Papers by Lenys Mercedes Fernandez Martinez
Scientific Reports, Nov 18, 2023
Electrochimica Acta, Apr 1, 2023
Machala : Ecuador eBooks, 2015
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, Aug 1, 2019
Esta publicación científica en formato digital es continuidad de la revista impresa
Heliyon
The evaluation of glassy carbon (GC) electrodes modified with a Nafion (Nf) film and doped with n... more The evaluation of glassy carbon (GC) electrodes modified with a Nafion (Nf) film and doped with nanoalloys (Nys) deposits of Ag–Hg and Ag–Bi and their application to determination of Cd (II) and Pb(II) in marine sediments, is described. Deposited Ag–Hg and AgBi Nys have a size of approximately ~80 nm dispersed and embedded inside the booths of the Nf net, while other of them remained on Nf net surface. For the AgBiNysNf-GC electrode, a detection limit (DL), 3 s criterion, slightly higher than for the AgHgNysNf-GC modified electrode was obtained. Accuracy of measurements was asserted by comparison with quantification of Cd and Pb in three sets of marine sediments samples previously analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The values of the standard deviation and the coefficients of variation are very low, and also comparable between the different determinations.
Foods
The presence of heavy metals in craft beers can endanger human health if the total metal content ... more The presence of heavy metals in craft beers can endanger human health if the total metal content exceeds the exposure limits recommended by sanitary standards; in addition, they can cause damage to the quality of the beer. In this work, the concentration of Cd(II), Cu(II), and Fe(III) was determined in 13 brands of craft beer with the highest consumption in Quito, Ecuador, by differential pulse anodic stripping voltammetry (DPASV), using as boron-doped diamond (BDD) working electrode. The BDD electrode used has favorable morphological and electrochemical properties for the detection of metals such as Cd(II), Cu(II), and Fe(III). A granular morphology with microcrystals with an average size between 300 and 2000 nm could be verified for the BDD electrode using a scanning electron microscope. Double layer capacitance of the BDD electrode was 0.01412 μF cm−2, a relatively low value; Ipox/Ipred ratios were 0.99 for the potassium ferro-ferricyanide system in BDD, demonstrating that the re...
Frontiers in Chemistry
Treating domestic wastewater has become more and more complicated due to the high content of diff... more Treating domestic wastewater has become more and more complicated due to the high content of different types of detergents. In this context, advanced electro-oxidation (AEO) has become a powerful tool for complex wastewater remediation. The electrochemical degradation of surfactants present in domestic wastewater was carried out using a DiaClean® cell in a recirculation system equipped with boron-doped diamond (BDD) as the anode and stainless steel as the cathode. The effect of recirculation flow (1.5, 4.0 and 7.0 L min−1) and the applied current density (j = 7, 14, 20, 30, 40, and 50 mA cm−2) was studied. The degradation was followed by the concentration of surfactants, chemical oxygen demand (COD), and turbidity. pH value, conductivity, temperature, sulfates, nitrates, phosphates, and chlorides were also evaluated. Toxicity assays were studied through evaluating Chlorella sp. performance at 0, 3, and 7 h of treatment. Finally, the mineralization was followed by total organic carbo...
Cumbres
La presente investigación trata sobre la validación del método de análisis in-situ de Cadmio y Pl... more La presente investigación trata sobre la validación del método de análisis in-situ de Cadmio y Plomo mediante Voltamperometría de Redisolución Anódica en agua de consumo humano, con la posibilidad de ser aplicado in situ. Los parámetros de validación fueron: incertidumbre, linealidad, sensibilidad, límite de detección y cuantificación, precisión y exactitud. Fue evaluado el método en dos rangos de trabajo. El coeficiente de repetibilidad para Cadmio en rango bajo fue del 10.4% y en el alto fue de 9.07%, mientras que en la reproducibilidad se obtuvo para el rango bajo 1.56% y en el rango alto fue de 0.10%, por su parte la exactitud obtenida como porcentaje de recuperación fue del 93 % para el rango bajo y del 117.75 % para el rango alto. En cuanto al coeficiente de repetibilidad de Plomo presentó en rango bajo de 7.13% y en el rango alto de 11.60%, y para la reproducibilidad en el rango bajo se obtuvo 0.02919% y para el rango alto 0.60%, por su parte, la exactitud para el caso del...
