1982 Volume 31 Issue 9 Pages 508-513
A simple and automated photometric titration system based on two-phase titration with a porous PTFE (Teflon) membrane as a separating medium of organic phase has been developed. The titrant, cationic surfactant, was added stepwise to a chloroform-aqueous sample solution mixture, which was continuously agitated vigorously by a stirring bar. The chloroform phase was continuously separated by the membrane and monitored at 610 nm. Methylene blue was used as indicator. The titration curve was obtained by converting a transmittance into an absorbance, and the end point was evaluated by extrapolation of linear portion of the curve before and after the end point. The usual samples were analyzed about within 20 min. Various anionic surfactants were analyzed by the proposed method with the coefficient of variation of about 0.9 %. The results were in good agreement with those of manual two-phase titration method developed by Weatherburn.
