Examinando por Autor "Nuñez-Dallos, Nelson"
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- PublicaciónSólo datosIn situ-Mercury Film Electrode for Simultaneous Determination of Lead and Cadmium Using Nafion Coated New Coumarin Schiff Base as Chelating-Adsorbent(International Journal of Electrochemical Sciences, 2016-11-10) Nuñez-Dallos, Nelson; Cuadrado, Carol; Hurtado, John; Nagles, Edgar; García-Beltrán, OlimpoReaction of o-phenylenediamine and 8-formyl-7-hydroxycoumarin yield a new coumarin salen ligand, (CSB) which was isolated as orange air-stable solid and characterized by melting point, thermogravimetric analysis (TGA), mass spectra, infrared and NMR (1H, 13C) spectroscopy. New CSB was dispersed in nafion and nafion-CSB composite was deposited on a glassy carbon electrode. The modified electrode nafion-CSB/GCE allowed the formation in-situ of mercury film for detection of Pb (II) and Cd(II) by anodic stripping voltammetry (ASV) in buffer phosphate solution pH 3.0 and 4.0. Optimal conditions were studied (mercury concentration: CHg 40.0 mg L-1 ; CSB concentración; CCSB; 20.0 µmol L-1 ; pH 3.0 and pH 4.0; EACC:-1.1 V and tACC: 80).The detection limit (3σ/b) for Pb (II) Cd (II) were of 0.15 µg L–1 for Pb(II) and Cd(II) at pH 3.0. Moreover, 0.071 and 0.080 µg L–1 for Pb(II) and Cd(II), respectively at pH 4.0, The method was validated using ICP multi-element standard solution IX (Merck) containing As, Be, Cd, Cr(VI), Hg, Ni, Pb, Se and Tl 100 mg L-1 . Finally, river, tap and mineral waters were analyzed.
- PublicaciónSólo datosVoltammetric determination of amaranth and tartrazine with a new double-stranded copper(I) helicate-single-walled carbon nanotube modified screen printed electrode(Journal of Electroanalytical Chemistry, 2018-05-26) Nuñez-Dallos, Nelson; Macías, Mario; García-Beltrán, Olimpo; Calderón, Jorge A.; Nagles, Edgar; Hurtado, JohnIn this work, we report the synthesis of a new double-stranded copper(I) helicate (H) and its use for the first time in a single-walled carbon nanotube-modified screen printed electrode (SWCNT/SPCE) for the voltammetric determination of amaranth (AM) and tartrazine (TZ). H was synthesized through a self-assembly process between Cu(I) iodide and 1,3-bis(1H-benzotriazol-1-ylcarbonyl)benzene (L). The compound was structurally characterized by infrared, photoluminescence spectroscopy, elemental and thermogravimetric analyses as well as single-crystal and powder X-ray diffraction. The SWCNT/SPCE was coated with H by simple drop casting, and the surface (H-SWCNT/SPCE) was characterized using cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The presence of H on the surface of the modified electrode reduces the charge transfer resistance of the redox couple and improves the sensitivity toward the oxidation of AM and TZ with oxidation current increases of almost 80% and 60%, respectively, thus allowing their determination using square-wave adsorptive stripping voltammetry (SWAdSV). The detection limits (3σ/b) were 30.0 and 60.0 nmol L−1 for AM and TZ, respectively. The relative standard derivation was 3.5% (n = 7) with three different electrodes. Furthermore, the new sensor was applied in the detection of these dyes in commercial samples such as synthetic orange juice and a soft drink.