Sensing and Bio-Sensing Research
SSRN Electronic Journal, 2021
Metallic ions release from orthodontic brackets and wires mostly depends on quality (chemical com... more Metallic ions release from orthodontic brackets and wires mostly depends on quality (chemical composition) and the medium to which it is exposed, e.g. acid, alkali, substances with high fluorine concentration, etc. Among a heterogenous group of research, it was reported that stainless steel, which is used in orthodontic stuff, is the material that suffers most wear. It was apparent that dissolutions with acid pH, alcohols, fluorides, and chlorides aggravate the orthodontic material corrosion. Otherwise, nickel release from brackets and wires can cause allergic reactions to patients. This review addressed corrosion and wear of orthodontic brackets, wires and arches exposed to different media: beverages (juices), mouthwashes, artificial saliva, etc., and the possible health effects that can be caused by releasing of metallic ions under several conditions.
Sensing and Bio-Sensing Research, 2021
Nanoscience & Nanotechnology-Asia, 2020
Mercury (Hg) contamination is a problem that currently affects not only the environment but also ... more Mercury (Hg) contamination is a problem that currently affects not only the environment but also human health. Various types of commercial adsorbents have been proposed for its removal. Silver is a noble element that can chemically adsorb mercury, forming amalgams. However, its use as an adsorbent presents the following disadvantages: rapid surface saturation and high cost. These limitations can easily be overcome using silver nanoparticles (AgNPs). With a size of less than 100 nm, their reactivity, their high surface area, and a minimal amount of metallic precursor, they are ideal candidates for mercury removal. This study presents a compendium of the use of conventional mercury adsorbents and the use of AgNPs for their colorimetric detection and removal in different matrices, in both the aqueous and gas phases of Hg0 and Hg2+ . In addition, the number of patents available in each case is analyzed. AgNPs as colorimetric sensors allow for quick detection of mercury in-situ. Addition...
Chemical Physics Letters, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
infoANALÍTICA, 2019
El aumento poblacional y el desarrollo tecnológico ha ocasionado una gran demanda energética, lo ... more El aumento poblacional y el desarrollo tecnológico ha ocasionado una gran demanda energética, lo que ha dado paso a que varios grupos de investigación incursionen en la búsqueda de soluciones a corto y mediano plazo. El uso de tecnologías que permitan tratar aguas contaminadas y la generación simultánea de energía eléctrica surge como una alternativa viable para dar solución a este problema. En este documento se revisa el mecanismo para el tratamiento de agua residual y la generación de energía eléctrica simultánea, a través de sistemas combinados de humedales acoplados a celdas de combustible microbianas (CW-MFC, por sus siglas en inglés). El objetivo de esta revisión es describir los componentes y funcionamiento de los sistemas individuales CW y MFC, así como también del sistema combinado CW-MFC, los cuales han sido empleados en investigaciones recientes. Se exploran los principales estudios, relacionados con el material con el cual se construyen los electrodos, que generen mayor ...
Talanta, 1986
The formation constants of some Hg(I1) complexes have been determined from the anodic polarograph... more The formation constants of some Hg(I1) complexes have been determined from the anodic polarographic signals for the oxidation of mercury in the presence of the following ligands: thiourea and its phenyl-and diphenyl-derivatives, thiocyanate, ethylenediamine, EDTA, methylthioacetic acid, 2,2'-thiobisacetic acid, 3,3'-thiobispropanoic acid, 2,2'-[l,l-methandiylbis(thio)]bisacetic acid and 2,2'-[1,2-ethandiylbis(thio)]bisacetic acid. The use of differential pulse polarography and a.c. polarography instead of d.c. polarography increases the accuracy and precision of the potential measurements and, as a consequence, of the stability constants determined. The results obtained by the different methods are compared.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1988
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Papers by Lenys Mercedes Fernandez Martinez