Fabricación y puesta a punto de una Nariz Electrónica Húmeda para la detección de gases y vapores

Tesis por compendioI begin this PhD thesis with an introductory chapter about electronic nose systems, where I describe the sensor system types, electronic nose types and the chemometric and measurement techniques employed in the development of the thesis. Next, I define the general and specific objectives of the thesis. In the following chapters I discuss the different aspects of the measuring device and the journal articles that served as motivation for its design. The first article is based on the proof of concept of the humid electronic nose prototype, whose design relies on the performance of voltammetric measurements. An array of four metallic working electrodes (iridium, rhodium, platinum and gold), housed inside a stainless steel cylinder that acts as counter electrode, and a reference electrode were all put in contact by a nylon mesh dampened with a sodium chloride aqueous solution. This system is used to differentiate between seven different samples by means of two statistical techniques: principal component analysis (PCA) and a type of neural network called self-organizing map (SOM). The results obtained were satisfactory, thus motivating how I approached the study performed in the following chapter. The second article contemplates a more complete study for a very specific application of the humid electronic nose system: the detection of nerve agent mimics. In this study, eight metals formed the array of working electrodes (iridium, rhodium, platinum, gold, silver, cobalt, copper and nickel) and the nylon mesh was dampened with sodium tetraborate. In order to enhance the results of the study, we designed two specific pulse patterns by analyzing the voltammograms (for the electrochemical characterization of the samples) of the eight electrodes on a diethyl cyanophosphate (DCNP) sample. We measured three nerve agent mimics and eight organophosphorous derivatives, in addition to sulphuric acid, ammonia, ethanol, acetonitrile and hexane. The PCA demonstrated that the proposed system was capable of distinguishing nerve agent mimics from the other organophosphorous derivatives. We also performed a partial least squares regression (PLS), which allowed DCNP to be quantified with a limit of detection of a few ppm. The third article is an in depth study about the reproducibility problems that usually arise in voltammetric measurements with the use of electronic tongues (and the electronic nose designed in this PhD thesis). The objective was to improve the reproducibility of the measurements performed with these systems by designing an electrochemical cell that warranted a homogenous distribution of the electric field and improved its limit of detection. Finally, an electronic measuring system was designed and is presented in chapter 4; it integrates voltammetry and potentiometry techniques. This system is composed of a PC application and an electronic measuring system, which can be used to test both measuring techniques on up to eight working electrodes. The PC application was designed to execute sequences of voltammetry and potentiometry tests, and to store and display the measured signals by means of a simple graphical user interface. The voltammetry measurements are based on the potentiostat measuring circuit, which allows 2 and 3 electrode measurements to be taken. To finish, I explain the conclusions drawn from both the general and specific objectives considered at the beginning of this thesis.La tesis comienza con un capítulo introductorio a los sistemas de nariz electrónica, donde se describen los tipos de sistemas sensores, los tipos de nariz electrónica y las técnicas quimiométricas y de medida usadas en el desarrollo de la tesis. A continuación, se describen los objetivos generales y específicos planteados. El diseño del equipo de medida se ha realizado teniendo en cuenta las conclusiones de las publicaciones en revistas de investigación que forman parte de esta tesis doctoral, las cuales se presentan en los tres capítulos siguientes. El primer artículo está fundamentado en la prueba de concepto del prototipo de nariz electrónica húmeda, en el que se presenta un diseño basado en ensayos voltamétricos. Para ello se utiliza un conjunto de cuatro electrodos de trabajo metálicos (iridio, rodio, platino y oro) encapsulados dentro de un cilindro de acero inoxidable, que actúa como contraelectrodo, y un electrodo de referencia con puente salino, todos ellos en contacto gracias a una membrana de nylon empapada en una solución acuosa de cloruro de sodio. Este sistema se usa para discriminar siete muestras distintas utilizando las técnicas de análisis de componentes principales (PCA) y un tipo de red neuronal, llamada mapa