JP2004212174A

JP2004212174A - METHOD OF pH MEASUREMENT, COMPARISON ELECTRODE, AND MULTIPLE ELECTRODE

Info

Publication number: JP2004212174A
Application number: JP2002381119A
Authority: JP
Inventors: Masaharu Yamasato; 昌春山里; Taisuke Nakano; 泰介中野; Yoshinori Yanagida; 芳紀柳田
Original assignee: DKK TOA Corp
Current assignee: DKK TOA Corp
Priority date: 2002-12-27
Filing date: 2002-12-27
Publication date: 2004-07-29

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of pH measurement for an organic solvent test liquid for providing a measurement value of fast responsivity, of stable indication, and of high reliability, and to provide a comparison electrode and a multiple elecyrode used therefor. <P>SOLUTION: This method of pH measurement for an organic solvent test liquid is provided with a first comparison electrode inner liquid storage part 10A, a second comparison electrode inner liquid storage part 10B, a first liquid junction part 12A for allowing a liquid to flow out from the storage part 10A to the storage part 10B, and a second liquid junction part 12B for allowing a liquid to flow out from the storage part 10B to the exterior. The comparison electrode is employed using a water-soluble organic acid salt solution as a second comparison electrode inner liquid 16 stored in the storage part 10B. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、有機溶媒系被検液のｐＨ測定方法、更にはこれに用いる比較電極及び複合電極に関するものである。
【０００２】
【従来の技術】
周知のように、溶液のｐＨ測定には、水素イオン選択性の感応膜を有するｐＨ測定電極が使用され、その代表的なものにガラスをｐＨ感応膜とするガラス電極がある。ｐＨを測定する場合には、上記ｐＨ測定電極を作用電極とし、この作用電極を甘こう電極や銀−塩化銀電極などの比較電極と共に、測定すべき溶液（被検液）中に浸漬する。そして、両電極間の電位差から被検液のｐＨ値が求められる。
【０００３】
図７は、一般的な、ｐＨ測定電極と比較電極とが一体的に構成されたｐＨ測定用の複合電極の概略断面を示す。複合電極３は、略円柱状形状とされ、比較電極１とｐＨ測定電極２とを有する。
【０００４】
ｐＨ測定電極２は、内部に測定電極内部液２３を収容し得る測定電極内部液収容部を画成する筒体２０を有し、その先端部に被検液に接触し得るように形成されたｐＨ感応膜たるガラス膜２２を有する。又、測定電極内部液２３に浸漬された測定電極内極２１を具備している。
【０００５】
比較電極１は、ｐＨ測定電極２を囲包して、内部に比較電極内部液１３を収容し得る比較電極内部液収容部を画成する筒体１０を有し、その側壁に筒体１０から外部への比較電極内部液１３の流通を許す液絡部（ジャンクション）１２が形成されている。図示の例では、液絡部１２は、貫通孔に液透過性のセラミックを封入したセラミック形のものである。比較電極内部液１３は、被検液に少量ずつ流出するため、適宜、補給口１５から補充する。又、比較電極内部液１３には、比較電極内極１１が浸漬されている。
【０００６】
比較電極内極１１と、測定電極内極２１とは、それぞれリード線１４、２４に電気的に接続され、これらリード線１４、２４は更に、電極端子１８、２８を介して信号処理回路を備えるｐＨ測定装置（図示せず）に電気的に接続される。
【０００７】
比較電極１は、被検液に浸漬されると、液絡部１２を通して比較電極内部液１３が少量ずつ外部に流出することで、被検液と電気的導通がとられる。これにより、比較電極１とｐＨ測定電極２との間の電位差をｐＨ測定装置の電圧計で測定することにより、ｐＨ測定電極２のガラス膜２２に発生した起電力を知ることができる。ｐＨ測定装置は、この検知した起電力をｐＨ値に変換して表示などする。
【０００８】
比較電極内部液１３としては、被検液の性質、種類によって定まる被検液との間の液間起電力が最も少ない性質等の理由から、塩化カリウム（ＫＣｌ）溶液が広く用いられている。又、液絡部１２からの比較電極内部液１３の流出量が同じである場合、比較電極内部液１３の濃度が高い程液間起電力は小さくなるため、比較電極内部液１３としては、塩化カリウムの飽和溶液又は３．３ｍｏｌ／Ｌ溶液が一般に使用される。
【０００９】
通常、ｐＨなどの測定の対象は水溶液であり、様々な分野で適用されているが、特殊な用途においては、非水溶液として有機溶媒単独又は有機溶媒と水との混合溶液がｐＨなどが測定対象となることがある。例えば、ＰＣＢの処理に用いられるイソプロピルアルコール（ＩＰＡ）のアルカリ系溶液の中和処理工程で、該溶液のｐＨを測定することが行われる。この他、油脂類の酸化度中和滴定などが行われる。
【００１０】
しかし、有機溶媒系被検液のｐＨを測定する場合に、ｐＨ測定装置の応答が遅くなると共に、指示が不安定となり、信頼性のある測定値が得られないという問題があった。
【００１１】
その一因として、比較電極１の液絡部１２が比較電極内部液の結晶によって詰まることが挙げられる。
【００１２】
そこで、従来、有機溶媒系被検液のｐＨなどの測定のために、図３に示すような、内筒１０Ａ及び外筒１０Ｂにそれぞれ内筒側液絡部１２Ａ、外筒側液絡部１２Ｂを有するダブルジャンクション形の液絡部を有する比較電極（二重管式比較電極など）が用いられることがある。図示の例では、比較電極１は、外筒１０Ｂの側壁に貫通穴１２ａが設けられ、この貫通穴１２ａが設けられた部分を含む外筒１０Ｂの側壁外周に、外筒内部液１６の薄層１２ｃを介して可変スリーブ１２ｂが嵌合されている、可変スリーブ形の液絡部１２Ｂを有する。斯かる比較電極１において、外筒１０Ｂに収容する内部液１６として被検液と同種の有機溶媒系溶液（飽和ＫＣｌ溶液）を用いることにより、有機溶媒系被検液と接する外筒側液絡部１２Ｂが比較電極内部液の結晶で詰まるのを防ぐことができる。
【００１３】
【発明が解決しようとする課題】
しかしながら、上記ダブルジャンクション形の比較電極を用いて、外筒１０Ｂに収容する内部液１６として、有機溶媒系の溶液を用いる場合、内筒１０Ａ側の内部液（飽和ＫＣｌ溶液）１３と外筒１０Ｂ側の内部液１６とが接するため、内筒側液絡部１２Ａに結晶が生じることは免れ得ず、やはり測定値の不安定さ、応答の遅さの問題を解決することはできない。
【００１４】
従って、本発明の目的は、極めて簡易な方法により、応答性が速く、指示が安定し、信頼性の高い測定値を得ることができる有機溶媒系被検液のｐＨ測定方法、これに用いる比較電極及び複合電極を提供することである。
【００１５】
【課題を解決するための手段】
上記目的は本発明に係るｐＨ測定方法、比較電極及び複合電極にて達成される。要約すれば、第１の本発明は、第１の比較電極内部液収容部と、第２の比較電極内部液収容部と、前記第１の比較電極内部液収容部から前記第２の比較電極内部液収容部への液の流出を許す第１の液絡部と、前記第２の比較電極内部液収容部から外部への液の流出を許す第２の液絡部と、を有し、前記第２の比較電極内部液収容部に収容する第２の比較電極内部液として水溶性の有機酸塩溶液を用いた比較電極を使用することを特徴とする有機溶媒系被検液のｐＨ測定方法である。
【００１６】
第２の本発明によると、第１の比較電極内部液収容部と、第２の比較電極内部液収容部と、前記第１の比較電極内部液収容部から前記第２の比較電極内部液収容部への液の流出を許す第１の液絡部と、前記第２の比較電極内部液収容部から外部への液の流出を許す第２の液絡部と、を有し、有機溶媒系被検液のｐＨ測定に用い得る比較電極であって、前記第２の比較電極内部液収容部に、第２の比較電極内部液として水溶性の有機酸塩溶液が収容されることを特徴とする比較電極が提供される。
【００１７】
第３の本発明によると、測定電極内部液を収容する測定電極と；第１の比較電極内部液収容部と、第２の比較電極内部液収容部と、前記第１の比較電極内部液収容部から前記第２の比較電極内部液収容部への液の流出を許す第１の液絡部と、前記第２の比較電極内部液収容部から外部への液の流出を許す第２の液絡部と、を有する比較電極と；を一体的に有し、有機溶媒系被検液のｐＨ測定に用い得る複合電極であって、前記第２の比較電極内部液収容部に、第２の比較電極内部液として水溶性の有機酸塩溶液が収容されることを特徴とする複合電極が提供される。
【００１８】
上記各本発明の一実施態様によると、前記第２の比較電極内部液として、蟻酸、酢酸、プロピオン酸、酪酸のアルカリ金属塩溶液を用いる。一実施態様では、前記第２の比較電極内部液の濃度は、０．１ｍｏｌ／Ｌ〜３ｍｏｌ／Ｌである。好ましい一実施態様によると、前記第１の比較電極内部液収容部に収容する第１の比較電極内部液として、前記比較電極と組み合わされて使用される測定電極の内部液と実質的に同一の溶液を用いる。一実施態様では、前記第１の比較電極内部液として、塩化カリウム溶液を用いる。好ましくは、この塩化カリウム溶液は、飽和溶液又は３．３ｍｏｌ／Ｌ溶液である。
【００１９】
上記各本発明の一実施態様によると、前記第１の比較電極内部液収容部は、前記第２の比較電極内部液収容部内に入れ子式に形成されている。
【００２０】
ここで、有機溶媒とは、固体、気体、液体（とけ合う）の溶質を溶解することのできる液体の有機化合物をいう。
【００２１】
又、有機溶媒系溶液（若しくは有機溶媒系被検液）とは、有機溶媒単独及び有機溶媒と水との混合溶液を含むものとする。
【００２２】
【発明の実施の形態】
以下、本発明に係る有機溶媒系被検液のｐＨ測定方法、比較電極及び複合電極を図面に則して更に詳しく説明する。
【００２３】
上述のように、比較電極の液絡部にて発生する液間起電力などの影響により指示が不安定となるのを防止するために、従来、溶液のｐＨ測定に用いる比較電極の内部液としては、塩化カリウム（ＫＣｌ）の飽和若しくは３．３ｍｏｌ／Ｌ溶液が広く用いられている。即ち、比較電極の内部液は濃度が高い程、測定値を安定化することができる。塩化カリウム溶液は、どのような液に対しても液間起電力がほとんど生じないことから、比較電極内部液として最も好ましく使用されている。
【００２４】
そして、斯かる比較電極と組み合わされて使用されるｐＨ測定電極の内部液としても、従来一般に、塩化カリウムの飽和溶液又は３．３ｍｏｌ／Ｌ溶液を用い、内部発生電位を比較電極１とｐＨ測定電極２とで同じにして、ｐＨ測定装置での検出信号の処理を容易ならしめている。
【００２５】
一方、上述のように、有機溶媒系被検液のｐＨ測定する場合に、例えば、単一の液絡部を有する比較電極の内部液として、或いは内筒と外筒を具備するダブルジャンクション形の液絡部を有する比較電極の外筒側の内部液として、従来一般に用いられている塩化カリウムの飽和溶液又は３．３ｍｏｌ／Ｌ溶液を用いると、比較電極内部液と有機溶媒中とでその溶質の溶解度が相違することから、液絡部から流出してきた比較電極内部液が有機溶媒と接したときに、液絡部で直ちに結晶が析出し、液絡部が内部液の結晶によって詰まる。又、上述のように、ダブルジャンクション形の液絡部を有する比較電極を用いて、外筒側の内部液として被検液と同種の有機溶媒の飽和ＫＣｌ溶液を用いた場合においても、内筒側液絡部に結晶が生じる。これにより、指示値の応答性、安定性、信頼性が低下する。
【００２６】
このように、有機溶媒系被検液のｐＨ測定においては、比較電極内部液をより高濃度として測定値の安定化する一方、液絡部での結晶の析出を防止するという、相反する要求を同時に満たすことが必要である。
【００２７】
そこで、本発明の有機溶媒系被検液のｐＨ測定方法では、有機溶媒系被検液と接する比較電極の液絡部に結晶が析出しないようにするために、ダブルジャンクション形の液絡部を具備する比較電極を用い、有機溶媒と接する側の内部液（外筒側の内部液）に、有機溶媒に対する溶解度が比較的高く、液絡部で結晶が析出しない、水溶性の有機酸塩溶液を用いる。
【００２８】
本発明にて使用し得る水溶性の有機酸系塩には、カルボン酸、芳香族カルボン酸の塩が含まれる。水に対する溶解度の点で、実用上カルボン酸の塩、特に、Ｃ１〜Ｃ４カルボン酸、即ち、蟻酸、酢酸、プロピオン酸、酪酸のアルカリ金属塩が好ましい。
【００２９】
有機酸塩溶液の濃度は、０．１ｍｏｌ／Ｌ〜３ｍｏｌ／Ｌが好適である。この範囲よりも低濃度であると、液絡部での抵抗が増大してノイズを受け易くなる虞がある。又、この範囲よりも高濃度であると、例えば、後述のように内筒側の内部液として例えばＫＣｌ水溶液を用いた場合に、内筒側の液絡部でＫＣｌの析出が生じる虞がある。より好ましくは、１〜３ｍｏｌ／Ｌである。
【００３０】
一般に、液絡部からの比較電極内部液の流出量は極めて僅か（通常、１ｍＬ／日以下）であり、液絡部を介して被検液に流出した比較電極内部液が拡散希釈されることから、比較電極を静置状態の被検液に、極端に長時間浸漬するようなことがなければ、外筒側の内部液は、上記範囲内の濃度で実用上何ら問題ない。
【００３１】
