A new graphene-based surfactant sensor for the determination of anionic surfactants in real samples

A new high-sensitivity potentiometric all-solid-state sensor for the determination of anionic surfactants is constructed based on the dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) ion pair as a sensing material and graphene. Graphene nanoparticles are used for immobilization of the sensing material in the membrane, preventing the leaching of electroactive material from the membrane, thus reducing its electrical resistance and signal noise. The sensor exhibits a Nernstian response for dodecylbenzenesulfonate (DBS) and a sub-Nernstian response for dodecyl sulfate (DS) in the concentration range of 2.5 x 10(-7)-4.5 x 10(-3) M. The detection limits for DS and DBS are 1.5 x 10(-7) and 2.5 x 10(-7) M, respectively. The sensor demonstrates a stable potentiometric response with a signal drift of -1.2 mV/h and exhibits excellent selectivity performance for DS over almost all of the organic and inorganic anions commonly used in commercial products. The main application of the sensor is in the detection of the endpoint in potentiometric titrations of anionic surfactants. The magnitudes of inflexion at the equivalence point range from 174 to 270 mV. The sensor shows satisfactory analytical performance within a pH range of 2-7. The two-component mixtures containing sodium decanesulfonate (C-10) and sodium dodecanesulfonate (C-12) are also successfully differentially titrated. (C) 2016 Elsevier B.V. All rights reserved.