JP3813606B2 - Combined electrode of electrolysis electrode and redox potential measurement electrode - Google Patents

Combined electrode of electrolysis electrode and redox potential measurement electrode Download PDF

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JP3813606B2
JP3813606B2 JP2003388081A JP2003388081A JP3813606B2 JP 3813606 B2 JP3813606 B2 JP 3813606B2 JP 2003388081 A JP2003388081 A JP 2003388081A JP 2003388081 A JP2003388081 A JP 2003388081A JP 3813606 B2 JP3813606 B2 JP 3813606B2
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格図 朝
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本発明は、電気分解を行なう電極と酸化還元電位を測定する電極を一体化した電極及び該電極により、所定の酸化還元電位を示すヨウ化物イオン及び三ヨウ化物イオンを含む溶液を生成し、次いで試料を投入して酸化還元電位を測定し、それらの酸化還元電位の変化量から、試料中の過酢酸及び／又は過酸化水素若しくは次亜塩素酸又はその塩、ヨウ化物（塩化ヨウ素等）等の濃度を測定する方法に関する。   According to the present invention, an electrode in which an electrode for electrolysis and an electrode for measuring a redox potential are integrated and a solution containing iodide ions and triiodide ions exhibiting a predetermined redox potential is generated by the electrodes, Measure the redox potential by putting the sample in, and based on the amount of change in the redox potential, peracetic acid and / or hydrogen peroxide or hypochlorous acid or its salt, iodide (iodine chloride, etc.), etc. The present invention relates to a method for measuring the concentration.

食品業界において、食品やそれを入れる容器等の衛生管理が重要であり、それらを殺菌、滅菌するために、過酢酸、過酸化水素、次亜塩素酸ソーダ、ヨウ化物（塩化ヨウ素等）等の水溶液が、広く使用されている。そのために、それら水溶液中の過酢酸、過酸化水素、次亜塩素酸塩、ヨウ化物等の濃度を迅速に測定する必要があり、種々の電気化学的な測定法が知られている。   In the food industry, hygiene management of food and its containers is important, and in order to sterilize and sterilize them, peracetic acid, hydrogen peroxide, sodium hypochlorite, iodide (iodine chloride, etc.) Aqueous solutions are widely used. Therefore, it is necessary to rapidly measure the concentration of peracetic acid, hydrogen peroxide, hypochlorite, iodide, etc. in these aqueous solutions, and various electrochemical measurement methods are known.

例えば、特許文献１には、金、白金等の作用電極、補助電極、参照電極を用いたフローセルを使用して、電流値を測定することにより、試料中の過酢酸及び過酸化水素を分別定量する方法が記載されている。
また、特許文献２には、金、白金、カーボン等の作用電極、参照電極、白金の対極電極からなる３極の電極方式により、酸化還元電位の変化量を測定して、試料中の過酢酸及び過酸化水素を分別定量する方法が記載されている。この方法では、測定のためにヨウ化物イオン、ヨウ素を含む酢酸緩衝液を使用し、ヨウ化物イオン、ヨウ素の濃度を別途測定する必要がある。また、この緩衝液は、ヨウ素が光や温度により影響されるので、その保存が困難である。 For example, Patent Document 1 discloses the determination of peracetic acid and hydrogen peroxide in a sample by measuring a current value using a flow cell using a working electrode such as gold and platinum, an auxiliary electrode, and a reference electrode. How to do is described.
In Patent Document 2, the amount of change in redox potential is measured by a tripolar electrode system comprising a working electrode such as gold, platinum, and carbon, a reference electrode, and a counter electrode of platinum, and peracetic acid in a sample is measured. And a method for the fractional quantification of hydrogen peroxide. In this method, it is necessary to use an acetate buffer containing iodide ions and iodine for measurement, and separately measure the concentrations of iodide ions and iodine. Further, this buffer solution is difficult to preserve because iodine is affected by light and temperature.

さらに、市販の過酢酸測定装置として自動測定装置があり、測定セル中に、電気分解用の電解電極と、白金電極と比較電極からなる検出電極が、それぞれ独立して設置されている。この方法は、ヨウ化カリウムを含む緩衝液を電気分解により一定の酸化還元電位に調節して、それに試料を投入して得られる酸化還元電位の変化量から濃度を測定する。   Furthermore, there is an automatic measuring device as a commercially available peracetic acid measuring device, and an electrolytic electrode for electrolysis and a detection electrode composed of a platinum electrode and a reference electrode are installed independently in the measuring cell. In this method, a buffer solution containing potassium iodide is adjusted to a constant oxidation-reduction potential by electrolysis, and the concentration is measured from the amount of change in oxidation-reduction potential obtained by introducing a sample thereto.

