Titrimetric determination of anionic surfactant content in anionic/nonionic surfactant mixture solution by anionic surfactant selective electrode

A new polyvinyl chloride (PVC) membrane electrode for determining the concentration of sodium dodecylsulfate (SDS) based on a neutral ion pair complex of dodecyltrimethylammonium-dodecylsulfate (DTA(+)DS(-)) as ionophore is described in this paper. The construction and characteristic performance of the PVC membrane electrode displays a Nernstian slope of -56.9 +/- 0.3 mV/decade in the concentration range of 2.0 x 10(-6) to 3.2 x 10(-3) mol L-1 and a detection limit of 1.6 x 10(-6) mol L-1. The lifetime of the electrode is more than 3 months without showing significant change in the values of slope or linear concentration range. The electrode has wide pH range of application and short response time. The electrode shows selective response to DS- and poor response to common anions except DBS-. The electrode was used as an end point indicator electrode for the determination of SDS content in sodium dodecylsulfate/nonylphenol ethoxylates (SDS/NP-10) mixture solution by potentiometric titration using Hyamine standard solution as titrant. The maximum mol ratio (n((NP-10)): n((SDS))) when SDS cannot be determined in SDS/NP-10 mixture solution can be obtained.