Immobilization of Acetylcholinesterase on Screen-Printed Electrodes. Application to the Determination of Arsenic(III)

Enzymatic amperometric procedures for measuring arsenic, based on the inhibitive action of this metal on acetylcholinesterase enzyme activity, have been developed. Screen-printed carbon electrodes (SPCEs) were used with acetylcholinesterase covalently bonded directly to its surface. The amperometric response of acetylcholinesterase was affected by the presence of arsenic ions, which caused a decrease in the current intensity. The experimental optimum working conditions of pH, substrate concentration and potential applied, were established. Under these conditions, repeatability and reproducibility of biosensors were determined, reaching values below 4% in terms of relative standard deviation. The detection limit obtained for arsenic was 1.1 × 10−8 M for Ach/SPCE biosensor. Analysis of the possible effect of the presence of foreign ions in the solution was performed. The method was applied to determine levels of arsenic in spiked tap water samples.Junta de Castilla y León (BU022A07, Q0968272E) and the Ministerio de Ciencia e Innovación (TEC2008-01367/TEC) is gratefully acknowledged

Political parties and encouragement of participation in electoral period: analysis of messages and comments on facebook during general elections, 2015

Los primeros años del siglo XXI iniciaron un uso de Internet durante campaña que pretendía potenciar el impacto mediático de los candidatos. No fue hasta 2008, con Barack Obama, cuando se planteó la utilización de las herramientas electrónicas como un elemento dinamizador y movilizador durante esos periodos. Aplicado al caso de Facebook, en esta investigación nos preguntamos si durante las elecciones de 2015 los partidos políticos españoles fueron capaces de aprovechar los flujos de comunicación digital para activar la participación de su comunidad. A través de un análisis de contenido de los post de estas organizaciones (839) y los comentarios publicados en estos (193.682) comprobamos que el uso mayoritario de esta red social se centra en la promoción de la actividad electoral del candidato presidenciable y que más del noventa por ciento de los usuarios no siguen hashtags ni otras referencias a la campaña electoral.During first years of the 21st century, Internet began to be used to enhance the media impact of the candidates in campaign. In 2008, when Barack Obama aimed to the USA presidency, the use of electronic tools was considered as a dynamic and mobilizing element during those periods. This investigation applies this theoretical field to Facebook in Spanish elections, 2015. We wonder if political parties were able to take advantage of the flows of digital communication to encourage participation of their community. We address a content analysis of the post of these organizations (839) and the comments published in these (193,682). We found that use of this social network mostly focuses on promoting the presidential candidate's electoral activity. Furthermore, more than ninety percent of users do not follow hashtags or other references to the election campaign.Ministerio de Economía y Competitividad CSO2016-78386-

4-ethyphenol detection in wine by fullerene modified screen-printed carbon electrodes

This work shows the potential of modified screen-printed carbon electrodes (SPCEs) for sensitive and selective detection of 4-ethylphenol in wine. Gold nanoparticles (AuNPs) and fullerene C60 (C60), modified sensors have been compared. pH of the supporting electrolyte, deposition time and working temperature have been optimized considering their influence in the voltammetric pulse response of 4-ethylphenol. Under the optimal conditions of measurement, the developed activated C60/SPCE (AC60/SPCE) shows the best performance, with a detection capability of 400 μg/L and 700 μg/L, when using deposition times of 14 min and 6 min, respectively (α = β = 0.05). The reproducibility of the developed sensor resulted better when a deposition time of 6 min was used (5.4 %, n = 3). The influence of different interferents on the analytical response has been studied, as well as their application in the determination of 4-ethylphenol in different wine samples.Authors would like to acknowledge funding obtained by Junta de Castilla y León (BU018G19) and Agencia Estatal de Investigación (PID2020-117095RB-I00)

Electrochemical devices for cholesterol detection

Cholesterol can be considered as a biomarker of illnesses such as heart and coronary artery diseases or arteriosclerosis. Therefore, the fast determination of its concentration in blood is interesting as a means of achieving an early diagnosis of these unhealthy conditions. Electrochemical sensors and biosensors have become a potential tool for selective and sensitive detection of this biomolecule, combining the analytical advantages of electrochemical techniques with the selective recognition features of modified electrodes. This review covers the different approaches carried out in the development of electrochemical sensors for cholesterol, differentiating between enzymatic biosensors and non-enzymatic systems, highlighting lab-on-a-chip devices. A description of the different modification procedures of the working electrode has been included and the role of the different functional materials used has been discussed

A Chronoamperometric Screen Printed Carbon Biosensor Based on Alkaline Phosphatase Inhibition for W(VI) Determination in Water, Using 2-Phospho-L-Ascorbic Acid Trisodium Salt as a Substrate

