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.