一方、ダブルジャンクション形の液絡部を具備する比較電極において、有機溶媒系被検液とは直接接触しない側の内部液（内筒側の内部液）としては、当業者には周知のｐＨ測定技術における一般的な理論、実践を背景に、適当な電解質溶液を適当な濃度にて用いることができる。好ましくは、アルカリ金属のハロゲン化物であり、上述のように、最も好ましくは塩化カリウム（ＫＣｌ）溶液である。又、上述のように、この塩化カリウム溶液は、飽和溶液又は３．３ｍｏｌ／Ｌ溶液とするのが一般的であり、又最も好ましい。
【００３２】
又、内筒側の内部液には、当該比較電極が組み合わされて使用されるｐＨ測定電極の内部液と実質的に同一のものを用いるのが望ましい。
【００３３】
上述の構成とすることにより、液間起電力の影響等が測定値を不安定とすることのない高濃度の比較電極内部液を用いながら、比較電極の有機溶媒系被検液と接する液絡部が結晶で詰まることを防止することができる。又、従来、ダブルジャンクション形の液絡部を具備する比較電極を用いて外筒側の内部液に有機溶媒系被検液と同種の有機溶媒系溶液とした場合に生じていた内筒側の液絡部の内筒側の内部液の結晶による詰まりを防止することもできる。従って、有機溶媒系被検液のｐＨ測定における複合電極３の応答性、安定性の低下といった問題を回避することができる。
【００３４】
又、比較電極の内筒側の内部液としてｐＨ測定電極の内部液と実質的に同一の溶液を用いることで、比較電極１とｐＨ測定電極との内部発生電位が同じになり、ｐＨ測定装置による検出信号の処理を容易にすることができる。
【００３５】
以下、本発明に従う有機溶媒系被検液のｐＨ測定方法、比較電極及び複合電極を、具体的な実施例を通して更に説明する。以下の実施例は、本発明のより良い理解のために供されるものであって、本発明を限定する意図はない。又、以下の実施例における操作、用いられる器具、試薬自体は、特に言及しない場合、斯界にて一般的なものである。
【００３６】
実施例１
本実施例では、本発明に従い、有機溶媒系被検液としてイソプロピルアルコール（ＩＰＡ）のアルカリ系溶液のｐＨ測定を行った。
【００３７】
図２は、本実施例で用いたｐＨ測定系の概略構成を示す。ｐＨの測定系は、ガラス電極とされるｐＨ測定電極（東亜ディーケーケー（株）製、型番ＨＧＳ−２００５）２と、塩化カリウム溶液に接触させた銀−塩化銀電極とされる比較電極（東亜ディーケーケー（株）製、型番ＨＳ−３０５ＤＳ）１と、電圧計５０を具備するｐＨ測定装置（東亜ディーケーケー（株）製、型番ＨＭ−６０Ｇ）とを有する。そして、比較電極１及びｐＨ測定電極２は、容器１００に収容した被検液Ｓに浸漬される。
【００３８】
ｐＨ測定電極２は、略円柱状形状であり、測定電極内部液２３を収容し得る測定電極内部液収容部を画成する筒体２０を有し、その先端にｐＨ感応膜たるガラス膜２２が設けられている。筒体２０内の測定電極内部液２３内には、測定電極内極２１が浸漬されている。測定電極内極２１は、リード線２４と電気的に接続され、更にリード線は筒体２０の外部に導かれて、電極端子２８を介してｐＨ測定装置の電圧計５０に電気的に接続されている。本実施例では、測定電極内部液２３は、３．３ｍｏｌ／ＬのＫＣｌ水溶液である。
【００３９】
又、比較電極１としては、ダブルジャンクション形の液絡部を有するものを用いた。図３は本実施例にて用いた比較電極の要部概略断面をより詳しく示す。斯かる比較電極１は、略円柱形状とされ、同軸的に、第１の比較電極内部液収容部としての内筒１０Ａと、第２の比較電極内部液収容部としての外筒１０Ｂとが、入れ子式に形成されている。内筒１０Ａ、外筒１０Ｂには、それぞれ外部から内部液を充填し得るように補充口（図示せず）が設けられている。
【００４０】
内筒１０Ａ内には、第１の比較電極内部液たる内筒内部液１３が収容され、これに比較電極内極（銀−塩化銀電極）が浸漬されている。又、内筒１０Ａの先端には、第１の液絡部としてのセラミック形の内筒側液絡部１２Ａが設けられている。又、外筒１０Ｂ内には、第２の比較電極内部液たる外筒内部液１６が収容され、その先端近傍の側壁には、貫通孔１２ａが設けられている。この貫通孔１２ａが設けられた部分を含む外筒１０Ｂの外周壁を取り巻くように、外筒内部液１６の薄層１２ｃを介して可変スリーブ１２ｂが嵌合され、第２の液絡部としての可変スリーブ形の外筒側液絡部１２Ｂが形成されている。可変スリーブ１２ｂは、貫通孔１２ａからの液流出量を所定量以下にする使用状態における閉鎖位置と、貫通孔１２ｂを開放する開位置との間で、図中矢印にて示す方向に移動可能である。
【００４１】
このようなダブルジャンクション形の液絡部により、比較電極１を被検液Ｓに浸漬したときに、内筒側液絡部１２Ａを介して内筒１０Ａから外筒１０Ａへと内筒内部液１３が少量ずつ流出し、又外筒側液絡部１２Ｂを介して外筒１０Ｂから外部へと外筒内部液１６が少量ずつ流出して、比較電極１は被検液Ｓと電気的な導通がとられる。
【００４２】
本実施例では、水溶性の有機酸塩溶液として、１ｍｏｌ／Ｌの酢酸リチウム（ＣＨ_３ＣＯＯＬｉ）水溶液を、外筒内部液１６に用いた。又、内筒内部液１３としては、従来一般に用いられている３．３ｍｏｌ／ＬのＫＣｌ水溶液（東亜ディーケーケー（株）製、ＫＣＬ−３．３Ｎ）を用いた。
【００４３】
そして、比較電極１とｐＨ測定電極２とを、有機溶媒系被検液としてＮａＯＨのイソプロピルアルコール溶液に浸漬すると同時にｐＨ測定を開始し、その後のｐＨ指示を記録した。尚、ｐＨ測定中、被検液は磁気攪拌子により適度に攪拌した。
【００４４】
比較例として、比較電極１の内筒内部液１３及び外筒内部液１６に、従来一般に用いられている３．３ｍｏｌ／ＬのＫＣｌ水溶液を用いた場合についても、同様にｐＨ指示を記録した。結果を図１に示す。
【００４５】
図１から分かるように、外筒内部液１６として３．３ｍｏｌ／ＬのＫＣｌ水溶液を用いた比較例では、測定開始からｐＨ指示が徐々に上昇し続け、測定時間１８分を超えてもなお安定値に達し得なかった。
【００４６】
これに対して外筒内部液１６として１ｍｏｌ／Ｌの酢酸リチウム水溶液を用いた本実施例では、測定開始後直ちにｐＨ指示は安定値に達し、その後この指示を維持した。
【００４７】
測定後に本実施例の比較電極１における内筒側液絡部１２Ａ、外筒側液絡部１２Ｂを観察したが、いずれにおいても結晶は見当たらなかった。その後、その比較電極１を用いて再びｐＨ測定を行ったが、ｐＨ指示の再現性、安定性は良好であった。
【００４８】
尚、本実施例では、外筒側液絡部１２Ｂが可変スリーブ形であるとして説明したが、本発明はこれに限定されるものではない。本発明によれば、液絡部の詰まりは発生せず、内部液の流出が確保されるので、液絡部の構造は問わない。例えば、図４に示すように、外筒側液絡部１２Ｂはセラミック形であってもよい。その他、液絡部としては、ファイバ形、ピンホール形、固定スリーブ形など、斯界にて周知のものを任意に利用し得る。ファイバ形の液絡部は、液絡部を毛細管状に形成したもので、ピンホール形の液絡部は、液絡部を微小な貫通孔として形成したものである。又、固定スリーブは、上記可変スリーブを移動不可能にしたものに相当する。本実施例の比較電極１の内筒側液絡部１２Ａについても、セラミック形に限られるものではない。
【００４９】
以上、本発明に従って、極めて簡易な方法によって、有機溶媒系被検液のｐＨ測定において安定した指示を得ることができる。
【００５０】
実施例２
次に、本発明の他の実施例について説明する。本実施例では、本発明は、ｐＨ測定用の複合電極に具現化される。
【００５１】
図５は、本発明を適用し得る複合電極３の一実施例の要部概略断面を示す。尚、比較電極１とｐＨ測定電極２とは、一体的に構成されている以外は、基本的に上記実施例１のものと同じ作用を成す。従って、同じ機能を有する要素には同じ符号を付し、詳しい説明は省略する。
【００５２】
図示するように、複合電極３は、ガラス電極とされるｐＨ測定電極２と、ダブルジャンクション形の液絡部を具備する比較電極１とが一体的に構成されて成る。ここでは、比較電極１における第２の液絡部たる外筒側液絡部１２Ｂは、可変スリーブ形とされる。又、本実施例では、複合電極３は、略円柱形状とされ、同軸的に、ｐＨ測定電極２、比較電極の内筒１０Ａ、比較電極１の外筒１０Ｂが、ほぼ内側からこの順に形成されている。ｐＨ測定電極２のガラス膜２２は、複合電極３の先端に、被検液と接し得るように形成されている。
【００５３】
上記同様、外筒側液絡部１２Ｂは可変スリーブ形に限らず、例えば、図６に示すようにセラミック形であってもよい。その他、液絡部としては、ファイバ形、ピンホール形、固定スリーブ形など、斯界にて周知のものを任意に利用し得る。内筒側液絡部１２Ａについても、セラミック形に限られるものではない。
【００５４】
尚、当業者には容易に理解されるように、複合電極３は更に、温度検知手段など一体に有していてもよい。
【００５５】
本発明に従い、複合電極３の外筒内部液１６として、測定対象の有機溶媒系被検液と接触したときに結晶を析出しない、水溶性の有機酸塩溶液を用いる。これにより、液間起電力の影響等が測定値を不安定とすることのない高濃度の比較電極内部液を用いながら、外筒側液絡部１２Ｂが外筒内部液１６の結晶で詰まることを防止することができる。又、従来、外筒内部液１６に有機溶媒系被検液を用いる場合に生じていた、内筒側液絡部１２Ａにおける結晶による詰まりを防止することもできる。従って、有機溶媒系被検液のｐＨ測定における複合電極３の応答性、安定性の低下といった問題を回避することができる。
【００５６】
又、内筒内部液１３として、ｐＨ測定電極２の内部液２３と実質的に同一の溶液を用いる。これによって、比較電極１と測定電極２とで内部発生電位が同じになり、ｐＨ測定装置での検出信号の処理が容易となる。
【００５７】
以上、本発明を比較電極１とｐＨ測定電極２とが一体的に構成された複合電極３に適用することによって、有機溶媒系被検液のｐＨ測定において、１つのセンサ部材を被検液に適用すれば測定が可能であるという複合電極の利便性を生かしつつ、極めて簡易な方法によって、応答性よく、安定した指示を得ることができる。
【００５８】
【発明の効果】
以上説明したように、本発明よれば、有機溶媒系被検液のｐＨ測定方法は、第１の比較電極内部液収容部と、第２の比較電極内部液収容部と、第１の比較電極内部液収容部から第２の比較電極内部液収容部への液の流出を許す第１の液絡部と、第２の比較電極内部液収容部内から外部への液の流出を許す第２の液絡部と、を有し、第２の比較電極内部液収容部に収容する第２の比較電極内部液として、水溶性の有機酸塩溶液を用いた比較電極を使用する構成とされるので、極めて簡易な方法により、応答性が速く、指示が安定し、信頼性の高い測定値を得ることができる。又、本発明によれば、斯かる本発明の方法を具現化する比較電極及び複合電極が提供され、それぞれ上記本発明のｐＨ測定方法に対応する作用効果を得ることができる。
【図面の簡単な説明】
【図１】有機溶媒系被検液のｐＨ測定値の安定性を示すグラフ図である。
【図２】本発明を適用し得るｐＨ測定系の概略構成図である。
【図３】本発明を適用し得る比較電極の一例の要部概略断面図である。
【図４】本発明を適用し得る比較電極の他の例の要部概略断面図である。
【図５】本発明を適用し得る複合電極の一例の要部概略断面図である。
【図６】本発明を適用し得る複合電極の他の例の要部概略断面図である。
【図７】従来のｐＨ測定用複合電極の一例の要部概略断面図である。
【符号の説明】
１比較電極
２ｐＨ測定電極（測定電極）
３複合電極
１０比較電極内部液収容部
１０Ａ内筒（第１の比較電極内部液収容部）
１０Ｂ外筒（第２の比較電極内部液収容部）
１１比較電極内極
１２液絡部
１２ｂ可変スリーブ
１２Ａ内筒側液絡部（第１の液絡部）
１２Ｂ外筒側液絡部（第２の液絡部）
１３比較電極内部液、内筒内部液
１６比較電極内部液、外筒内部液
２０測定電極内部液収容部
２１測定電極内極
２２ガラス膜（感応膜）
２３測定電極内部液[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for measuring the pH of an organic solvent-based test liquid, and further to a comparative electrode and a composite electrode used for the method.
[0002]
[Prior art]
As is well known, for measuring the pH of a solution, a pH measuring electrode having a hydrogen ion-selective sensitive membrane is used, and a typical example thereof is a glass electrode using glass as a pH sensitive membrane. When measuring pH, the above-mentioned pH measuring electrode is used as a working electrode, and this working electrode is immersed in a solution (test liquid) to be measured together with a comparative electrode such as a ginger electrode or a silver-silver chloride electrode. Then, the pH value of the test solution is determined from the potential difference between the two electrodes.
[0003]
FIG. 7 shows a schematic cross section of a general composite electrode for pH measurement in which a pH measurement electrode and a reference electrode are integrally formed. The composite electrode 3 has a substantially columnar shape, and includes a comparison electrode 1 and a pH measurement electrode 2.
[0004]