auto-organizado (SOM). Los resultados obtenidos son satisfactorios, por ello han motivado el planteamiento del estudio realizado en el siguiente capítulo. El segundo artículo plantea un estudio más completo para una aplicación muy específica del sistema de nariz electrónica húmeda: la detección de simulantes de agentes nerviosos. En este estudio el conjunto de electrodos de trabajo está formado por ocho electrodos de trabajo metálicos (iridio, rodio, platino, oro, plata, cobalto, cobre y níquel, la membrana de nylon está empapada esta vez en tetraborato de sodio. Para mejorar los resultados de este estudio se diseñan dos trenes de pulsos específicos mediante el análisis de los voltagramas (para la caracterización electroquímica de las muestras.) de los ocho electrodos sobre una muestra de dietil cianofosfato (DCNP). Las medidas se realizan sobre tres simulantes de agentes nerviosos y ocho derivados organofosforados, además de ácido sulfúrico, amonio, etanol, acetonitrilo y hexano. El PCA demuestra que el sistema propuesto es capaz de discriminar los principales simulantes de agentes nerviosos de los otros derivados organofosforados y otros interferentes potenciales. También se ha realizado una regresión por mínimos cuadrados parciales (PLS) que permite la cuantificación de DCNP hasta unos pocos ppm. El tercer artículo es un estudio en profundidad de los problemas de reproducibilidad que habitualmente se dan en las medidas voltamétricas con el uso de lenguas electrónicas (y la nariz electrónica objeto de esta tesis). El objetivo es mejorar la reproducibilidad de las medidas con estos sistemas a través de un diseño de la celda electroquímica que asegure una distribución homogénea del campo eléctrico, y para mejorar su límite de detección. Por último, en el capítulo número 4 se ha diseñado un sistema electrónico de medida que integra las técnicas de voltametría y potenciometría. Los elementos que integran este sistema son una aplicación de PC y un equipo electrónico de medida con el que se pueden realizar ensayos con las técnicas de medida mencionadas sobre hasta ocho electrodos de trabajo. La aplicación de PC está diseñada para la ejecución de secuencias de ensayos de potenciometría y voltametría, y para el almacenamiento y representación de las señales muestreadas mediante una interfaz gráfica de usuario simple. Las medidas de voltametría están basadas en el circuito de medida potenciostato, que permite implementar ensayos a 2 y 3 electrodos. Para finalizar, se exponen las conclusiones a los objetivos generales y específicos planteados al inicio de la tesis.La tesi comença amb un capítol introductori als sistemes de nas electrònic, on es descriuen els tipus de sistemes sensors, els tipus de nas electrònic i les tècniques quimiomètriques i de mesura utilitzades en el desenvolupament de esta tesi. A continuació, es descriuen els objectius generals y específics plantejats. El disseny de l'equip de mesura s'ha inspirat en les conclusions tretes de les publicacions en revistes d'investigació presentades en els tres capítols següents. El primer article està fonamentat en la prova de concepte del prototip de nas electrònic humit, en el que es presenta un disseny basat en assajos voltamètrics. Per a açò s'utilitza un conjunt de quatre elèctrodes de treball metàl·lics (Iridi, Rodi, Platí i Or) encapsulats en un cilindre d'acer inoxidable, que actua com a contraelectrode, i un elèctrode de referència amb pont salí, tots ells en contacte gràcies a una membrana de niló amerada amb una solució de clorur de sodi. Este sistema s'usa per a discriminar 7 mostres distintes utilitzant les tècniques d'anàlisi de components principals (PCA) i un tipus de xarxa neuronal, anomenada mapa auto-organitzat (SOM). Els resultats obtinguts son satisfactoris, fet que ha motivat el plantejament de l'estudi realitzat en el següent capítol. El segon article planteja un estudi més complet per a una aplicació molt específica del sistema de nas electrònic humit: la detecció de simulants d'agents nerviosos. En este estudi el conjunt d'elèctrodes està format per huit elèctrodes de treball metàl·lics (Iridi, Rodi, Platí, Or, Plata, Cobalt, Coure i Níquel), la membrana de niló està amerada esta vegada amb tetraborat de sodi. Per tal de millorar els resultats d'este estudi es dissenyen dos trens de polsos específics mitjançant l'anàlisi del voltagrames (per a la caracterització electroquímica de les mostres) dels huit elèctrodes sobre una mostra de dietil cioanofosfat (DCNP). Les mesures es realitzen sobre tres simultans d'agents nerviosos i huit derivats organofosforats, a més d'àcid sulfúric, amoni, etanol, acetonitril i hexà. El PCA demostra que el sistema proposat es capaç de discriminar els principals simulants d'agents nerviosos dels altres derivats organofosforats