Potentiometric Determination of Dopamine Using a Solid-Contact Polymeric Membrane Ion-Selective Electrode

A simple solid-contact polymeric membrane ion-selective electrode for determination of dopamine was developed. The electrode is fabricated with polymeric membranes incorporating heptakis(2,3,6-tri-o-methyl)-beta-cyclodextrin as ionophore and sodium trakis[3,5-bis(trifluoromethyl)phenyl]borate as ionic additive. Using hydrophobic poly(3-octylthiophene) as solid-contact transducer, the sensor displays a stable potential response for detection of dopamine in 2 mM HAc-NaAc buffer solution (pH 4.4) within a wide concentration range of 3.0 x 10(-5) M-1.0 x 10(-3) M with a sub-Nernstian slope of 43.8 +/- 0.5 mV/dec. The detection limit calculated as the intersection of the two slope lines is 1.3 x 10(-5) M. The electrode exhibits good selectivity over inorganic ions, pharmaceutical excipients and ascorbic acid. In addition, the electrode shows a stable potential response over a wide pH range of 4.0 to 8.5, fast response time (less than 10 s) and excellent repeatability. The proposed electrode has been successfully applied for direct potentiometric determination of dopamine in pharmaceutical formulation without pretreatment procedures

Single-Piece Solid-Contact Polymeric Membrane Ion-Selective Electrodes for Silver Ion

Single-piece solid-contact polymeric membrane Ag+ ion-selective electrodes (ISEs) have been fabricated based on conducting polymer poly(3-octylthiophene) (POT) dissolved into the Ag+ ion-selective membrane. The effects of the amounts of POT on the potential responses of the single-piece solid-contact Ag+-ISEs were investigated in detail. Results indicate that the single-piece solid-contact Ag+-ISE with 10 wt% POT displays excellent reproducibility and stability of the potential response. The linear range of 3.0 x 10(-8)-3.0 x 10(-5) M can be obtained in AgNO3 solution with the slope 56.84 +/- 0.92 mV/dec (n = 3, R = 0.9984) and the detection limit is 1.90 x 10(-8) M. In addition, the single-piece solid-contact Ag+-ISE with 10 wt% POT shows excellent selectivity, stable potential response over a pH range of 3.5 to 6.0 and no significant redox sensitivity. The proposed electrode with 10 wt% POT has been successfully applied to potentiometric titration of chloride ion and determination of Ag+ ion concentrations in spiked waters with high accuracy and good reliability. (C) 2013 The Electrochemical Society