Application of an all-solid-state ion-selective electrode for the automated titration of anionic surfactants

Abstract

A poly(vinyl chloride) matrix membrane electrode responsive to anionic surfactants in an all-solid-state graphite–epoxy support was applied to the determination of anionic surfactants by potentiometric titration, using Hyamine 1622 as the titrant, in a pH 2.2 phosphate buffer. The results from this method compare favourably with those of the two-phase mixed indicator titration method for several commercial anionic surfactants (alkylsulfates, alkylbenzenesulfonates, α-alkene sulfonates, alkyl ether sulfates and sulfosuccinates). The performance characteristics improve the commercially available surfactant electrodes: the standard deviation for the titration of 4 mmol dm^–3 dodecylsulfate with 4 mmol dm^–3 titrant is 0.15%(n= 23), the relative standard deviation of the end-point potential is 0.95% and the average value of the potential jump is 140 mV, which allows for the titration of surfactants at concentrations down to 10 µmol dm^–3 and shows its applicability in routine analysis.