The pH measurement electrode 2 has a cylindrical body 20 that defines a measurement electrode internal liquid storage portion capable of storing the measurement electrode internal liquid 23 therein, and is formed at the tip thereof so as to be in contact with the test liquid. It has a glass film 22 as a pH-sensitive film. In addition, a measurement electrode inner electrode 21 immersed in the measurement electrode inner liquid 23 is provided.
[0005]
The comparative electrode 1 has a cylindrical body 10 surrounding the pH measuring electrode 2 and defining a comparative electrode internal liquid storage portion capable of storing the comparative electrode internal liquid 13 therein. A liquid junction (junction) 12 is formed to allow the reference electrode internal liquid 13 to flow to the outside. In the illustrated example, the liquid junction 12 is of a ceramic type in which a liquid-permeable ceramic is sealed in a through hole. The reference electrode internal solution 13 is replenished from the replenishing port 15 as appropriate because it flows out little by little into the test solution. The reference electrode inner electrode 11 is immersed in the reference electrode inner liquid 13.
[0006]
The reference electrode inner electrode 11 and the measurement electrode inner electrode 21 are electrically connected to lead wires 14 and 24, respectively, and these lead wires 14 and 24 further include a signal processing circuit via electrode terminals 18 and 28. It is electrically connected to a pH measuring device (not shown).
[0007]
When the reference electrode 1 is immersed in the test liquid, the reference electrode internal liquid 13 flows out little by little through the liquid junction 12 to be electrically connected to the test liquid. Thus, the electromotive force generated in the glass film 22 of the pH measurement electrode 2 can be known by measuring the potential difference between the reference electrode 1 and the pH measurement electrode 2 with the voltmeter of the pH measurement device. The pH measuring device converts the detected electromotive force into a pH value and displays it.
[0008]
As the reference electrode internal liquid 13, a potassium chloride (KCl) solution is widely used because of the property of the test liquid and the property of the lowest inter-liquid electromotive force between the test liquid and the test liquid determined by the type. Further, when the amount of the reference electrode internal liquid 13 flowing out from the liquid junction 12 is the same, the higher the concentration of the reference electrode internal liquid 13 is, the smaller the inter-liquid electromotive force is. A saturated or 3.3 mol / L solution of potassium is generally used.
[0009]
Usually, the measurement target of pH and the like is an aqueous solution, which is applied in various fields.However, in special applications, a non-aqueous solution such as an organic solvent alone or a mixed solution of an organic solvent and water is used as a measurement target It may be. For example, in a neutralization treatment step of an alkaline solution of isopropyl alcohol (IPA) used for treating PCB, the pH of the solution is measured. In addition, titration for neutralization of the degree of oxidation of fats and oils is performed.
[0010]
However, when measuring the pH of an organic solvent-based test solution, there has been a problem that the response of the pH measuring device becomes slow, the indication becomes unstable, and a reliable measured value cannot be obtained.
[0011]
One reason for this is that the liquid junction 12 of the comparative electrode 1 is clogged with crystals of the liquid inside the comparative electrode.
[0012]
Conventionally, as shown in FIG. 3, an inner cylinder side liquid junction 12A and an outer cylinder side liquid junction 12B are attached to an inner cylinder 10A and an outer cylinder 10B, respectively, as shown in FIG. In some cases, a reference electrode having a double junction type liquid junction having a double junction type (such as a double tube type reference electrode) may be used. In the illustrated example, the comparative electrode 1 is provided with a through hole 12a in the side wall of the outer cylinder 10B, and a thin layer of the outer cylinder internal liquid 16 is formed on the outer periphery of the side wall of the outer cylinder 10B including the portion where the through hole 12a is provided. It has a variable sleeve type liquid junction part 12B in which a variable sleeve 12b is fitted via 12c. In the comparative electrode 1, by using an organic solvent-based solution (saturated KCl solution) of the same kind as the test liquid as the internal liquid 16 contained in the outer cylinder 10B, the outer-tube-side liquid junction in contact with the organic solvent-based test liquid is used. The portion 12B can be prevented from being clogged with crystals of the liquid inside the comparison electrode.
[0013]
[Problems to be solved by the invention]
However, when an organic solvent-based solution is used as the internal liquid 16 housed in the outer cylinder 10B using the double junction type comparison electrode, the internal liquid (saturated KCl solution) 13 on the inner cylinder 10A side and the outer cylinder 10B Since the inner liquid 16 is in contact with the inner liquid 16, it is unavoidable that crystals are formed in the inner cylinder side liquid junction 12 A, and the problems of instability of measured values and slow response cannot be solved.
[0014]
Accordingly, an object of the present invention is to provide a method for measuring the pH of an organic solvent-based test liquid capable of obtaining a highly responsive, fast-reading, and reliable measurement value by an extremely simple method, and a comparative method used for the method. It is to provide an electrode and a composite electrode.
[0015]
[Means for Solving the Problems]
The above object is achieved by a pH measuring method, a comparative electrode and a composite electrode according to the present invention. In summary, the first aspect of the present invention provides a first comparative electrode internal liquid storage section, a second comparative electrode internal liquid storage section, and a first comparative electrode internal liquid storage section to the second comparative electrode. A first liquid junction that allows the liquid to flow out to the internal liquid storage part, and a second liquid junction that allows the liquid to flow out of the second comparison electrode internal liquid storage part to the outside, PH measurement of an organic solvent-based test liquid, wherein a reference electrode using a water-soluble organic acid salt solution is used as the second reference electrode internal liquid contained in the second reference electrode internal liquid storage section. Is the way.
