Caracterización estructural y electroquímica de materiales Sonogel-Carbono modificados y su empleo como sensores electroquímicos selectivos

En esta Tesis Doctoral se ha abordado la caracterización estructural y electroquímica de los nuevos materiales Sonogel-Carbono, desarrollados y patentados por nuestro grupo de investigación, y de sus modificaciones. El planteamiento y la finidad del trabajo se han dirigido hacie el conocimiento de la estructura y de la superficie de los materiales, con el fin de poder comprender la utilidad y el comportamiento de lo sensores electroquímicos desarrollados. Para ello se han empleado diversas técnicas de análisis estructural, como son: Microscopia Electrónica de Barrido y de Transmisión (SEM y TEM), Microscopia de Fuera Atómica (AFM), Espectrocopía de Energía Dispersiva de Rayos X (EDS), Espectroscopia Infrarroja con Transformada de Fourier (FTIR) y Difracción de Rayos X (XDR), además de técnicas voltamperométricas para evaluar el comportamiento como sensor del material fabricado, entre las que destacamos la Voltamperometría Diferencial de Impulsos (DPV) y la Voltamperometría Cíclica (CV). Se ha investigado el comportamiento de los materiales, cuando cambiamos alguno de los parámetros del proceso de fabricación de los materiales, como es el cambio del tipo de grafito, del que se han probado tres tipos distintos, con diferentes tamaños de partícula, demostrando que es un parñametro que influye de manera notable en la estructuración y estabilidad de los materiales Sonogel-Carbono. También se ha estudiado el comportamiento de los electrodos fabricados con estas modificaciones, usados tanto como sistema directo de medida para especies orgánicas, como el 4-cloro-3-metilfenol, así como su empleo como soporte base para la incorporación de modificantes, como son el Polietilenglicol (PEG) y el C18, modificantes que han sido utilizados para aplicaciones electroanalíticas con el material base Sonogel-Carbono, y que, en esta Tesis, se han caracterizado estructural y superficialmente con las técnicas antes mencionadas. También se han introducido diversas tioureas pertenecientes a la familia de las 1-furoiltioureas, para la determinación de especies inorgánicas como por ejemplo el Cd (II). En ambos conjuntos de estudios, los resultados obtenidos se consideran satisfactorios. Se logra renovar efectivamente la superficie activa del electrodo mediante tratamiento electroquimico. También se ha llevado a cabo una caracterización de superficie del electrodo Sonogel-Carbono y Sonogel-Carbono modificado

Acidification of musts in warm regions with tartaric acid and calcium sulfate at industrial scale

Acidification of musts is necessary in warm areas where high temperatures during ripening accelerate breathing combustion of tartaric acid and, in particular, malic acid in the berries. L(+) tartaric acid, L(-) or D,L malic acid and lactic acids are the only chemical acidifiers authorized by the OIV and European Community regulations. The use of calcium sulfate (gypsum: CaSO4·2H2O) is also authorized in the European Community as a complementary acidifier in generous and generous liquor wines from Spain (a practice known as plastering), provided that the residual sulfate content in the wine does not exceed 2.5 g/L expressed as potassium sulfate. However, this practice is not yet approved by OIV. To predict the effect on pH of different acidifiers, several chemical modeling approaches have been described in the literature, in particular a simplified model where the acidity of wine is considered to be due to a monoprotic acid. The aim of this work is to verify this model at pilot and industrial scale in the acidification of musts with tartaric and calcium sulfate, added either individually and in combination, using doses up to 3 g/L and to study the modifications that these practices produce on the compositions of the resulting wines. This work supplies useful information to study this practice in OIV in order to consider its approval

A novel magnetic molecularly imprinted polymer for selective extraction and determination of quercetin in plant samples

