Carbon paste ion-selective electrode for ion-pair formation-based potentiometric titrations of anionic surfactants

Abstract

In this contribution, a new carbon paste ion-selective electrode was introduced for ion-pair formation-based potentiometric titrations of anionic surfactants. In the electrode, an extract of hexadecylpyridinium dodecylsulfate in o-nitrophenyl octyl ether was used as both the binder and the electroactive ion-exchanger. Concerning titrants, three cationic compounds were examined: hexadecylpyridinium chloride (CPC), (diisobutylphenoxyethoxyethyl)-dimethyl-benzylammonium chloride (Hyamine 1622, HYA) and 1,3-didecyl-2-methylimid-azolium chloride (Tegotrant A100, TGT). The last one gave potentiometric titration curves with the highest potential breaks (210-260 mV), followed with CPC (90-140 mV) and HYA (40-60 mV). Despite this, the practical use of TGT in control laboratories should economically be considered impossible for its too high price on market. According to the authors’ meaning, the use of CPC as a titrant seems to be the best compromise as the steepness of the corresponding titration breaks is sufficient and its price is acceptable as well.