New tetradecyltrimethylammonium-selective electrodes: Surface composition and topography as correlated with electrode's life span

Two conventional plastic membrane electrodes that are selective for the tetradecyltrimethylammonium cation (TTA) have been prepared. The ion exchangers of these sensors were the ion associate, TTA-PT, and the ion aggregate, TTA-PSS, where PT and PSS are phosphotungstate and polystyrene sulfonate, respectively. The following performance characteristics of the TTA-PT- and TTA-PSS-containing electrodes were found: conditioning time of 30 and 20 min; potential response of 58.2 and 61.1 mV/TTA concentration decade; rectilinear concentration ranges of 2.0 × 10−5–5.0 × 10−2 and 1.5 × 10−5–7.9 × 10−2 mol L−1; average working pH ranges of 4.0–10.5 and 3.8–10.7; life spans of 20 and 28 weeks, and isothermal temperature coefficients of 4.44 × 10−4 and 6.10 × 10−4 V/°C, respectively. Both electrodes exhibited high selectivity for TTA with an increasing number of inorganic and quaternary ammonium surfactant cations. These electrodes have been successfully applied to assay an antiseptic formulation containing TTA. Surface analyses using electron microscopy and X-ray photoelectron spectroscopy were used to determine the cause of the limited life span of plastic membrane electrodes.

► Novel tetradecylltrimethylammonium-electrodes with excellent performance characteristics were developed.
► Ion aggregate and ion associate are very successful as cation exchangers for surfactant's plastic membrane electrode.
► Electron microscopy of fresh and used electrodes proved that topographical change at the surface of the electrode, as a result of soaking in the test solution, contributes to limitation of its life span.
► X-ray photoelectron spectroscopy was used to monitor the leaching of ingredient from surface of plastic membrane electrode.