[0016]
According to the second aspect of the present invention, the first comparative electrode internal liquid storage section, the second comparative electrode internal liquid storage section, and the second comparative electrode internal liquid storage section from the first comparative electrode internal liquid storage section. An organic solvent system, comprising: a first liquid junction that allows liquid to flow out of the liquid storage portion; and a second liquid junction that allows liquid to flow out of the second comparison electrode internal liquid storage portion to the outside. A comparison electrode that can be used for pH measurement of a test liquid, wherein the second comparison electrode internal liquid storage section contains a water-soluble organic acid salt solution as a second comparison electrode internal liquid. A comparison electrode is provided.
[0017]
According to a third aspect of the present invention, a measurement electrode for storing a liquid inside the measurement electrode; a first comparison electrode internal liquid storage part, a second comparison electrode internal liquid storage part, and the first comparison electrode internal liquid storage. A first liquid junction for allowing the liquid to flow from the portion to the second reference electrode internal liquid storage, and a second liquid for allowing the liquid to flow from the second comparison electrode internal liquid storage to the outside And a comparison electrode having a entangled portion; and a composite electrode that can be used for measuring the pH of the organic solvent-based test liquid, wherein the second reference electrode internal liquid storage section has a second electrode. A composite electrode is provided, wherein a water-soluble organic acid salt solution is contained as a reference electrode internal liquid.
[0018]
According to one embodiment of the present invention, an alkali metal salt solution of formic acid, acetic acid, propionic acid, and butyric acid is used as the internal liquid of the second comparative electrode. In one embodiment, the concentration of the second comparative electrode internal liquid is 0.1 mol / L to 3 mol / L. According to a preferred embodiment, the first reference electrode internal liquid contained in the first reference electrode internal liquid storage portion is substantially the same as the internal liquid of the measurement electrode used in combination with the reference electrode. Use solution. In one embodiment, a potassium chloride solution is used as the first reference electrode internal liquid. Preferably, the potassium chloride solution is a saturated solution or a 3.3 mol / L solution.
[0019]
According to one embodiment of the present invention, the first comparative electrode internal liquid storage section is nested in the second comparison electrode internal liquid storage section.
[0020]
Here, the organic solvent refers to a liquid organic compound that can dissolve a solid, gas, or liquid (melt) solute.
[0021]
The organic solvent-based solution (or the organic solvent-based test liquid) includes an organic solvent alone or a mixed solution of an organic solvent and water.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the method for measuring the pH of an organic solvent-based test liquid, a comparative electrode, and a composite electrode according to the present invention will be described in more detail with reference to the drawings.
[0023]
As described above, in order to prevent the indication from becoming unstable due to the effect of the liquid electromotive force generated at the liquid junction of the comparative electrode, conventionally, the internal liquid of the comparative electrode used for pH measurement of the solution is used. Is widely used as a saturated or 3.3 mol / L solution of potassium chloride (KCl). That is, the higher the concentration of the liquid inside the comparative electrode, the more stable the measured value. The potassium chloride solution is most preferably used as a reference electrode internal solution because almost no liquid electromotive force is generated for any solution.
[0024]
Conventionally, a saturated solution of potassium chloride or a 3.3 mol / L solution of potassium chloride is generally used as an internal solution of the pH measuring electrode used in combination with the comparative electrode, and the internally generated potential is measured with the comparative electrode 1 and the pH measurement. In the same manner as the electrode 2, the processing of the detection signal in the pH measuring device is facilitated.
[0025]
On the other hand, as described above, when measuring the pH of the organic solvent-based test solution, for example, as the internal solution of a comparative electrode having a single liquid junction, or a double junction type having an inner tube and an outer tube When a saturated solution or a 3.3 mol / L solution of potassium chloride, which is conventionally used, is used as the internal liquid on the outer cylinder side of the reference electrode having a liquid junction, the solute in the reference electrode internal liquid and the organic solvent is used. When the liquid inside the comparative electrode flowing out of the liquid junction comes into contact with the organic solvent, crystals are immediately precipitated at the liquid junction, and the liquid junction is clogged with crystals of the internal liquid. In addition, as described above, even when a saturated KCl solution of the same kind of organic solvent as the test liquid is used as the internal liquid on the outer cylinder side using the comparative electrode having the double junction type liquid junction, as described above, Crystals form at the side junction. As a result, the responsiveness, stability, and reliability of the indicated value decrease.
[0026]
As described above, in the pH measurement of the organic solvent-based test solution, there is a conflicting demand that the concentration of the liquid in the reference electrode be made higher to stabilize the measured value while preventing precipitation of crystals at the liquid junction. It is necessary to meet at the same time.
