Now showing items 1-20 of 224

    • 1,3-Dioxolane: A green solvent for the preparation of carbon nanotube-modified electrodes 

      Moscoso, R.; Carbajo, J.; Squella Serrano, Juan (Elsevier Inc., 2014)
      © 2014 Elsevier B.V. One of the main challenges associated with the handling of carbon nanotubes (CNTs) for modifying electrodes is the production of adequate dispersions. We report the first example in which 1,3-dioxolane ...
    • 1,4-Dihydropyridines: Reactivity of nitrosoaryl and nitroaryl derivatives with alkylperoxyl radicals and ABTS radical cation 

      Valenzuela, V.; Santander, P.; Camargo Grandón, Rodrigo; Squella Serrano, Juan; López Alarcón, Camilo Ignacio; Núñez Vergara, Luis (TAYLOR & FRANCIS, 2004-07)
      In the present paper, a direct quenching of radical species by a number of synthesized nitrosoaryl 1,4-dihydropyridines and their parent nitroaryl 1,4-dihydropyridines was determined in aqueous media at pH 7.4. These two ...
    • A DPP study of ranitidine permeability 

      Núñez Vergara, Luis; Donoso, G.; Roman, A.; Squella Serrano, Juan (1988)
      The apparent permeation rate constants and amount of ranitidine transferred in 1 h were measured through everted rat intestine using a perfusion apparatus. The effects of pH and 5% or 10% ethanol on the apparent permeation ...
    • A DPP study of ranitidine permeability 

      Núñez Vergara, Luis; Donoso, G.; Roman, A.; Squella Serrano, Juan (1988)
      The apparent permeation rate constants and amount of ranitidine transferred in 1 h were measured through everted rat intestine using a perfusion apparatus. The effects of pH and 5% or 10% ethanol on the apparent permeation ...
    • A nitro radical anion formation from nifedipine: an electrochemical approach 

      Squella Serrano, Juan; Solabarrieta, C.; Núñez Vergara, Luis (1993)
      The cyclic voltammetric behaviour of nifedipine was studied. The addition of three aprotic solvents to nifedipine in an aqueous citrate buffer system was examined. Qualitatively they result in separation of the initial ...
    • A non-conventional way to perform voltammetry 

      Moscoso, R.; Inostroza, E.; Squella Serrano, Juan (Elsevier, 2017)
      In a conventional voltammetric experiment, the electroactive species is dissolved in solution, and then diffuses from the solution phase to the electrode phase. In our proposed non-conventional voltammetric experiment, ...
    • A polarographic study of the photodegradation of nitrendipine 

      Squella Serrano, Juan; Zanocco, A.; Perna, S.; Núñez Vergara, Luis (1990)
      Nitrendipine produces a well-defined polarographic peak due to the four-electron reduction of the nitro group. This peak is used for tracking the photodecomposition of nitrendipine in both UV light and daylight conditions. ...
    • A simple derivatization of multiwalled carbon nanotubes with nitroaromatics in aqueous media: Modification with nitroso/hydroxylamine groups 

      Moscoso Cabello, Raúl Andrés; Carbajo, J.; López, M.; Núñez Vergara, Luis; Squella Serrano, Juan (ELSEVIER SCIENCE INC, 2011-02)
      We report that GCE modified with MWCNTs can be derivatized by the nitroaromatic drug nitrendipine (NTD) ((RS)-ethyl methyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate) simply by dipping the electrode ...
    • Activity of boldine on rat ileum 

      Speisky Cosoy, Hernán; Squella Serrano, Juan; Núñez Vergara, Luis (1991)
      Boldine shows a concentration-dependent relaxation effect on the rat ileum preparation with a pD2 of 3.77 ± 0.12. The alkaloid also produces a concentration-dependent parallel shift of the curve-response to acetylcholine, ...
    • Acyclovir: Voltammetric behaviour and analytical application to pharmaceutical forms 

      Álvarez Lueje, Alejandro; Núñez Vergara, Luis; Vicuna,; Squella Serrano, Juan (1996)
      The electrochemical oxidation of acyclovir at different pH and concentrations using both differential pulse and cyclic voltammetry was studied. Acyclovir exhibits one differential pulse voltammetric peak at the glassy ...
    • Adsorption of ochratoxin A (OTA) anodic oxidation product on glassy carbon electrodes in highly acidic reaction media: Its thermodynamic and kinetics characterization 