ヨウ素及びヨウ化物イオンを含む緩衝溶液を用いて、酸化還元電位を測定して、過酢酸、過酸化水素の濃度を測定する場合、分析精度を上げるためには、ヨウ化物イオンと三ヨウ化物イオン濃度の初期値を正確に求めることが重要である。これらの値を正確に得るには、試料の測定ごとに、所定の濃度のヨウ化カリウム酢酸緩衝溶液を用い、電気分解等によりヨウ化物イオンを酸化して、その溶液の酸化還元電位を一定に制御することによって達成される。   When measuring the oxidation-reduction potential using a buffer solution containing iodine and iodide ions, and measuring the concentration of peracetic acid and hydrogen peroxide, iodide ions and triiodide ions are used to increase the analytical accuracy. It is important to accurately determine the initial value of concentration. To obtain these values accurately, use a potassium iodide acetate solution with a predetermined concentration for each measurement of the sample, oxidize iodide ions by electrolysis, etc., and keep the redox potential of the solution constant. Achieved by controlling.

電気分解により酸化還元電位を一定にするために、溶液の酸化還元電位をモニターしながら電気分解の電流を制御する必要があるが、電気分解のための電極と酸化還元電位を測定する電極を独立して測定セルに入れて、電解電極に電位を加え電解して一定の酸化還元電位に調整するには、各電極の相対的位置により、電極付近の溶液に電位勾配が生じるので、酸化還元電位は複雑な挙動を示し、電流値の制御が困難である。
また、独立した数本の電極を測定するセルに投入するのでは、測定セルの容量が大きくなり、反応が均一に起こらない恐れがあり、データにバラつきが出る。 In order to make the redox potential constant by electrolysis, it is necessary to control the electrolysis current while monitoring the redox potential of the solution, but the electrode for electrolysis and the electrode for measuring the redox potential are independent. In order to adjust to a constant oxidation-reduction potential by applying a potential to the electrolytic electrode and putting it in the measurement cell, a potential gradient occurs in the solution near the electrode depending on the relative position of each electrode. Shows a complicated behavior and it is difficult to control the current value.
In addition, if several independent electrodes are put into a measuring cell, the capacity of the measuring cell becomes large, the reaction may not occur uniformly, and the data varies.

特開２００１−１３１０２JP2001-13102 特開２００３−２９４６９４JP 2003-294694 A

従って、本発明の課題は、所定濃度のヨウ化カリウム酢酸緩衝溶液を用い、電気分解によりヨウ化物イオンを酸化して、その溶液の酸化還元電位を一定に制御したのち、試料を投入して、再び酸化還元電位を測定して、それらの変化量から試料中の過酢酸、過酸化水素、次亜塩素酸塩、ヨウ化物等の濃度を測定するに好適な電極を提供することを課題とする。   Therefore, an object of the present invention is to use a potassium iodide acetate buffer solution of a predetermined concentration, oxidize iodide ions by electrolysis, and after controlling the oxidation-reduction potential of the solution to be constant, put a sample, It is an object to provide an electrode suitable for measuring redox potential again and measuring the concentration of peracetic acid, hydrogen peroxide, hypochlorite, iodide, etc. in a sample from the amount of change. .