i altres interferents potencials. També s'ha realitzat una regressió per mínims quadrats parcials (PLS) que permet la quantificació de DCNP fins a unes poques ppm. El tercer article és un estudi en profunditat dels problemes de reproductibilitat que habitualment es donen en les mesures voltamètriques amb l'ús de llengües electròniques (y el nas electrònic objecte d'esta tesi). L'objectiu es millorar la reproductibilitat de les mesures amb estos sistemes mitjançant un disseny de la cel·la electroquímica que assegure una distribució homogènia del camp elèctric, i per a millorar el seu límit de detecció. Per últim, en el capítol número 4 s'ha utilitzat un sistema electrònic de mesura que integra les tècniques de voltametria i potenciometria. Els elements que integren este sistema son una aplicació de PC i un equip electrònic de mesura amb el que es poden realitzar assajos amb les tècniques de mesura mencionades sobre fins a huit elèctrodes de treball. La aplicació de PC està dissenyada per a l'execució de seqüències d'assajos de potenciometria i voltametria, i per a l'emmagatzematge de les senyals mesurades mitjançant un entorn d'usuari simple. Les mesures de voltametria estan basades en el circuit de mesura potenciostato, que permet implementar assajos a 2 i 3 elèctrodes. Per concloure, s'exposen les conclusions als objectius generals i específics plantejats al inici de la tesi.Bataller Prats, R. (2017). Fabricación y puesta a punto de una Nariz Electrónica Húmeda para la detección de gases y vapores [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/89083TESISCompendi

Monitoring honey adulteration with sugar syrups using an automatic pulse voltammetric electronic tongue

[EN] The new tendency to detect adulterated honey is the development of affordable analytical equipment that is in-line and manageable, enabling rapid on site screening. Therefore, the aim of this work was to apply an electronic tongue based on potential multistep pulse voltammetry, in combination with multivariate statistical techniques to detect and quantify syrup in honey. Pure monofloral honey (heather, orange blossom and sunflower), syrup (rice, barley and corn), and samples simulating adulterated honey with different percentages of syrup (2.5, 5, 10, 20 and 40) were evaluated. An automatic, electrochemical system for cleaning and polishing the electronic tongue sensors (Ir, Rh, Pt, Au) significantly improved the repeatability and accuracy of the measurements. PCA analysis showed that the proposed methodology is able to distinguish between types of pure honey and syrup, and their different levels of adulterants. A subsequent PLS analysis successfully predicted the level of the adulterants in each honey, achieving good correlations considering the adjusting parameters. The best results being for sunflower honey adulterated with corn syrup and heather honey with barley syrup (r2 ¿ 0.997), and heather with corn (r2 ¿ 0.994) whereas the weakest was found for heather honey adulterated with brown rice syrup (r2 ¿ 0.763) and orange blossom honey with corn syrup (r2 ¿ 0.879). The measurement system here proposed could be a very quick and effective option for the honey packaging sector with the finality of providing information about a characteristic as important as the adulteration of honey.This study forms part of the projects funded by the "Agencia Estatal de Investigacion" (AGL2016-77702-R) and by the "Generalitat Valenciana" (AICO/2015/104) of Spain, for which the authors are grateful.Sobrino-Gregorio, L.; Bataller Prats, R.; Soto Camino, J.; Escriche Roberto, MI. (2018). Monitoring honey adulteration with sugar syrups using an automatic pulse voltammetric electronic tongue. Food Control. 91:254-260. https://doi.org/10.1016/j.foodcont.2018.04.003S2542609

Using an automatic pulse voltammetric electronic tongue to verify the origin of honey from Spain, Honduras, and Mozambique

[EN] BACKGROUND: The growing need to classify the origin of honey in a simple way is leading to the development of affordable analytical equipment that is in-line and manageable, enabling rapid on-site screening. The aim of this work was therefore to evaluate whether an electronic tongue (made of four metallic electrodes: Ir, Rh, Pt, Au), based on potential multistep pulse voltammetry with electrochemical polishing, is able to differentiate between honey samples from Spain, Honduras, and Mozambique. RESULTS: It was demonstrated, for the first time, that automatic pulse voltammetry, in combination with principal component analysis (PCA) statistical analysis, was able to differentiate honey samples from these three countries. A partial least squares (PLS) analysis predicted the level of certain physicochemical parameters, the best results being for conductivity and moisture with