 酸素電極用陰極の支持体材質としてポリエチレンテレフ
タレート（比較例１）またはポリサルフォン（比較例
２）を用いること以外は実施例１と同様にして酸素電極
を作製し、実施例と同様にして電流値変化速度の測定と
酸素電極の再利用可能期間への換算を行なった。その結
果を表２に示す。Comparative Examples 1 and 2 An oxygen electrode was prepared and manufactured in the same manner as in Example 1 except that polyethylene terephthalate (Comparative Example 1) or polysulfone (Comparative Example 2) was used as a support material of the cathode for an oxygen electrode. In the same manner as in the example, the measurement of the current value change rate and the conversion to the reusable period of the oxygen electrode were performed. Table 2 shows the results.
【００４９】比較例３ 酸素電極用陰極の支持体材質として飽和吸水率が８．９
％のポリアミド４６を使用する以外は実施例１と同様に
して酸素電極を作製した。作製した酸素電極を室温で３
日保存後に電圧を印加したところ短絡していた。Comparative Example 3 A saturated water absorption of 8.9 was used as a support material of the cathode for an oxygen electrode.
%, And an oxygen electrode was produced in the same manner as in Example 1 except that polyamide 46 was used. Prepare the oxygen electrode at room temperature
When a voltage was applied after storage for a day, a short circuit occurred.
【００５０】[0050]
【発明の効果】本発明の酸素電極用陰極は、酸素電極用
陰極の再使用を繰り返した後においても、電気化学的に
安定な酸素電極を構成することが可能である。According to the cathode for an oxygen electrode of the present invention, an electrochemically stable oxygen electrode can be formed even after reusing the cathode for an oxygen electrode.
【図面の簡単な説明】[Brief description of the drawings]
【図１】本発明の酸素電極用陰極の断面図である。FIG. 1 is a cross-sectional view of a cathode for an oxygen electrode of the present invention.
【図２】本発明の酸素電極用陰極の上視図である。FIG. 2 is a top view of a cathode for an oxygen electrode of the present invention.
【図３】本発明の酸素電極の断面図である。FIG. 3 is a cross-sectional view of the oxygen electrode of the present invention.
１ 貴金属電極 １ａ 貴金属電極露出部分 １ｂ 接続端子 ２ 支持体 ３ 小室 ４ 電極ハウジング ５ 本発明の酸素電極用陰極 ６ 陽極 ７ 酸素透過性膜 ８ 電解質溶液 ９ 電源 １０ 電流計 DESCRIPTION OF SYMBOLS 1 Noble metal electrode 1a Noble metal electrode exposed part 1b Connection terminal 2 Support 3 Small chamber 4 Electrode housing 5 Cathode for oxygen electrode of the present invention 6 Anode 7 Oxygen permeable membrane 8 Electrolyte solution 9 Power supply 10 Ammeter
Claims (4)
とほぼ同一面を形成するように露出した状態で貴金属電
極が固定され、支持体外部と電気的に接続できる酸素電
極用陰極において、支持体が飽和吸水率７％以下のポリ
アミド樹脂組成物で形成されていることを特徴とする酸
素電極用陰極。1. A cathode for an oxygen electrode to which a noble metal electrode is fixed in a state in which a part of the noble metal electrode is exposed so as to form substantially the same surface as the surface of the support, and which can be electrically connected to the outside of the support. 3. The cathode for an oxygen electrode according to claim 1, wherein the support is formed of a polyamide resin composition having a saturated water absorption of 7% or less.
面に該貴金属電極の露出部分から所定の間隔を置いて所
定の空容積を有する小室が設けられていることを特徴と
する請求項１記載の酸素電極用陰極。2. A small chamber having a predetermined empty volume is provided at a predetermined distance from the exposed portion of the noble metal electrode on the surface of the support around the exposed portion of the noble metal electrode. The cathode for an oxygen electrode according to the above.
内に挿入し、次いで該金型内に溶融した飽和吸水率７％
以下のポリアミド樹脂組成物を導入してインサート成形
することを特徴とする請求項１または２記載の酸素電極
用陰極の製造方法。3. A noble metal rod coated with an insulating resin is inserted into a mold, and then a saturated water absorption rate of 7% melted in the mold.
The method for producing a cathode for an oxygen electrode according to claim 1 or 2, wherein insert molding is performed by introducing the following polyamide resin composition.
た電極ハウジングの内部に陰極、陽極及び電解質溶液が
内蔵されたポーラログラフ式酸素電極において、陰極が
請求項１又は請求項２記載の酸素電極用陰極であること
を特徴とするポーラログラフ式酸素電極。4. A polarographic oxygen electrode in which a cathode, an anode, and an electrolyte solution are incorporated inside an electrode housing having a part of a wall formed of an oxygen-permeable membrane, wherein the cathode is according to claim 1 or 2. A polarographic oxygen electrode, which is a cathode for an oxygen electrode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05464298A JP3838774B2 (en) | 1998-03-06 | 1998-03-06 | Cathode for oxygen electrode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05464298A JP3838774B2 (en) | 1998-03-06 | 1998-03-06 | Cathode for oxygen electrode |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11248670A true JPH11248670A (en) | 1999-09-17 |
| JP3838774B2 JP3838774B2 (en) | 2006-10-25 |
Family
ID=12976440
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP05464298A Expired - Fee Related JP3838774B2 (en) | 1998-03-06 | 1998-03-06 | Cathode for oxygen electrode |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3838774B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002195975A (en) * | 2000-12-22 | 2002-07-10 | Dkk Toa Corp | Membrane-type electrode |
| JP2006098390A (en) * | 2004-09-01 | 2006-04-13 | Otomo Teruo | Indicator electrode used for electrochemical measurement of liquid |
-
1998
- 1998-03-06 JP JP05464298A patent/JP3838774B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002195975A (en) * | 2000-12-22 | 2002-07-10 | Dkk Toa Corp | Membrane-type electrode |
| JP2006098390A (en) * | 2004-09-01 | 2006-04-13 | Otomo Teruo | Indicator electrode used for electrochemical measurement of liquid |
| JP4742727B2 (en) * | 2004-09-01 | 2011-08-10 | 大友 照夫 | Indicator electrode used for redox potential measurement |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3838774B2 (en) | 2006-10-25 |
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