A new sensitive potentiometric surfactant sensor was prepared based on a highly lipophilic 1, 3-didecyl-2-methyl-imidazolium (DMI) cation and a tetraphenylborate (TPB) antagonist ion. This compound was used as a sensing material and incorporated into the plasticized PVC-membrane. The sensor responded fast and showed a Nernstian response for all the investigated cationic surfactants: 59.8 mV/decade for cetylpyridinium chloride (CPC), 58.6 mV/decade for hexadecyltrimethylammonium bromide (CTAB), and 56.8 mV/decade for Hyamine. The sensor served as an end-point detector in ion-pair surfactant potentiometric titrations using sodium tetraphenylborate as titrant, and displayed satisfactory analytical performances within a pH range of two to eleven. The influence of the ethoxylated alcohols (EONS), a widely used class of nonionic surfactants on the shape of titration curves was negligible if the mass ratio of EONS:CS was not greater than five. The selectivity coefficients were determined by fitting the Nikolskii-Eisenman equation to the experimental data obtained by the mixed solution method. The sensor exhibited excellent selectivity performances for CPC over all organic and inorganic cations investigated. Several commercial disinfectant products containing various cationic surfactants were potentiometrically titrated using the new DMI-TPB sensor as an indicator.

Chemistry