[0027]
Therefore, in the method for measuring the pH of an organic solvent-based test liquid of the present invention, a double junction type liquid junction is formed in order to prevent crystals from being deposited at a liquid junction of a comparative electrode in contact with the organic solvent-based test liquid. A water-soluble organic acid salt solution that has a relatively high solubility in an organic solvent and does not precipitate crystals at a liquid junction in an internal liquid on the side in contact with the organic solvent (an internal liquid on the outer cylinder side) using a comparative electrode provided. Is used.
[0028]
Water-soluble organic acid-based salts that can be used in the present invention include salts of carboxylic acids and aromatic carboxylic acids. From the viewpoint of solubility in water, salts of carboxylic acids, particularly, C1 to C4 carboxylic acids, that is, alkali metal salts of formic acid, acetic acid, propionic acid, and butyric acid are preferred in practice.
[0029]
The concentration of the organic acid salt solution is preferably from 0.1 mol / L to 3 mol / L. If the concentration is lower than this range, there is a possibility that the resistance at the liquid junction increases and noise is easily received. If the concentration is higher than this range, for example, when KCl aqueous solution is used as the internal liquid on the inner cylinder side as described later, KCl may be precipitated at the liquid junction on the inner cylinder side. . More preferably, it is 1-3 mol / L.
[0030]
In general, the amount of the reference electrode internal solution flowing out of the liquid junction is extremely small (usually 1 mL / day or less), and the reference electrode internal liquid flowing out to the test liquid through the liquid junction is diffused and diluted. Therefore, unless the reference electrode is immersed in the test liquid in the stationary state for an extremely long time, the internal liquid on the outer cylinder side has no practical problem at a concentration within the above range.
[0031]
On the other hand, in the comparative electrode having a double junction type liquid junction, the internal solution on the side that is not in direct contact with the organic solvent-based test solution (the internal solution on the inner cylinder side) is a pH measurement known to those skilled in the art. Against the background of general theory and practice in technology, appropriate electrolyte solutions can be used at appropriate concentrations. Preferably, it is a halide of an alkali metal, and, as mentioned above, most preferably a potassium chloride (KCl) solution. As described above, this potassium chloride solution is generally and most preferably a saturated solution or a 3.3 mol / L solution.
[0032]
Further, it is desirable that the inner liquid on the inner cylinder side be substantially the same as the inner liquid of the pH measuring electrode used in combination with the comparative electrode.
[0033]
With the above configuration, the liquid junction in contact with the organic solvent-based test liquid of the reference electrode can be obtained while using a high-concentration internal liquid of the reference electrode, which does not make the measured value unstable due to the effect of the liquid electromotive force. The portion can be prevented from being clogged with crystals. Also, conventionally, the inner cylinder side which has been generated when the same solution of the organic solvent test liquid as the organic solvent test liquid is used for the inner liquid on the outer cylinder side using a comparative electrode having a double junction type liquid junction. It is also possible to prevent the internal liquid on the inner cylinder side of the liquid junction from being clogged with crystals. Therefore, it is possible to avoid problems such as a decrease in responsiveness and stability of the composite electrode 3 in pH measurement of an organic solvent-based test liquid.
[0034]
Further, by using a solution that is substantially the same as the internal solution of the pH measuring electrode as the internal solution on the inner cylinder side of the comparative electrode, the internally generated potential of the comparative electrode 1 and the pH measuring electrode becomes the same, and the pH measuring device Can easily process the detection signal.
[0035]
Hereinafter, the method for measuring the pH of an organic solvent-based test solution, a comparative electrode, and a composite electrode according to the present invention will be further described through specific examples. The following examples are provided for a better understanding of the present invention and are not intended to limit the present invention. Unless otherwise specified, the operations, instruments and reagents used in the following examples are common in the art.
[0036]
Example 1
In this example, according to the present invention, the pH of an alkaline solution of isopropyl alcohol (IPA) was measured as an organic solvent-based test solution.
[0037]
FIG. 2 shows a schematic configuration of the pH measurement system used in this example. The pH measurement system includes a pH measurement electrode (available from Toa DKK Ltd., Model No. HGS-2005) 2, which is a glass electrode, and a comparison electrode (available from Toa DKK, Inc.) which is a silver-silver chloride electrode brought into contact with a potassium chloride solution. (Model: HS-305DS, manufactured by K.K.) and a pH measuring device (Model: HM-60G, manufactured by Toa DKK Ltd.) equipped with a voltmeter 50. Then, the comparative electrode 1 and the pH measurement electrode 2 are immersed in the test liquid S stored in the container 100.
[0038]
The pH measurement electrode 2 has a substantially cylindrical shape, has a cylindrical body 20 that defines a measurement electrode internal liquid storage section capable of storing the measurement electrode internal liquid 23, and a glass film 22 serving as a pH sensitive film is provided at the tip thereof. Is provided. The measurement electrode inner electrode 21 is immersed in the measurement electrode inner liquid 23 in the cylinder 20. The measurement electrode inner electrode 21 is electrically connected to a lead wire 24, and further, the lead wire is led to the outside of the cylindrical body 20, and is electrically connected to a voltmeter 50 of a pH measurement device via an electrode terminal 28. ing. In this embodiment, the measurement electrode internal liquid 23 is a 3.3 mol / L KCl aqueous solution.