本発明者は、上記課題を解決するために、電気分解を行なう電極と酸化還元電位を測定する電極を一体化することによって、ヨウ化カリウム緩衝液を常に一定の酸化還元電位まで電気分解を行なうことができ、酸化還元電位の測定値のバラつきがなく再現性あるデータが得られることを見出し、本発明を完成した。
すなわち本発明は、電気分解を行なう電極と酸化還元電位を測定する電極を一体化した電極であって、外部管と内部管を有し、外部管側面に１対の電気分解を行なう電極と、外部管底面に酸化還元電位を測定する電極と液絡部が、いずれも被測定液に接触可能に設けられ、内部液を満たした内部管内に浸された参照電極が設けられ、前記液絡部の一端は内部液に触れ、他端が被測定液に触れるよう配設されていることを特徴とする酸化還元電位を測定する複合電極、である。 In order to solve the above problems, the inventor of the present invention integrates an electrode for performing electrolysis and an electrode for measuring the oxidation-reduction potential, so that the potassium iodide buffer is always electrolyzed to a certain oxidation-reduction potential. And the present invention has been completed by finding that reproducible data can be obtained without variation in the measured value of the oxidation-reduction potential.
That is, the present invention is an electrode in which an electrode for electrolysis and an electrode for measuring the oxidation-reduction potential are integrated, and has an outer tube and an inner tube, and an electrode for performing a pair of electrolysis on the side surface of the outer tube; An electrode for measuring the oxidation-reduction potential and a liquid junction portion are provided on the bottom surface of the outer tube so as to be in contact with the liquid to be measured, and a reference electrode immersed in the inner tube filled with the internal liquid is provided, and the liquid junction portion 1 is a composite electrode for measuring an oxidation-reduction potential, wherein one end of the electrode is disposed so as to be in contact with the internal liquid and the other end is in contact with the liquid to be measured.

また、本発明は、上記複合電極を用いて、ヨウ化カリウム緩衝液を一定の酸化還元電位まで電解酸化した溶液に、試料を投入し、酸化還元電位を測定することからなる、次亜塩素酸塩中の有効塩素濃度、又は過酢酸濃度及び／又は過酸化水素濃度の測定方法、である。   The present invention also provides hypochlorous acid, which comprises using the above composite electrode to put a sample into a solution obtained by electrolytic oxidation of a potassium iodide buffer solution to a certain redox potential and measuring the redox potential. A method for measuring an effective chlorine concentration in a salt, or a peracetic acid concentration and / or a hydrogen peroxide concentration.

本発明の電極を用いることにより、所定濃度のヨウ化カリウム酢酸緩衝溶液を、電極中の電気分解を行なう電極により酸化して、その溶液の酸化還元電位を一定に制御することができる。その結果、過酢酸、過酸化水素、次亜塩素酸塩、ヨウ化物等を含む試料を投入して再び酸化還元電位を測定し、その変化量から、バラつきがなく再現性ある分析値が得られる。   By using the electrode of the present invention, a potassium iodide acetate buffer solution having a predetermined concentration can be oxidized by the electrode that performs electrolysis in the electrode, and the oxidation-reduction potential of the solution can be controlled to be constant. As a result, a sample containing peracetic acid, hydrogen peroxide, hypochlorite, iodide, etc. is added and the oxidation-reduction potential is measured again, and a reproducible analytical value without variation is obtained from the amount of change. .

まず、図面により本発明の電極について説明する。
図１は、本発明の電気分解を行なう電極と、酸化還元電位を測定する電極を一体化した電極の各電極の配置を示す断面図である。図１において、１は、外部管であり、２は、内部管であり、３は、外部管１の側面に、被測定液に接触可能に設けられた１対の電気分解を行なう電極であり、４は、外部管１の底面に、被測定液に接触可能に設けられた酸化還元電位測定用の電極であり、５は、Ａｇ／ＡｇＣｌの参照電極であり、６は、内部液であり、７は、内部液６と測定液を連絡する液絡部であり、８は、電気分解を行なう電極３及び酸化還元電位測定用の電極４のリード線である。各リード線８は、外部管１と内部管２との間に配置されることが好ましい。 First, the electrode of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an arrangement of electrodes of an electrode in which electrolysis according to the present invention is integrated with an electrode for measuring a redox potential. In FIG. 1, 1 is an external tube, 2 is an internal tube, and 3 is a pair of electrodes that are provided on the side surface of the external tube 1 so as to be in contact with the liquid to be measured and that perform electrolysis. 4 is an electrode for measuring the redox potential provided on the bottom surface of the outer tube 1 so as to be in contact with the liquid to be measured, 5 is a reference electrode of Ag / AgCl, and 6 is an internal liquid. , 7 are liquid junctions connecting the internal liquid 6 and the measurement liquid, and 8 is a lead wire of the electrode 3 for electrolysis and the electrode 4 for redox potential measurement. Each lead wire 8 is preferably disposed between the outer tube 1 and the inner tube 2.

