A new dodecylsulfate-selective supported liquid membrane electrode based on its N-cetylpyridinium ion-pair

Abstract

A supported liquid and a poly(vinyl chloride) (PVC)-based membrane selective for dodecylsulfate (DS −) ion are described. The active element is a membrane containing a dissolved ion association complex of DS − with cetylpyridinium (CP +) cation. The supported liquid membrane electrode (acetophenone as solvent) showed a Nernstian response towards the DS − anion over the concentration range of sodium dodecylsulfate (SDS) from 8.3×10 −3 to 1.0×10 −6 mol dm −3 at 25 °C. The proposed electrode also showed a super-Nernstian potential response (108±2 mV decade −1) at low concentrations (1.0×10 −9 to 1.0×10 −6 mol dm −3). Moreover, this electrode showed good selectivity and precision (R.S.D.⩽2.0%), and was usable within the pH range 4.0–6.8. The proposed electrode revealed a lower limit of detection of 6.3×10 −7 mol dm −3 and improved selectivity in comparison with the some previously reported DS − ion selective electrodes. The isothermal temperature coefficient of this electrode amounted to −0.001 V °C −1. The liquid membrane electrode may find application in the direct determination of SDS by the standard addition method at pH 5.0, and in the physicochemical studies of surfactant solutions.