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

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

Molecularly imprinted polypyrrole based electrochemical sensor for selective determination of 4-ethylphenol

This work describes the development of an electrochemical sensor based on a molecularly imprinted polymer (MIP) for sensitive and selective determination of 4-ethylphenol in wine. The sensor has been built by means of the electrosynthesis of the MIP on a glassy carbon electrode surface using cyclic voltammetry. The electropolymerization has been performed in the presence of 4-ethylphenol and pyrrole as template molecule and functional monomer, respectively. The influence of the molar ratios of template molecules to functional pyrrole monomers and the time needed to remove the template have been optimized taking into account the differential pulse voltammetric response of 4-ethylphenol. Under the optimal experimental conditions the developed MIP/GCE sensor shows good capability of detection (0.2 μM, α = β = 0.05) and reproducibility (3.0%) in the concentration range from 0.2 to 34.8 μM. The influence of possible interfering species in the analytical response has been studied and the sensor has successfully been applied to the determination of 4-ethylphenol in different wine samples.Junta de Castilla y León (BU018G19

La interdisciplinariedad y el itinerario curricular elegido por el estudiante, ejes fundamentales para desarrollar competencias curriculares en Química

Póster presentado en: V Jornadas de Innovación Docente de la UBU, Burgos, 21-22 de octubre de 2010, organizadas por el Instituto de Formación e Innovación Educativa-IFIE de la Universidad de Burgo

Recent Trends in Enzyme-Based Electrosensing Devices Modified with Nanomaterials

Enzyme-based electrochemical biosensors are analytical devices with great potential in various fields, thanks to their specificity, high sensitivity, and the possibility of automation and miniaturization. The analytical performance of these electrochemical devices can be remarkably improved by the employing of advanced nanomaterials due to the important features of these materials, including great effectiveness in electron transfer related to its high surface area and conductivity. This chapter reports the recent applications of different enzymatic biosensors based on the modification of the working electrode with nanomaterials, including fullerenes, graphene, carbon nanotubes (CNTs), carbon and graphene quantum dots (QDs), metallic nanoparticles (NPs), and inorganic QDs. The reported devices are categorized according to the target biomolecule, and their description has considered not only the nanomaterial used but also the type of electronic transfer that takes place (direct or mediated) as well as the enzymatic mechanism involved

Electrochemical sensors for the determination of 4-ethylguaiacol in wine

The development of an electrochemical procedure for the determination of 4-ethylguaiacol and its application to wine analysis is described. Modified screen-printed carbon electrodes (SPCEs) with fullerene C60 (C60) have been shown to be efficient in this kind of analysis. The developed activated C60/SPCEs (AC60/SPCEs) were adequate for the determination of 4-ethylguaicol, showing a linear range from 200 to 1000 µg/L, a reproducibility of 7.6% and a capability of detection (CCβ) value of 200 µg/L, under optimized conditions. The selectivity of the AC60/SPCE sensors was evaluated in the presence of possibly interfering compounds, and their practical applicability was demonstrated in the analysis of different wine samples obtaining recoveries ranging from 96 to 106%.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research was supported by the Agencia Estatal de Investigación/Ministerio de Ciencia e Innovación under the project code PID2020-117095RB-I00

Current state of electrochemical sensors in wine analysis for early diagnosis

The assurance of the quality of a wine, both from the point of view of tasting and food safety, and its compliance with current regulations have led to the development of electrochemical sensors for the analysis of several analytes during the last five years. On one hand, the content of glucose, alcohol, acetaldehyde, organic acids, phenolic compounds, sulphur dioxide, mercaptans, biogenic amines, food preservatives and some yeast can affect the stability and the organoleptic properties. On the other hand, some of them can cause harmful effects on the health of the consumer. So, early diagnosis is extremely important in wine samples. Enzymatic and non-enzymatic electrochemical sensors, which generally uses nanostructured materials or chemically modified electrodes to enhance both sensitivity and selectivity, have been reported with this aim. The ability of these types of sensors to be miniaturized and their ease of use make them ideal candidates for point-of-care devices.Funding from Agencia Estatal de Investigación/Ministerio de Ciencia e Innovación (PID2020-117095RB-I00/AEI/10.13039/501100011033)

Unequal effect of ethanol–water on the stability of ct-DNA, poly[(dA–dT)]2 and poly(rA)·poly(rU). Thermophysical properties

Ethanol affects unequally the thermal stability of DNA and RNA. It stabilizes RNA, while destabilizing DNA. The variation of the relative viscosity (η/η0) of [poly(dA–dT)]2 with temperature unveils transitions close to the respective denaturation temperature, calculated spectrophotometrically and calorimetrically. From the raw data densities and speeds of sound, the volumetric observables were calculated. In all cases studied, a change in sign from low to high ethanol content occurred for both partial molar volume (ϕV) and partial molar adiabatic compressibility (ϕKS). The minima, close to 10%, should correspond to the highest solvation and the maxima, close to 30%, to the lowest solvation. For 40–50% ethanol, the solvation increases again. The complex structure of ethanol–water, for which changes are observed in regions close to such critical concentrations, justifies the observed behaviour. The variation of ϕV and ϕKS was sharper for RNA compared with respect to DNA, indicating that the solvation sequence is poly(rA)·poly(rU) < ct-DNA < [poly(dA–dT)]2.The financial support by Junta de Castilla y León (Fondo Social Europeo, project BU-299A12-1) and Obra Social “la Caixa” project OSLC-2012-007, Spain, is gratefully acknowledged

Preferential solvation and mixing behaviour of the essential oil 1,8-cineole with short–chain hydrocarbons

This work deals with the structure and solvation ability of the binary mixtures of the essential oil 1,8-cineole with n-hexane, n-octane and n-decane. The relevant derived properties excess isobaric heat capacity, molar excess volume, mixing viscosity, excess isentropic compressibility and activation Gibbs free energy were calculated from the measurements of the respective thermophysical properties carried out at atmospheric pressure in a wide range of temperatures. The data obtained were correlated with the solvent composition over the whole range and interpreted in terms of structural features and molecular interactions. The observed effect of temperature and the underlying interactions stress the propensity of the pure hydrocarbons for packing and folding. The solvation ability of the mixed solvents was assessed with the preferential solvation model, using the solvatochromic probes 2-nitroanisole and 4-nitroaniline, and the Hansen solubility parameters as well, the mixtures displaying stronger solvation power than the pure constituents.The financial support of the projects OSLC-2012-007 Obra Social “la Caixa” and CTQ 2014-58812-C2-2-R MINECO, Spain, is gratefully acknowledged