外部管１及び内部管２は、ガラス管が好ましいが、プラスティックのような絶縁性、耐食性を有するものであれば、その材質に制限はない。電気分解を行なう電極３には、白金、金、カーボンが用いられ、白金が好ましい。その形状は、円状が好ましいが、必ずしも真円でなくてもよく、楕円状であってもよい。また、その径は、３ｍｍ〜１０ｍｍであり、３ｍｍ未満では、電流密度が大きくなり、測定電位に影響する。また、１０ｍｍを越えると、本発明の電極の作成が困難になる。酸化還元電位測定用の電極４は、白金電極であり、その形状は円形が好ましく、直径１ｍｍ〜３ｍｍである。１ｍｍ未満では、断線の危険があり、３ｍｍを越えると、本発明の電極の作成が困難になる。   The outer tube 1 and the inner tube 2 are preferably glass tubes, but the material is not limited as long as it has insulation and corrosion resistance such as plastic. Platinum, gold, and carbon are used for the electrode 3 that performs electrolysis, and platinum is preferable. The shape is preferably a circular shape, but is not necessarily a perfect circle and may be an elliptical shape. Moreover, the diameter is 3 mm-10 mm, and if it is less than 3 mm, a current density will become large and will affect a measurement electric potential. On the other hand, if it exceeds 10 mm, it is difficult to produce the electrode of the present invention. The electrode 4 for measuring the oxidation-reduction potential is a platinum electrode, and its shape is preferably circular, and has a diameter of 1 mm to 3 mm. If it is less than 1 mm, there is a risk of disconnection, and if it exceeds 3 mm, it is difficult to produce the electrode of the present invention.

電気分解を行なう電極３と酸化還元電位測定用の電極４との距離が近すぎると、溶液を電気分解するとき、負荷する電位による電極近傍の溶液に電位勾配生じ、そのため酸化還元電位に影響を与え、溶液を一定の酸化還元電位に調整することが困難である。従って、電気分解を行なう電極３と酸化還元電位測定用の電極４との垂直距離は、４ｍｍ〜１５ｍｍである。４ｍｍ未満であると、酸化還元電位に影響を与え、１５ｍｍを越えると、電気分解を行なう電極３が、測定液に浸らなくなる。   If the distance between the electrode 3 for performing electrolysis and the electrode 4 for measuring the redox potential is too short, when the solution is electrolyzed, a potential gradient is generated in the solution in the vicinity of the electrode due to the applied potential, so that the redox potential is affected. Given, it is difficult to adjust the solution to a constant redox potential. Therefore, the vertical distance between the electrode 3 for performing electrolysis and the electrode 4 for measuring redox potential is 4 mm to 15 mm. If it is less than 4 mm, the oxidation-reduction potential is affected, and if it exceeds 15 mm, the electrode 3 that performs electrolysis is not immersed in the measurement liquid.

内部液６は、水に溶解する安定な塩化物の水溶液であり、好ましくは、塩化カリウム又は塩化ナトリウムである。
液絡部７は、多孔質セラミックが用いられるが、それに限られるものではなく、例えば、多孔質樹脂によって形成してもよい。
なお、図１は、各電極の配置を説明するために、本発明の電極の被測定液に近い部分のみを示しているが、内部管３の上部には、内部液を補充する入り口（図示せず）を有する。 The internal liquid 6 is a stable aqueous chloride solution that dissolves in water, and is preferably potassium chloride or sodium chloride.
The liquid junction portion 7 is made of porous ceramic, but is not limited thereto, and may be formed of, for example, a porous resin.
FIG. 1 shows only the portion of the electrode of the present invention close to the liquid to be measured in order to explain the arrangement of each electrode, but the upper part of the inner tube 3 is filled with an inlet (see FIG. Not shown).

