強電解酸性水の残留塩素濃度測定が可能なメタクリル酸銀検知液の開発  [in Japanese] Development of Trial Chemical Solution Liquefying Silver Methacrylate for Detecting and Measuring Residual Chlorine in Electrolyzed Strongly Acidic Water  [in Japanese]

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Author(s)

    • 吉田 康一 Koichi YOSHIDA
    • 東邦歯科医療専門学校|朝日大学歯学部口腔機能修復学講座歯科保存学分野歯内療法学 Toho Dental College|Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry
    • 吉田 隆一 Takakazu YOSHIDA
    • 朝日大学歯学部口腔機能修復学講座歯科保存学分野歯内療法学 Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry

Abstract

 目的 : メタクリル酸銀は純水には溶解度の低い有機金属化合物であるが, 親水基をもつ有機溶媒に対してこれを溶解した水溶液中の銀イオンは, 塩素イオンとごく微量でも反応し, 水に難溶性の塩化銀として析出し水溶液が白濁する. この原理を応用することで, 溶解液によって水中の塩素イオンの有無やその量を計測することが可能となる. 独自に合成したメタクリル酸銀に有機溶剤を添加することによって, 強電解酸性水中の塩素含有量の測定が可能な外添加用検知液の新規開発を試みた. <br> 材料と方法 : 検知液の作成にあたっては, 合成物を水溶性とするために5種類の水溶性有機溶剤 : アクリル酸, ホルムアルデヒド, N.N-ジメチルホルムアミド, 乳酸, アセトニトリルを選択し, メタクリル酸銀をそれぞれ0.01, 0.1, 0.5 wt%混合, 溶解した. 次に, 歯科領域で手術野や感染根管の消毒などに応用されている強電解酸性水の原液を, 超純水で0, 2, 4, 8, 16, 32, 64倍の各濃度に希釈した試験液を作成した. さらに, 残留塩素をわずかながら含む水道水や全く含まない超純水中に検知液を微量添加し, 生じた白濁による光の透過性の変化を, 紫外・可視分光光度計にて透過率 : Transmission (%T), 入射光 : 300nmの計測条件で注入から0, 30, 60分後にそれぞれ測定した. 得られた測定値を四元配置分散分析し, 残留塩素濃度測定液として実用上, 最適な溶剤種と濃度の検討ならびに, 検知液種ごとに注入後の最適測定時間を調べた. さらに各種検知液を, 各希釈倍率の強電解酸性水の検知液注入前の残留塩素濃度 (ppm) の数値と, 検知液の添加によって塩化銀が生成し変化した透過率 (%T) との間で, 相関・回帰分析を行い検討した. <br> 成績 : 使用溶剤種, メタクリル酸銀濃度, 検知液添加 (注入) 後の経過時間, 強電解酸性水の希釈倍率のすべての主効果と交互作用に有意差が認められた. また, 溶剤としてアセトニトリル, N.N-ジメチルホルムアミド, 乳酸を使用した検知液は, 酸性水への添加後の経時的な性状の変化が30分以上では少なく安定しており, 塩素イオンとの反応性もよく希釈倍率に応じた透過率の変化を示していた. 回帰分析を行った結果, メタクリル酸銀濃度0.01 wt%のN.N-ジメチルホルムアミド溶剤 (純度99.5%) を使用した検知液では, 0, 30, 60分の条件で検量線が得られ, 60分ではy=-0.081x+97.031 (r=0.9605<sup>**</sup>) であった. <br> 結論 : 今回作成した検知液は, 酸性水への注入後0∼60分で使用できるものもあり, 酸性水へも低濃度のメタクリル酸銀を微量作用させることで大きな混濁をもたらす. そのため, 実用的な歯科用酸性水の高濃度から低濃度までの残留塩素濃度測定液として使用可能なものと考えられ, 実際の歯科臨床での応用が期待できる.

 Purpose: The solubility of synthesized organometallic compound silver methacrylate in pure water is very low. However, by liquefying silver-methacrylate in an aqueous solution which possesses a hydrophilic group, silver ions can react with even trace amounts of chloride ions to form silver chloride, which is insoluble in water and causes cloudiness. The application of this principle enables the amount of chloride ions in water to be determined. We have developed a new detection solution by synthesizing a particular silver methacrylate compound and adding it to various organic solvents, which can measure the content of chloride ions in electrolyzed strongly acidic water.<br> Methods: To develop a system for determining the quantity of residual chloride in water, 0.01, 0.1, and 0.5 wt% silver methacrylate were dissolved in five water-soluble organic solvents (formaldehyde, acetonitrile, <i>N</i>, <i>N</i>-dimethylformamide, lactic acid, and acrylic acid) to produce a detection solution. The solution was poured into electrolyzed strongly acidic water. The acidic water was diluted using ultrapure water 0, 2, 4, 8, 16, 32, and 64 times. We measured the changes in the permeability of its cloudiness, based on the flux of light from an ultraviolet-visible spectrometer after 0, 30, and 60 min (mode:% transmission, 300 nm). The data (%T) were analyzed using four-way analysis of variables (ANOVA; Factor A: solvent, B: silver methacrylate content (wt%, as solute), C: reaction time from flooding, and D: dilution factor of electrolyzed acidic water). We identified the best conditions for practical applications. Next, using the same data, regression analysis was applied to the value of the residual chloride content (ppm) of the electrolyzed water at each dilution factor before flooding with the detection solution, and the corresponding transmission factor (%T) after flooding with the detection solution.<br> Results: ANOVA showed significant differences among all the main effects and interactions. In three types of detection solution, the %T values of each acidic water hardly changed for reaction times exceeding 30 min. Additionally, their reactivities with chloride ions were excellent, and the changes in %T corresponded to the dilution factor of the electrolyzed acidic water. Regression analysis was significant in constructing a calibration curve for a detection solution consisting of <i>N</i>, <i>N</i>-dimethylformamide (purity: 99.5%) and 0.01 wt% silver methacrylate, for reaction times of 0, 30, and 60 min. A reaction time of 60 min gave <i>y</i>=−0.081<i>x</i>+97.031 (<i>r</i>=0.9605<sup>**</sup>).<br> Conclusion: These results show that our detection solution is suitable for practical applications, and can be used to determine the amount of residual chloride in electrolyzed acidic water in dentistry.

Journal

  • The Japanese Journal of Conservative Dentistry

    The Japanese Journal of Conservative Dentistry 57(1), 43-57, 2014

    The Japanese Society of Conservative Dentistry

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