This paper presents a chronoamperometric method to determine tungsten in water using screen-printed carbon electrodes modified with gold nanoparticles and cross linked alkaline phosphatase immobilized in the working electrode. Enzymatic activity over 2-phospho-L-ascorbic acid trisodium salt, used as substrate, was affected by tungsten ions, which resulted in a decrease of chronoamperometric current, when a potential of 200 mV was applied on 10 mM of substrate in a Tris HCl buffer pH 8.00 and 0.36 M of KCl. Calibration curves for the electrochemical method validation, give a reproducibility of 5.2% (n = 3), a repeatability of 9.4% (n = 3) and a detection limit of 0.29 ± 0.01 μM. Enriched tap water, purified laboratory water and bottled drinking water, with a certified tungsten reference solution traceable to NIST, gave a recovery of 97.1%, 99.1% and 99.1% respectively (n = 4 in each case) and a dynamic range from 0.6 to 30 μM. This study was performed by means of a Lineweaver–Burk plot, showing a mixed kinetic inhibition.Vicerrectorìa de Investigación de la Universidad de Costa Rica (Project 804-B2-297), via Junta de Castilla y León (BU212A12-2), Ministerio de Ciencia e Innovación (MICINN) (TEC2009-12029) and MICINN and Fondo Europeo de Desarrollo Regional (FEDER) (INNPACTO SERIBIO 2011-2014)

A Disposable Alkaline Phosphatase-Based Biosensor for Vanadium Chronoamperometric Determination

A chronoamperometric method for vanadium ion determination, based on the inhibition of the enzyme alkaline phosphatase, is reported. Screen-printed carbon electrodes modified with gold nanoparticles were used as transducers for the immobilization of the enzyme. The enzymatic activity over 4-nitrophenyl phosphate sodium salt is affected by vanadium ions, which results in a decrease in the chronoamperometric current registered. The developed method has a detection limit of 0.39 ± 0.06 µM, a repeatability of 7.7% (n = 4) and a reproducibility of 8% (n = 3). A study of the possible interferences shows that the presence of Mo(VI), Cr(III), Ca(II) and W(VI), may affect vanadium determination at concentration higher than 1.0 mM. The method was successfully applied to the determination of vanadium in spiked tap waterResearch Vicerrectory of Costa Rica University (Project 804-B0-058) and Spanish Ministry of Science and Innovation (TEC-2009/12029). This work was supported by the Spanish Ministry of Science and Innovation (MICINN) 410 and the European Regional Development Fund (FEDER) (INNPACTO SERIBIO 2011-411 2014) and TEC2009-12029, as well as through Junta de Castilla y León (BU212A12-2)

Determination of aluminium using different techniques based on the Al(III)-morin complex

Three different methods for the determination of Al(III) in aqueous samples were compared. The different described procedures were based on the formation of the Al(III)-morin complex. UV–Vis spectrophotometry, spectrofluorimetry and differential pulse adsorptive stripping voltammetry (DPAdSV) techniques were compared under optimized experimental conditions. The DPAdSV method showed a better performance for the analysis of Al(III) in terms of capability of detection (70 nM) in comparison with the value obtained for UV–Vis spectrophotometric (300 nM) and spectrofluorimetic (110 nM) techniques. Thus, DPAdSV method was selected for the analysis of aluminium in river, tap and bottled water samples under the following optimized experimental conditions: pH = 4.4, deposition potential = +243 mV, deposition time = 210 s, giving satisfactory results

Determination of Antimony (III) in Real Samples by Anodic Stripping Voltammetry Using a Mercury Film Screen-Printed Electrode

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10−8 M. The linear range obtained was between 0.99 × 10−8 − 8.26 × 10−8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples

The impact of chemical differentiation of white dwarfs on thermonuclear supernovae

Gravitational settling of 22Ne in cooling white dwarfs can affect the outcome of thermonuclear supernovae. We investigate how the supernova energetics and nucleosynthesis are in turn influenced by this process. We use realistic chemical profiles derived from state-of-the-art white dwarf cooling sequences. The cooling sequences provide a link between the white dwarf chemical structure and the age of the supernova progenitor system. The cooling sequence of a 1 M_sun white dwarf was computed until freezing using an up-to-date stellar evolutionary code. We computed explosions of both Chandrasekhar mass and sub-Chandrasekhar mass white dwarfs, assuming spherical symmetry and neglecting convective mixing during the pre-supernova carbon simmering phase to maximize the effects of chemical separation. Neither gravitational settling of 22Ne nor chemical differentiation of 12C and 16O have an appreciable impact on the properties of Type Ia supernovae, unless there is a direct dependence of the flame properties (density of transition from deflagration to detonation) on the chemical composition. At a fixed transition density, the maximum variation in the supernova magnitude obtained from progenitors of different ages is ~0.06 magnitudes, and even assuming an unrealistically large diffusion coefficient of 22Ne it would be less than ~0.09 mag. However, if the transition density depends on the chemical composition (all other things being equal) the oldest SNIa can be as much as 0.4 magnitudes brighter than the youngest ones (in our models the age difference is 7.4 Gyr). In addition, our results show that 22Ne sedimentation cannot be invoked to account for the formation of a central core of stable neutron-rich Fe-group nuclei in the ejecta of sub-Chandrasekhar models, as required by observations of Type Ia supernovae.Comment: 8 pages, 8 figures, 3 tables, accepted for Astronomy and Astrophysics. Revised version with corrected typo