次に、本発明の電極を用いて、溶液中の過酢酸、過酸化水素、次亜塩素酸塩、ヨウ化物等の濃度を測定する方法について説明する。
まず、所定濃度のヨウ化カリウム酢酸緩衝液中を測定セルにとり、その溶液に、本発明の電極を、電気分解を行なう電極部分が浸かるよう浸し、攪拌するとともに、酸化還元電位を測定しながら、電気分解を行なう電極に電位を印加して、予め設定した一定の平衡電位Ｅ０、例えば、２６０ｍＶの電位になるまで、ヨウ化物イオンの定電流電解酸化を行なう。平衡電位Ｅ０は、測定の対象や濃度により適宜設定する。この場合、本発明の電極を用いることにより、電位のオン、オフ等で酸化還元電位の変動を受けず、設定した平衡電位まで正確に電解酸化が行われる。 Next, a method for measuring the concentration of peracetic acid, hydrogen peroxide, hypochlorite, iodide, etc. in the solution using the electrode of the present invention will be described.
First, take the potassium iodide acetate buffer solution of a predetermined concentration in a measurement cell, immerse the electrode of the present invention in the solution so that the electrode part to be electrolyzed is immersed, stir and measure the oxidation-reduction potential, A potential is applied to the electrode to be electrolyzed, and constant-current electrolytic oxidation of iodide ions is performed until a constant equilibrium potential E 0 set in advance, for example, a potential of 260 mV is reached. The equilibrium potential E 0 is appropriately set depending on the measurement target and concentration. In this case, by using the electrode of the present invention, the electrolytic oxidation is accurately performed up to the set equilibrium potential without being subjected to the fluctuation of the oxidation-reduction potential due to the on / off of the potential.

次に、得られた平衡電位Ｅ０を有する、電解酸化されたヨウ化カリウム酢酸緩衝液中に試料を添加すると、溶液の平衡電位Ｅ０が新しい平衡電位Ｅまで上昇する。この平衡電位の変化量ΔＥ（ΔＥ＝Ｅ−Ｅ０）から、予め得られた検量線を用いて、試料中の過酢酸、過酸化水素、次亜塩素酸塩、ヨウ化物等の濃度を測定することができる。この方法によれば、０．１ｍｍｏｌ／Ｌから４００ｍｍｏｌ／Ｌの広い範囲の濃度の高精度の測定が可能である。 Then, with an equilibrium potential E 0 obtained, the addition of the sample during potassium iodide acetate buffer is electrolytically oxidized, the equilibrium potential E 0 of the solution is raised to a new equilibrium potential E. From this change in equilibrium potential ΔE (ΔE = E−E 0 ), the concentration of peracetic acid, hydrogen peroxide, hypochlorite, iodide, etc. in the sample is measured using a calibration curve obtained in advance. can do. According to this method, it is possible to measure with high accuracy over a wide range of concentrations from 0.1 mmol / L to 400 mmol / L.

図５は、一定の平衡電位を有する、電解酸化されたヨウ化カリウム酢酸緩衝液中に、各種濃度の有効塩素（Available chlorine、Ａｖ．Ｃｌという）を持つ次亜塩素酸ナトリウム溶液を一定量ずつ加えて、電位をモニターしたチャートである。有効塩素を含む溶液の添加により、急激な電位の上昇があり、すぐに新たな平衡電位に達する。なお、電位測定後に塩化カリウムの水溶液を添加しても、平衡電位の変動はなく、Ｃｌ−の影響は見られない。このチャートから、ΔＥが求められる。図３に示すように、電位差の変化量を測定して酸化反応量を測定する理論式に基づいて、有効塩素濃度（ｍｏｌ／Ｌ）の対数log{Av．Cl}に対してΔＥをプロットすると、良好な直線が得られ、検量線として用いられる。 FIG. 5 shows a constant amount of sodium hypochlorite solution having various concentrations of available chlorine (available chlorine, Av. Cl) in an electrolytically oxidized potassium iodide acetate buffer having a constant equilibrium potential. In addition, it is a chart in which the potential is monitored. Due to the addition of a solution containing available chlorine, there is a sudden increase in potential and a new equilibrium potential is reached immediately. Even if an aqueous solution of potassium chloride is added after the potential measurement, the equilibrium potential does not fluctuate and the influence of Cl − is not observed. From this chart, ΔE is obtained. As shown in FIG. 3, based on a theoretical formula that measures the amount of change in potential difference to measure the amount of oxidation reaction, the logarithm log {Av. When ΔE is plotted against Cl}, a good straight line is obtained and used as a calibration curve.

