Search

Abstract  A new salicylate-selective electrode based on the complex (2,3;6,7;10,11;14,15-tetraphenyl-4,9,13,16-tetraoxo-1,5,8,12-tetraazacyclohexadecane) copper(II) [CuL] as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of −60.9 ± 1.0 mV/decade and a linear range from 1.0 × 10−6 to 1.0 × 10−1 M for salicylate. The detection limit is 5.0 × 10−7 M. The electrode has a fast response time (5–15 s) and can be used for more than three months. The selective coefficients were determined by the fixed interference method (FIM) and separate solution method (SSM). The salicylate-selective electrode could be used in the pH range 3.5–10.5. It was employed as an indicator electrode for direct determination of salicylate in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

Abstract  By immobilizing rutin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWCNT), a new modified electrode has been fabricated and its electrochemical behavior was investigated by cyclic voltammetry. Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple with surface confined characteristics. The results show that the reversibility of rutin is significantly improved at a MWCNT modified GCE in comparison with GCE alone. The charge transfer coefficient, α, was calculated to be 0.4, and charge transfer rate constant, ks, was 46.7 s−1 in pH 8, indicating great facilitation of the electron transfer between rutin and MWCNT deposited on the electrode surface. The rutin MWCNT (RMWCNT) modified GCE showed excellent mediation of hydrazine oxidation: a decrease in the overvoltage of hydrazine electrooxidation was observed as well as a dramatic increase in the peak current compared to that seen at a rutin modified GCE (RMGCE), activated GCE or bare GCE. Hydrazine was determined amperometrically at the surface of RMWCNT modified GCE in pH 8. Under the optimized conditions the calibration curve is linear in the concentration range 2.0–190.0 μM hydrazine. The detection limit and sensitivity are 0.61 μM and 0.0656 μA μM−1, respectively. Finally the kinetic parameters of the electron transfer coefficient, α, the heterogeneous rate constant of dependent to different potentials, k′(E), and the standard heterogeneous rate constant, k0, for oxidation of hydrazine at the RMWCNT surface were determined using various electrochemical methods. The advantages of this modified electrode for hydrazine determination are high sensitivity, excellent catalytic activity, short response time, wide linear range, and high exchange current density. [ABSTRACT FROM AUTHOR]