      Ramírez, Eduardo Alejandro; Zon, María Alicia; Jara Ulloa, Paola Andrea; Squella Serrano, Juan; Núñez Vergara, Luis; Fernández, Héctor (PERGAMON-ELSEVIER SCIENCE LTD, 2010-01-01)
      We study the thermodynamics and kinetics of the adsorption of a redox couple having quinone nature on glassy carbon electrodes. This couple is produced by the anodic oxidation of mycotoxin ochratoxin A in 10% acetonitrile ...
    • Adsorptive stripping voltammetric determination of nitroimidazole derivative on multiwalled carbon nanotube modified electrodes: Influence of size and functionalization of nanotubes 

      Jara Ulloa, Paola Andrea; Cañete Rosales, Paulina; Núñez Vergara, Luis; Squella Serrano, Juan (2011)
      1-Methyl-4-nitro-2-brominemethylimidazole (4-NimMeBr), was electrochemically reduced on mercury, glassy carbon and multiwalled carbon nanotubes (MWCNT) modified electrodes. 4-NimMeBr was adsorbed on the MWCNT modified ...
    • An electroactive metabolite from amoxycillin 

      Núñez Vergara, Luis; Daza, R.; Zanocco, A.; Squella Serrano, Juan (1983)
      2-Hydroxy-3-(p-hydroxyphenyl)-6-methylpyrazine (HHMP) is identified as the product obtained by acidic degradation of amoxycillin in the presence of formaldehyde. I.R., n.m.r. and elemental analysis data are reported. The ...
    • Analyses by GC-MS and GC-MS-MS of the hantzsch synthesis products using hydroxy- and methoxy-aromatic aldehydes 

      Núñez Vergara, Luis; Navarrete Encina, Patricio; Salas, S.; Conde, B.; Carbajo, J.; Squella Serrano, Juan; Camargo Grandón, Rodrigo (PERGAMON-ELSEVIER SCIENCE, 2007-05-09)
      El mass spectra of products of the dihydropyridine Hantzsch synthesis using hydroxy and methoxy aldehydes as starting materials are reported. The reaction products (C-4 hydroxy- and methoxyphenyl-1,4-dihydropyridines and ...
    • Anodic Polarographic Behaviour of Hydrolyzed 

      Squella Serrano, Juan; Núñez Vergara, Luis (1982)
      The electroactivity of a degradation product from penicillin V is described.This electroactive product is formed by acidic hydrolysis at pH 4.0 and heating at 90QC for 60 minutes. This derivative has not been identified, ...
    • Anodic polarographic determination of flucloxacillin 

      Squella Serrano, Juan; Silva,; Núñez Vergara, Luis (1981)
      The hydrolysis of flucloxacillin at pH 4.9 yields a degradation product which is polarographically oxidizable. This derivative has not been identified, but would seem to contain a thiol group. It gives a diffusion-controlled ...
    • Antioxidant activity of gallates: an electrochemical study in aqueous media 

      Gunckel Ulisse, María Soledad; Santander Gutiérrez, Ingrid Paola; Cordano, G.; Ferreira Parker, Jorge; Muñoz, S.; Núñez Vergara, Luis; Squella Serrano, Juan (ELSEVIER SCI IRELAND, 1998-07-03)
      The electron-donating ability of gallates, which are food and pharmaceutical antioxidants, is quantitatively assessed on the basis of their electrochemical characteristics. Gallic acid and the propyl, i-propyl, butyl, ...
    • Antioxidant effects of 1,4-dihydropyridine and nitroso aryl derivatives on the Fe+3/ascorbate-stimulated lipid peroxidation in rat brain slices 

      Díaz Araya, Guillermo; Godoy Oviedo, Luis; Naranjo, Luis; Squella Serrano, Juan; Letelier Muñoz, María Eugenia; Núñez Vergara, Luis (PERGAMON-ELSEVIER SCIENCE, 1998-09)
      1. Lipid peroxidation in rat brain slices was induced by Fe+3/ascorbate. 2. Brain lipid peroxidation, as measured by malondialdehyde formation, was inhibited by all the tested nitro aryl 1,4-dihydropyridine derivatives ...
    • Assessment of the hydrolytic degradation of lovastatin by HPLC 

      Álvarez Lueje, Alejandro; Pastine Sepúlveda, Javiera; Squella Serrano, Juan; Núñez Vergara, Luis (SOCIEDAD CHILENA DE QUIMICA, 2005-12)
      In this work an HPLC stability-indicating method was developed and applied to study the hydrolytic behaviour of lovastatin in different simulated fluids. The selected chromatographic conditions were a C-18 column, ...
    • Caracterización electroquímica de 4-nitroimidazoles efecto del substituyente en posición 1 

      Cutiño López, Eduardo Andrés (Universidad de Chile, 2007)
      Se realizó un estudio voltamétrico de dos compuestos 4-nitroimidazólicos los que presentan diferentes substituyentes (-H, -CH3) en la posición 1 del anillo imidazólico. Se determinó el comportamiento electroquímico en medio ...