以下、本発明を実施例により更に詳細に説明する。
実施例１
容積が８０ｍＬのガラス製のセルに、０．０５Ｍ酢酸緩衝水溶液（ｐＨ５．４）４０ｍＬを入れ、これにヨウ化カリウムを０．２Ｍの濃度になるように溶解させる。このようにして得られたヨウ化カリウム酢酸緩衝液を、よく攪拌しながら、本発明の図１に示す電気分解を行なう電極と酸化還元電位を測定する電極を一体化した複合電極（電気分解を行なう電極の下端と酸化還元電位を測定する電極の垂直距離が５ｍｍ）を用いて、溶液の平衡電位の目標を２６０ｍＶに設定して、平衡電位をモニターしながら定電流電解を行った。このとき、電気分解、電位の制御には、ＲＫ−ＰＯＸII（過酢酸、過酸化水素モニター、理工協産株式会社製）を用いた。この電解により得られた到達平衡電位を示すチャートを図２に示す。図２より、得られた溶液の平衡電位は一定であり、電解のための電極への電位のオン、オフにも影響されない。又この操作を１０回繰り返して行ない、到達平衡電位を測定した。その結果を表１（表１）に示す。表１から全て繰り返し操作で、電気分解が一定の平衡電位になるまで行われている。 Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
In a glass cell having a volume of 80 mL, 40 mL of 0.05 M aqueous acetate buffer solution (pH 5.4) is added, and potassium iodide is dissolved therein to a concentration of 0.2 M. The potassium iodide acetate buffer solution thus obtained is mixed well, and the electrode for electrolysis shown in FIG. 1 of the present invention and the electrode for measuring the oxidation-reduction potential are integrated (electrolysis is performed). The vertical distance between the lower end of the electrode to be measured and the electrode for measuring the oxidation-reduction potential was 5 mm), and the target of the equilibrium potential of the solution was set to 260 mV, and constant current electrolysis was performed while monitoring the equilibrium potential. At this time, RK-POXII (peracetic acid, hydrogen peroxide monitor, manufactured by Riko Co., Ltd.) was used for electrolysis and potential control. A chart showing the ultimate equilibrium potential obtained by this electrolysis is shown in FIG. From FIG. 2, the equilibrium potential of the obtained solution is constant and is not affected by on / off of the potential to the electrode for electrolysis. This operation was repeated 10 times, and the ultimate equilibrium potential was measured. The results are shown in Table 1 (Table 1). All of the operations in Table 1 are repeated until the electrolysis reaches a certain equilibrium potential.

比較例１
市販の酸化還元電極１０に、電解を行なう２本の白金線９を電極として加えた手製の電極（図３）を用いた以外は、実施例１と同様に定電流電解を行った。測定した到達平衡電位のチャートを図４に示す。平衡電位が電解用電極への電位の印加の影響を受けた。 Comparative Example 1
Constant current electrolysis was performed in the same manner as in Example 1 except that a hand-made electrode (FIG. 3) in which two platinum wires 9 to be electrolyzed were added to the commercially available redox electrode 10 was used. A chart of the measured ultimate equilibrium potential is shown in FIG. The equilibrium potential was affected by the application of potential to the electrode for electrolysis.

比較例２
電気分解を行なう電極の下端と酸化還元電位を測定する電極の垂直距離を３ｍｍにする以外は、実施例１と同様に繰り返し定電流電解を行い、到達平衡電位を測定した。その結果を表１（表１）に示す。表１から、電解ごとに到達平衡電位がバラつき、目標の２６０ｍＶになる前で電解は停止している。 Comparative Example 2
Constant current electrolysis was repeated in the same manner as in Example 1 except that the vertical distance between the lower end of the electrode for electrolysis and the electrode for measuring the redox potential was 3 mm, and the ultimate equilibrium potential was measured. The results are shown in Table 1 (Table 1). From Table 1, the ultimate equilibrium potential varies for each electrolysis, and the electrolysis is stopped before the target becomes 260 mV.