Molecularly imprinted polymers that mimic the binding mechanism of antibodies and their antigens exhibit several advantages, such as fast synthesis, low cost, high stability, and allow to overcome the ethical issues associated with antibody farming in animals. Herein, a novel strategy combining the magnetic molecularly imprinted polymer (MMIP) as an artificial antibody with a fluorescence procedure for the detection of quercetin in plant samples was designed. The MMIP was synthesized via a radical polymerization process to recognize specific functional groups of quercetin using a green technique based on high energy ultrasound irradiation. The developed MMIP was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning/transmission electron microscopy, and thermal gravimetric analysis, which confirmed the successful preparation of MMIP. The adsorption capacity and selectivity of the MMIP for quercetin and other interferents analogous were performed. The MMIP was applied in the solid-phase extraction (SPE) technique as a selective sorbent for the sample preparation. Besides, a sensitive fluorometric method for the quantitation of quercetin was developed. A linear response was obtained within the concentration of 0.005e1.25 mg mL 1 of quercetin. The limit of detection and quantitation were 1.1 ng mL 1 and 3.7 ng mL 1, respectively. The average recoveries for quercetin were between 92.2% and 104.7% with an RSD less than 5.06% in spiked orange juice and tea extract samples. Furthermore, the developed procedure was successfully combined with a new paperbased analytical device for on-site smartphone analysis of quercetin. © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Química analítica para ingenieros técnicos industriales (Química industrial)

El siguiente Curso OCW se dirige especialmente a alumnos matriculados en la titulación de Ingeniería Técnica Industrial – Especialidad en Química Industrial que han de cursar la asignatura de Química Analítica. Esta asignatura, tal y como se orienta en el presente Curso OCW, se imparte desde el curso 2007/2008 hasta la actualidad en la Escuela Politécnica Superior de Algeciras de la Universidad de Cádiz

Computational approach and ultrasound Probe-Assisted synthesis of magnetic molecularly imprinted polymer for the electrochemical detection of bisphenol A

A new theoretical approach based on density functional theory was developed to find the most suitable monomer and pomgen solvent to design a specific molecularly imprinted polymer (MIP) for bisphenol-A (BPA). Various theoretical investigations were carried out including HOMO and LUMO calculation, molecular electrostatic potential of the BPA-monomer interactions, and selection of the optimal monomer and porogen solvent using binding energies of BPA-monomer. Besides, counterpoise correction was used to avoid the problem of basis set superposition error. The theoretical results demonstrated that among virtual monomers, methacrylic acid and acrylamide showed good affinity towards BPA. The optimization of solvents was done using the polarizable continuum model and it was found that acetone was the most appropriate solvent. According to the obtained theoretical approach results, magnetic MIP (magMIP) was prepared using a high-power ultrasound probe. Scanning/transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction were used to characterize the as-prepared magMIP. Adsorption behavior was explained by Sips and pseudo-second-order models for isotherm and kinetic studies, respectively. Furthermore, magMIP showed favorable adsorption selectivity for BPA over other phenolic compounds. Finally, the developed magMIP was successfully used as a sorbent in solid-phase extraction combined with an electrochemical sensor for the detection of BPA. The obtained limit of detection was 66 nM and the recovery values in tap water sample were 104 and 105.5% for 2 and 10 mu M, respectively, with RSD values lower than 5 % (n = 3).Abderrahman Lamaoui gratefully acknowledges financial support from Erasmus + KA107 (EU) Program of the University of Cadiz (Spain) , through 'Servicio Espanol para la Internacionalizacion de la Educacion' (SEPIE) . The authors also acknowledge Junta de Andalucia (PAIDI2020) and the Institute of Research on Electron Microscopy and Materials (IMEYMAT, projects: APPLIED-SENS and POLYBIOSENS) for providing research funds. Besides, we also thank 'Programa de fomento e impulso de la investigacion y de la transferencia de la Universidad de Cadiz 2020-2021' for the funds given through the project PR2020-013 (Proyectos de Investigacion-Puente 2020) . Finally, the authors thank Area de Sistemas de Informacion (Supercomputacion) at UCA for the computational facilities (supercomputer) and Prof. Dr. David ZorrillaCuenca for his help with the calculation using the supercomputer, and Ms. Maria del Rocio Gonzalez-Moya (Technician of the University of Cadiz, Spain) for her assistance in performing the TGA analyses

Fast Analysis of Caffeic Acid-Related Molecules in Instant Coffee by Reusable Sonogel–Carbon Electrodes