[0039]
As the comparative electrode 1, an electrode having a double junction type liquid junction was used. FIG. 3 shows a schematic cross section of a main part of a comparative electrode used in this example in more detail. Such a comparative electrode 1 has a substantially cylindrical shape, and coaxially includes an inner cylinder 10A as a first comparative electrode internal liquid storage unit and an outer cylinder 10B as a second comparison electrode internal liquid storage unit. It is nested. Each of the inner cylinder 10A and the outer cylinder 10B is provided with a replenishing port (not shown) so that the internal liquid can be filled from the outside.
[0040]
In the inner cylinder 10A, an inner cylinder internal liquid 13 which is a first comparative electrode internal liquid is accommodated, and a comparative electrode inner electrode (silver-silver chloride electrode) is immersed therein. At the tip of the inner cylinder 10A, a ceramic inner cylinder-side liquid junction 12A is provided as a first liquid junction. The outer cylinder 10B contains an outer cylinder internal liquid 16 as a second comparison electrode internal liquid, and a through hole 12a is provided in a side wall near the distal end thereof. The variable sleeve 12b is fitted through the thin layer 12c of the liquid 16 inside the outer cylinder so as to surround the outer peripheral wall of the outer cylinder 10B including the portion provided with the through hole 12a, and serves as a second liquid junction. A variable sleeve type outer cylinder side liquid junction 12B is formed. The variable sleeve 12b is movable in a direction indicated by an arrow in the drawing between a closed position in a use state where the liquid outflow amount from the through hole 12a is equal to or less than a predetermined amount and an open position where the through hole 12b is opened. is there.
[0041]
With such a double junction type liquid junction, when the comparative electrode 1 is immersed in the test liquid S, the inner cylinder inner liquid 13 flows from the inner cylinder 10A to the outer cylinder 10A via the inner cylinder side liquid junction 12A. Flows out little by little, and the inner liquid 16 of the outer cylinder flows out little by little from the outer cylinder 10B to the outside via the outer cylinder side liquid junction 12B, and the comparative electrode 1 is electrically connected to the test liquid S. Be taken.
[0042]
In this embodiment, a 1 mol / L aqueous solution of lithium acetate (CH ₃ COOLi) was used as the liquid 16 inside the outer cylinder as a water-soluble organic acid salt solution. As the inner cylinder inner liquid 13, a 3.3 mol / L KCl aqueous solution (KCL-3.3N, manufactured by Toa DKK Ltd.), which is generally used in the past, was used.
[0043]
Then, the comparison electrode 1 and the pH measurement electrode 2 were immersed in an isopropyl alcohol solution of NaOH as an organic solvent-based test solution, and simultaneously the pH measurement was started, and the subsequent pH indication was recorded. During the pH measurement, the test liquid was appropriately stirred with a magnetic stirrer.
[0044]
As a comparative example, a pH instruction was similarly recorded in a case where a 3.3 mol / L aqueous KCl solution, which is conventionally used, was used as the inner liquid 13 and the inner liquid 16 of the comparative electrode 1. The results are shown in FIG.
[0045]
As can be seen from FIG. 1, in the comparative example in which the 3.3 mol / L KCl aqueous solution was used as the liquid 16 inside the outer cylinder, the pH indication was gradually increased from the start of the measurement, and was still stable even after the measurement time of 18 minutes. The value could not be reached.
[0046]
On the other hand, in this example using a 1 mol / L aqueous solution of lithium acetate as the liquid 16 inside the outer cylinder, the pH value reached a stable value immediately after the start of the measurement, and was maintained thereafter.
[0047]
After the measurement, the inner cylinder side liquid junction 12A and the outer cylinder side liquid junction 12B of the comparative electrode 1 of the present example were observed, but no crystal was found in any of them. Thereafter, the pH was measured again using the comparative electrode 1, and the reproducibility and stability of the pH indication were good.
[0048]
In the present embodiment, the outer cylinder side liquid junction 12B is described as being of a variable sleeve type, but the present invention is not limited to this. According to the present invention, clogging of the liquid junction does not occur and the outflow of the internal liquid is ensured, so that the structure of the liquid junction is not limited. For example, as shown in FIG. 4, the outer cylinder side liquid junction 12B may be a ceramic type. In addition, as the liquid junction, any one known in the art, such as a fiber type, a pinhole type, or a fixed sleeve type, can be used. The fiber type liquid junction has a liquid junction formed in a capillary shape, and the pinhole type liquid junction has a liquid junction formed as a minute through hole. Further, the fixed sleeve corresponds to the one in which the variable sleeve is made immovable. The inner cylinder side liquid junction 12A of the comparative electrode 1 of the present embodiment is not limited to the ceramic type.
[0049]
As described above, according to the present invention, a stable instruction can be obtained in the pH measurement of an organic solvent-based test liquid by an extremely simple method.
[0050]
Example 2
Next, another embodiment of the present invention will be described. In this embodiment, the present invention is embodied in a composite electrode for measuring pH.
[0051]
FIG. 5 shows a schematic cross section of a main part of an embodiment of the composite electrode 3 to which the present invention can be applied. The comparison electrode 1 and the pH measurement electrode 2 have basically the same functions as those of the first embodiment except that they are integrally formed. Therefore, elements having the same functions are denoted by the same reference numerals, and detailed description is omitted.