Figure 0003813606
Figure 0003813606

実施例２
実施例１により得られた、一定の平衡電位Ｅ０（２６０ｍＶ）を有する、ヨウ化カリウム酢酸緩衝液（４０ｍＬ）中に、予めヨウ素−チオ硫酸ナトリウム滴定で測定した有効塩素濃度、それぞれ２８（１）、６５（２）、１３０（３）、２６０（４）、６５０（５）、１３００ｐｐｍ（６）を含む次亜塩素酸ナトリウム溶液１ｍＬ添加して、よく攪拌しながら、本発明の図１に示す電気分解を行なう電極と酸化還元電位を測定する電極を一体化した複合電極（電気分解を行なう電極の下端と酸化還元電位を測定する電極の垂直距離が５ｍｍ）を用いて、酸化還元電位を測定し、新たな平衡電位ＥＣｌを得た。得られたチャートを図５に示す。電位差の変化量ΔＥを測定して酸化反応量を測定する理論式に基づいて、有効塩素量（ｍｏｌ／Ｌ）の対数log{Av．Cl}に対してΔＥをプロットすると、良好な直線が得られ、理論式とよく合致し、有効塩素濃度の分析に有効に利用できる。（図６）。 Example 2
The effective chlorine concentration previously measured by iodine-sodium thiosulfate titration in potassium iodide acetate buffer (40 mL) having a constant equilibrium potential E 0 (260 mV) obtained in Example 1 was 28 (1 ), 65 (2), 130 (3), 260 (4), 650 (5), 1 mL of sodium hypochlorite solution containing 1300 ppm (6), and with good stirring, FIG. Using the composite electrode (the vertical distance between the lower end of the electrode for electrolysis and the electrode for measuring the oxidation-reduction potential is 5 mm) in which the electrode for electrolysis and the electrode for measuring the oxidation-reduction potential are integrated, the oxidation-reduction potential is Measurement gave a new equilibrium potential ECl . The obtained chart is shown in FIG. Based on the theoretical formula for measuring the amount of change ΔE in the potential difference and measuring the amount of oxidation reaction, the logarithm log {Av. When ΔE is plotted against Cl}, a good straight line is obtained, which is in good agreement with the theoretical formula, and can be effectively used for analysis of effective chlorine concentration. (FIG. 6).

実施例３
実施例１と同様にして、０．２Ｍ濃度のヨウ化カリウムを含む酢酸緩衝液を酸化還元電位２９０ｍＶまで電気分解した溶液中に、予めヨウ素滴定法により測定した過酢酸及び過酸化水素濃度がそれぞれ、562と926ppm（１）、1105と1086ppm（２）、2155と3594ppm（３）、3131と5275ppm（４）、4094と6988ppm（５）、5156と8776ppm（６）、6041と10334ppm（７）、7122と12185ppm（８）の８個の溶液を、１ｍＬ加えた。加えた直後に酸化還元電位は急激に上昇し、すぐに平衡状態となる。初期電位（２９０ｍＶ）とその電位との電位差ΔＥPAAが過酢酸濃度に相当する。
つづいて、その測定溶液にモリブデン酸アンモニウム溶液を１滴加えると、さらに酸化還元電位が上昇し、いずれ定常になる。この電位を読み取ると、初期電位（２９０ｍＶ）とその電位との電位差ΔＥtotalが、過酢酸と過酸水素の合計濃度に相当する。
酸化反応量を測定する理論式に基づいて、過酢酸の濃度（ｍｏｌ／Ｌ）の対数log[PAA]に対してΔＥPAAを、過酢酸と過酸化水素の合計濃度（ｍｏｌ／Ｌ）の対数log[total]に対してΔＥtotalを、それぞれプロットすると、良好な直線が得られ（図７及び８）、理論式とよく合致し、過酢酸濃度及び過酸化水素濃度の分析に有効に利用できる。 Example 3
In the same manner as in Example 1, peracetic acid and hydrogen peroxide concentrations measured in advance by the iodometric titration method in a solution obtained by electrolyzing an acetic acid buffer containing 0.2 M potassium iodide to an oxidation-reduction potential of 290 mV were respectively obtained. , 562 and 926 ppm (1), 1105 and 1086 ppm (2), 2155 and 3594 ppm (3), 3131 and 5275 ppm (4), 4094 and 6988 ppm (5), 5156 and 8776 ppm (6), 6041 and 10334 ppm (7), 1 mL of 8 solutions of 7122 and 12185 ppm (8) was added. Immediately after the addition, the redox potential rises rapidly and immediately reaches an equilibrium state. A potential difference ΔE PAA between the initial potential (290 mV) and the potential corresponds to the peracetic acid concentration.
Subsequently, when one drop of ammonium molybdate solution is added to the measurement solution, the oxidation-reduction potential further increases and eventually becomes steady. When this potential is read, the potential difference ΔE total between the initial potential (290 mV) and the potential corresponds to the total concentration of peracetic acid and hydrogen peroxide.
Based on the theoretical formula for measuring the amount of oxidation reaction, ΔE PAA is the logarithm of logarithmic log [PAA] of the concentration of peracetic acid (mol / L), and the logarithm of the total concentration of peracetic acid and hydrogen peroxide (mol / L). When ΔE total is plotted against log [total], a good straight line is obtained (FIGS. 7 and 8), which is in good agreement with the theoretical formula and can be effectively used for analysis of peracetic acid concentration and hydrogen peroxide concentration. .

