EFFECT OF HYDROPHOBICITY OF MARKER ANIONS ON THE SENSITIVITY OF END-POINT DETECTION FOR POTENTIOMETRIC TITRATIONS OF ANIONIC POLYELECTROLYTES

A potentiometric titration method is described for the determination of anionic polyelectrolytes using a marker anion and a plasticized poly (Vinyl chloride) membrane electrode sensitive to this marker anion. A solution of an anionic polyelectrolyte, such as potassium poly (vinyl sulfate) (PVSK) added the marker ion has been titrated with a solution of poly (diallyldimethylammonium chloride) (Cat-floc). The end-point has been detected as a sharp potential change due to the rapid decrease in the concentration of the marker ion caused by its association with the titrant, Cat-floc. The sharpness of the end-point of the titration curve has been compared for several marker ions and the dodecylbenzenesulfonate ion was found to be the best among the marker anions studied.