[0052]
As shown in the figure, the composite electrode 3 is constituted by integrally forming a pH measuring electrode 2 which is a glass electrode and a comparative electrode 1 having a double junction type liquid junction. Here, the outer cylinder side liquid junction portion 12B as the second liquid junction portion in the comparative electrode 1 is of a variable sleeve type. In the present embodiment, the composite electrode 3 has a substantially cylindrical shape, and the pH measurement electrode 2, the inner cylinder 10A of the comparison electrode, and the outer cylinder 10B of the comparison electrode 1 are formed coaxially in this order from substantially inside. ing. The glass film 22 of the pH measurement electrode 2 is formed at the tip of the composite electrode 3 so as to be in contact with the test solution.
[0053]
Similarly to the above, the outer cylinder side liquid junction 12B is not limited to the variable sleeve type, and may be, for example, a ceramic type as shown in FIG. In addition, as the liquid junction, any one known in the art, such as a fiber type, a pinhole type, or a fixed sleeve type, can be used. The inner cylinder side liquid junction 12A is not limited to the ceramic type.
[0054]
In addition, as will be easily understood by those skilled in the art, the composite electrode 3 may be further provided integrally with a temperature detecting means or the like.
[0055]
According to the present invention, a water-soluble organic acid salt solution that does not precipitate crystals when it comes into contact with the organic solvent-based test liquid to be measured is used as the liquid 16 inside the outer cylinder of the composite electrode 3. As a result, the outer cylinder side liquid junction 12B becomes clogged with crystals of the outer cylinder internal liquid 16 while using a high concentration of the reference electrode internal liquid that does not make the measured value unstable due to the effect of the inter-liquid electromotive force. Can be prevented. Further, it is also possible to prevent clogging of the inner cylinder side liquid junction 12A due to crystals, which has conventionally occurred when an organic solvent-based test liquid is used as the inner liquid 16 in the outer cylinder. Therefore, it is possible to avoid problems such as a decrease in responsiveness and stability of the composite electrode 3 in pH measurement of an organic solvent-based test liquid.
[0056]
Further, as the inner cylinder internal liquid 13, a solution that is substantially the same as the internal liquid 23 of the pH measurement electrode 2 is used. As a result, the internally generated potentials of the comparison electrode 1 and the measurement electrode 2 become the same, and the processing of the detection signal in the pH measurement device becomes easy.
[0057]
As described above, by applying the present invention to the composite electrode 3 in which the comparison electrode 1 and the pH measurement electrode 2 are integrally formed, one sensor member can be used as the test liquid in the pH measurement of the organic solvent test liquid. A highly responsive and stable instruction can be obtained by an extremely simple method while taking advantage of the convenience of the composite electrode that can be measured if applied.
[0058]
【The invention's effect】
As described above, according to the present invention, the method for measuring the pH of an organic solvent-based test solution includes a first comparative electrode internal liquid storage section, a second comparative electrode internal liquid storage section, and a first comparative electrode. A first liquid junction for allowing the liquid to flow from the internal liquid container to the second comparative electrode internal liquid container, and a second liquid junction for allowing the liquid to flow from inside the second comparative electrode internal liquid container to the outside. And a liquid junction section, and a comparative electrode using a water-soluble organic acid salt solution is used as the second comparative electrode internal liquid contained in the second comparative electrode internal liquid storage section. With a very simple method, the response is fast, the indication is stable, and a highly reliable measured value can be obtained. Further, according to the present invention, a comparative electrode and a composite electrode embodying the method of the present invention are provided, and the same effects as those of the above-described pH measuring method of the present invention can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the stability of a measured pH value of an organic solvent-based test liquid.
FIG. 2 is a schematic configuration diagram of a pH measurement system to which the present invention can be applied.
FIG. 3 is a schematic cross-sectional view of a main part of an example of a comparative electrode to which the present invention can be applied.
FIG. 4 is a schematic cross-sectional view of a main part of another example of a comparative electrode to which the present invention can be applied.
FIG. 5 is a schematic sectional view of a main part of an example of a composite electrode to which the present invention can be applied.
FIG. 6 is a schematic sectional view of a main part of another example of a composite electrode to which the present invention can be applied.
FIG. 7 is a schematic sectional view of a main part of an example of a conventional composite electrode for pH measurement.
[Explanation of symbols]
1 Reference electrode 2 pH measuring electrode (measuring electrode)
3 Composite electrode 10 Reference electrode internal liquid storage unit 10A Inner cylinder (first reference electrode internal liquid storage unit)
10B outer cylinder (second comparative electrode internal liquid storage part)
11 Reference electrode inner electrode 12 Liquid junction 12b Variable sleeve 12A Inner cylinder side liquid junction (first liquid junction)
12B outer cylinder side liquid junction (second liquid junction)
13 Reference electrode internal liquid, inner cylinder internal liquid 16 Comparative electrode internal liquid, outer cylinder internal liquid 20 Measurement electrode internal liquid storage part 21 Measurement electrode internal electrode 22 Glass film (sensitive film)
23 Liquid inside measurement electrode