本発明の複合電極の断面図の１例である。It is an example of sectional drawing of the composite electrode of this invention. 実施例１で測定された到達平衡電位の時間変化を示す図である。FIG. 6 is a diagram showing a change over time in the ultimate equilibrium potential measured in Example 1. 比較例１で使用された、市販の酸化還元電極に電解を行なう２本の白金線を電極として加えて手製の電極の断面図である。It is sectional drawing of the electrode made by adding two platinum wires which electrolyze to the commercially available redox electrode used in the comparative example 1 as an electrode. 比較例１で測定された到達平衡電位の時間変化を示す図である。FIG. 6 is a diagram showing a change over time in the ultimate equilibrium potential measured in Comparative Example 1. 実施例２における酸化還元電位の時間変化を示すチャートである。6 is a chart showing a change over time of an oxidation-reduction potential in Example 2. 実施例２で得られた有効塩素濃度（ｍｏｌ／Ｌ）の対数と平衡電位の変化量の関係を示す図である。It is a figure which shows the relationship between the logarithm of the effective chlorine concentration (mol / L) obtained in Example 2, and the variation | change_quantity of an equilibrium potential. 実施例３で得られた過酢酸濃度（ｍｏｌ／Ｌ）の対数と過酢酸の平衡電位の変化量の関係を示す図である。It is a figure which shows the relationship between the logarithm of the peracetic acid concentration (mol / L) obtained in Example 3, and the variation | change_quantity of the equilibrium potential of peracetic acid. 実施例３で得られた過酢酸濃度と過酸化水素濃度の和（ｍｏｌ／Ｌ）の対数と合計の平衡電位の変化量の関係を示す図である。It is a figure which shows the relationship between the logarithm of the sum (mol / L) of the peracetic acid concentration obtained in Example 3, and the variation | change_quantity of a total equilibrium potential.

Claims (3)

電気分解を行なう電極と酸化還元電位を測定する電極を一体化した電極であって、外部管と内部管を有し、該外部管側面に、１対の電気分解を行なう電極と、外部管底面に酸化還元電位を測定する電極と液絡部が、いずれも被測定液に接触可能に設けられ、内部液を満たした内部管内に浸された参照電極が設けられ、前記液絡部の一端は内部液に触れ、他端が被測定液に触れるよう配設されていることを特徴とする複合電極。   An electrode in which an electrode for electrolysis and an electrode for measuring an oxidation-reduction potential are integrated, and has an outer tube and an inner tube, and a pair of electrodes for electrolysis and a bottom surface of the outer tube on the side of the outer tube The electrode for measuring the oxidation-reduction potential and the liquid junction are both provided so as to be in contact with the liquid to be measured, the reference electrode immersed in the internal tube filled with the internal liquid is provided, and one end of the liquid junction is A composite electrode, wherein the composite electrode is disposed so as to be in contact with the internal liquid and the other end in contact with the liquid to be measured. 電気分解を行なう電極の下端と酸化還元電位を測定する電極の垂直距離が４〜１５ｍｍである請求項１記載の複合電極。   The composite electrode according to claim 1, wherein the vertical distance between the lower end of the electrode for electrolysis and the electrode for measuring the oxidation-reduction potential is 4 to 15 mm. 請求項１又は２の複合電極を用いて、ヨウ化カリウム緩衝液を一定の酸化還元電位まで電解酸化した溶液に、試料を投入し、酸化還元電位を測定することからなる、次亜塩素酸塩中の有効塩素濃度、又は過酢酸濃度及び／又は過酸化水素濃度の測定方法。   A hypochlorite comprising: using a composite electrode according to claim 1 or 2; and putting a sample into a solution obtained by electrolytic oxidation of a potassium iodide buffer solution to a certain oxidation-reduction potential and measuring the oxidation-reduction potential. Of effective chlorine concentration, or peracetic acid concentration and / or hydrogen peroxide concentration in water.
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