流動電位検出/イオン会合滴定法による陽イオン界面活性剤の迅速定量

An ion-association titration method coupled with a streaming potential detector was developed for the determination of cationic surfactants in a one-phase aqueous system. Dodecyl sulfate ion (LS-) was used as a titrant for cationic surfactants in a direct titration method. LS- was added to a cationic surfactant solution, and a potential change from positive to negative was observed. The end point was read from an inflection point of a differential curve. Direct and indirect titration methods for the determination of cationic surfactants were examined. The direct titration method was better than the in- direct titration method with respect to the precision. The usual samples were titrated within 10 min. Cationic surfactants at concentrations from 10-510-3 mol dm-3 could be determined by the proposed method. Amine and quaternary ammonium salts could be determined under both acidic and alkaline conditions. The proposed method was applied to the determination of various cationic surfactants and cationic surfactants in commercial detergents. The results obtained by the proposed method were in good agreement with those of the JIS titration method (Epton method).

流動電位検出器を用いたイオン会合滴定法による陽イオン界面活性剤の迅速定量法を開発した.本法は, 陽イオン界面活性剤を陰イオン界面活性剤で滴定するもので, 流動電位が正から負に変化することを利用して終点検出を行うものである.検出原理及び装置は非常に簡単なもので, 従来のクロロホルム溶媒を用いない水溶液系で行うことができる.10(-5)～10(-3)Mの濃度範囲の陽イオン界面活性剤を迅速自動定量 (10分/件) できる.直接滴定法と逆滴定法について検討した結果, 直接滴定法のほうが逆滴定法に比べて再現性の面で優れていることが分かった.陽イオン界面活性剤の各種標準及び実際試料の応用について検討した結果, 分析値はJIS法 (Epton法) と非常に良い一致を示し, 再現性も良好であった.更に, 酸性及びアルカリ性条件下での測定により, アミン塩及び四級アンモニウム塩の分別定量も可能となった.