Claims

A first comparison electrode internal liquid storage section, a second comparison electrode internal liquid storage section, and a flow of liquid from the first comparison electrode internal liquid storage section to the second comparison electrode internal liquid storage section. A first liquid junction portion; and a second liquid junction portion that allows liquid to flow out of the second comparison electrode internal liquid storage portion to the outside. A method for measuring the pH of an organic solvent-based test liquid, comprising using a comparative electrode using a water-soluble organic acid salt solution as a second internal liquid for a comparative electrode.

The pH measurement method according to claim 1, wherein an alkali metal salt solution of formic acid, acetic acid, propionic acid, and butyric acid is used as the second internal liquid for the comparison electrode.

3. The pH measurement method according to claim 1, wherein the concentration of the second reference electrode internal liquid is 0.1 mol / L to 3 mol / L.

As the first reference electrode internal liquid stored in the first reference electrode internal liquid storage part, a solution that is substantially the same as the internal liquid of the measurement electrode used in combination with the reference electrode is used. 4. The method for measuring pH according to claim 1, wherein the pH is measured.

The pH measurement method according to any one of claims 1 to 4, wherein a potassium chloride solution is used as the first reference electrode internal liquid.

The pH measurement method according to claim 5, wherein the potassium chloride solution is a saturated solution or a 3.3 mol / L solution.

The pH measurement according to any one of claims 1 to 6, wherein the first comparative electrode internal liquid storage section is nested in the second comparison electrode internal liquid storage section. Method.

A first comparison electrode internal liquid storage section, a second comparison electrode internal liquid storage section, and a flow of liquid from the first comparison electrode internal liquid storage section to the second comparison electrode internal liquid storage section is allowed. It has a first liquid junction part and a second liquid junction part that allows the liquid to flow out of the second comparison electrode internal liquid storage part to the outside, and is used for pH measurement of an organic solvent-based test liquid. A reference electrode to obtain,
A comparative electrode, wherein a water-soluble organic acid salt solution is accommodated in the second comparative electrode internal liquid storage section as a second comparative electrode internal liquid.

9. The comparison electrode according to claim 8, wherein a solution of an alkali metal salt of formic acid, acetic acid, propionic acid, and butyric acid is used as the liquid inside the second comparison electrode.

The comparison electrode according to claim 8, wherein a concentration of the second comparison electrode internal liquid is 0.1 mol / L to 3 mol / L.

As the first reference electrode internal liquid stored in the first reference electrode internal liquid storage section, a solution that is substantially the same as the internal liquid of the measurement electrode used in combination with the reference electrode is used. 11. The comparison electrode according to claim 8, 9 or 10, wherein:

The comparison electrode according to any one of claims 8 to 11, wherein a potassium chloride solution is used as the first comparison electrode internal liquid.

13. The comparison electrode according to claim 12, wherein the potassium chloride solution is a saturated solution or 3.3 mol / L.

The comparison electrode according to any one of claims 8 to 13, wherein the first comparison electrode internal liquid storage section is formed in a nested manner inside the second comparison electrode internal liquid storage section. .

A measuring electrode for containing a liquid inside the measuring electrode;
A first comparison electrode internal liquid storage section, a second comparison electrode internal liquid storage section, and a flow of liquid from the first comparison electrode internal liquid storage section to the second comparison electrode internal liquid storage section is allowed. A comparison electrode having a first liquid junction portion and a second liquid junction portion that allows the liquid to flow out of the second liquid storage portion inside the comparison electrode;
Is a composite electrode that can be used for measuring the pH of an organic solvent-based test liquid,
A composite electrode, wherein a water-soluble organic acid salt solution is accommodated in the second comparative electrode internal liquid storage section as the second comparative electrode internal liquid.

The composite electrode according to claim 15, wherein an alkali metal salt of formic acid, acetic acid, propionic acid, and butyric acid is used as the second internal electrode of the comparative electrode.

17. The composite electrode according to claim 15, wherein a concentration of the second reference electrode internal liquid is 0.1 mol / L to 3 mol / L.

18. The composite electrode according to claim 15, wherein the first reference electrode internal liquid contained in the first reference electrode internal liquid is substantially the same as the measurement electrode internal liquid.

The composite electrode according to any one of claims 15 to 18, wherein a potassium chloride solution is used as the first reference electrode internal liquid.

20. The composite electrode according to claim 19, wherein the potassium chloride solution is a saturated solution or a 3.3 mol / L solution.

The composite electrode according to any one of claims 15 to 20, wherein the first comparative electrode internal liquid storage portion is formed in a nested manner in the second comparison electrode internal liquid storage portion. .