Reusable Sonogel–Carbon electrodes containing carbon black (SNGC-CB) have been used for the electrochemical analysis of caffeic acid (CA) in real matrices. Measurements were firstly performed in standard solutions, in which SNGC-CB electrodes allowed the electrochemical determination of CA with high sensitivity and low limit of detection, equal to 0.76 μM. The presence of CB nanostructures in the formulation led to improved performances with respect to pristine SNGC electrodes. Then, measurements were performed in four instant coffees of different brands. A comparison between the results obtained by electrochemical, chromatographic and spectroscopic methods showed that SBGC-CB electrodes represent a simple and economic tool for the rapid assessment of caffeic acid-related molecules in instant coffees

E-Tongues/Noses Based on Conducting Polymers and Composite Materials: Expanding the Possibilities in Complex Analytical Sensing

Conducting polymers (CPs) are extensively studied due to their high versatility and electrical properties, as well as their high environmental stability. Based on the above, their applications as electronic devices are promoted and constitute an interesting matter of research. This review summa- rizes their application in common electronic devices and their implementation in electronic tongues and noses systems (E-tongues and E-noses, respectively). The monitoring of diverse factors with these devices by multivariate calibration methods for different applications is also included. Lastly, a critical discussion about the enclosed analytical potential of several conducting polymer-based devices in electronic systems reported in literature will be offered

Simultaneous Detection of Glucose and Fructose in Synthetic Musts by Multivariate Analysis of Silica-Based Amperometric Sensor Signals

Silica-based electrodes which permanently include a graphite/Au nanoparticles composite were tested for non-enzymatic detection of glucose and fructose. The composite material showed an effective electrocatalytic activity, to achieve the oxidation of the two analytes at quite low potential values and with good linearity. Reduced surface passivation was observed even in presence of organic species normally constituting real samples. Electrochemical responses were systematically recorded in cyclic voltammetry and differential pulse voltammetry by analysing 99 solutions containing glucose and fructose at different concentration values. The analysed samples consisted both in glucose and fructose aqueous solutions at pH 12 and in solutions of synthetic musts of red grapes, to test the feasibility of the approach in a real frame. Multivariate exploratory analyses of the electrochemical signals were performed using the Principal Component Analysis (PCA). This gave evidence of the effectiveness of the chemometric approach to study the electrochemical sensor responses. Thanks to PCA, it was possible to highlight the different contributions of glucose and fructose to the voltammetric signal, allowing their selective determination.This research received funding from the University of Cadiz through the 'Contratos Puente 2015' postdoctoral program and from the University of Modena and Reggio Emilia (Italy) through FAR 2014

Aplicación de tecnologías verdes a la síntesis de polímeros impresos molecularmente.

Resumen del proyecto de líneas prioritarias "Aplicación de tecnologías verdes a la síntesis de polímeros impresos molecularmente" del IMEYMAT

Rapid extraction and detection of ellagic acid in plant samples using a selective magnetic molecularly imprinted polymer coupled to a fluorescence method

A remarkable growth was noticed in the development of molecularly imprinted polymers (MIPs), which have used as efficient synthetic antibodies that contain selective cavities to the target molecule. Hereunder, a novel strategy using MIP as a sorbent in solid-phase extraction was coupled to a fluorescence method for ellagic acid (EA) purification and immediate detection. The synthesis of magnetic-MIP (MMIP) using a rapid and green ultrasound technology was assessed by central composite design to determine the optimal polymerization conditions for a high-imprinting polymer. The MMIP was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning/transmission electron microscopy, which accurately confirmed the functional, magnetic, and morphological features of MMIP. The prepared MMIP was demonstrated to be selective for EA compared to many similar phenols. The spectrofluorometric method showed a linear range from 0.05 to 2 μg·mL−1 of EA, and the limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.02 μg·mL−1, respectively. Besides, the novel proposed smartphone method using the ultraviolet lamp as the excitation source presented a linear range from 0.2 to 4 μg·mL−1, a LOQ of 0.2 μg·mL−1, and a LOD of 0.07 μg.mL−1. The proposed strategy revealed high efficiency in the extraction and detection of EA in grape, redberry, and green tea. Effectively, the calculated recoveries were ranging from 80 to 102% with low values of relative standard deviation ([removed]10 página