correlation coefficients of 0.948 and 0.879, whereas the weakest correlation was for the sugars. CONCLUSION: The tool proposed in this study could be applied to identify the country origin of the three types of multifloral honey considered here. It also offers promising perspectives for expanding knowledge of the provenance of honey. All of this could be achieved when a comprehensive database with the information generated by this electronic tongue has been created. © 2019 Society of Chemical IndustryThis study forms part of the projects funded by the Ministerio de Economía y Competitividad, the Agencia Estatal de Investigación, and the Fondo Europeo de Desarrollo Regional (AGL2016-77702-R) and by the Programa ADSIDEO-cooperación 2016 of the Centro de Cooperación al Desarrollo de la Universitat Politècnica de València, Spain, for which the authors are grateful.Sobrino-Gregorio, L.; Tanleque-Alberto, F.; Bataller Prats, R.; Soto Camino, J.; Escriche Roberto, MI. (2020). Using an automatic pulse voltammetric electronic tongue to verify the origin of honey from Spain, Honduras, and Mozambique. Journal of the Science of Food and Agriculture. 100(1):212-217. https://doi.org/10.1002/jsfa.10022S2122171001Kaškonienė, V., & Venskutonis, P. R. (2010). Floral Markers in Honey of Various Botanical and Geographic Origins: A Review. Comprehensive Reviews in Food Science and Food Safety, 9(6), 620-634. doi:10.1111/j.1541-4337.2010.00130.xSoares, S., Amaral, J. S., Oliveira, M. B. P. P., & Mafra, I. (2017). A Comprehensive Review on the Main Honey Authentication Issues: Production and Origin. Comprehensive Reviews in Food Science and Food Safety, 16(5), 1072-1100. doi:10.1111/1541-4337.12278El Alami El Hassani, N., Tahri, K., Llobet, E., Bouchikhi, B., Errachid, A., Zine, N., & El Bari, N. (2018). Emerging approach for analytical characterization and geographical classification of Moroccan and French honeys by means of a voltammetric electronic tongue. Food Chemistry, 243, 36-42. doi:10.1016/j.foodchem.2017.09.067Escriche, I., Tanleque-Alberto, F., Visquert, M., & Oroian, M. (2017). Physicochemical and rheological characterization of honey from Mozambique. LWT, 86, 108-115. doi:10.1016/j.lwt.2017.07.053Bougrini, M., Tahri, K., Saidi, T., El Alami El Hassani, N., Bouchikhi, B., & El Bari, N. (2016). Classification of Honey According to Geographical and Botanical Origins and Detection of Its Adulteration Using Voltammetric Electronic Tongue. Food Analytical Methods, 9(8), 2161-2173. doi:10.1007/s12161-015-0393-2Benedetti, S., Mannino, S., Sabatini, A. G., & Marcazzan, G. L. (2004). Electronic nose and neural network use for the classification of honey. Apidologie, 35(4), 397-402. doi:10.1051/apido:2004025Dias, L. A., Peres, A. M., Vilas-Boas, M., Rocha, M. A., Estevinho, L., & Machado, A. A. S. C. (2008). An electronic tongue for honey classification. Microchimica Acta, 163(1-2), 97-102. doi:10.1007/s00604-007-0923-8Wei, Z., Wang, J., & Liao, W. (2009). Technique potential for classification of honey by electronic tongue. Journal of Food Engineering, 94(3-4), 260-266. doi:10.1016/j.jfoodeng.2009.03.016Major, N., Marković, K., Krpan, M., Šarić, G., Hruškar, M., & Vahčić, N. (2011). Rapid honey characterization and botanical classification by an electronic tongue. Talanta, 85(1), 569-574. doi:10.1016/j.talanta.2011.04.025Wei, Z., & Wang, J. (2011). Classification of monofloral honeys by voltammetric electronic tongue with chemometrics method. Electrochimica Acta, 56(13), 4907-4915. doi:10.1016/j.electacta.2011.02.065Escriche, I., Kadar, M., Domenech, E., & Gil-Sánchez, L. (2012). A potentiometric electronic tongue for the discrimination of honey according to the botanical origin. Comparison with traditional methodologies: Physicochemical parameters and volatile profile. Journal of Food Engineering, 109(3), 449-456. doi:10.1016/j.jfoodeng.2011.10.036Garcia-Breijo, E., Garrigues, J., Sanchez, L., & Laguarda-Miro, N. (2013). An Embedded Simplified Fuzzy ARTMAP Implemented on a Microcontroller for Food Classification. Sensors, 13(8), 10418-10429. doi:10.3390/s130810418Tiwari, K., Tudu, B., Bandyopadhyay, R., & Chatterjee, A. (2013). Identification of monofloral honey using voltammetric electronic tongue. Journal of Food Engineering, 117(2), 205-210. doi:10.1016/j.jfoodeng.2013.02.023Sousa, M. E. B. C., Dias, L. G., Veloso, A. C. A., Estevinho, L., Peres, A. M., & Machado, A. A. S. C. (2014). Practical procedure for discriminating monofloral honey with a broad pollen profile variability using an electronic tongue. Talanta, 128, 284-292. doi:10.1016/j.talanta.2014.05.004Juan-Borrás, M., Soto, J., Gil-Sánchez, L., Pascual-Maté, A., & Escriche, I. (2016). Antioxidant activity and physico-chemical parameters for the differentiation of honey using a potentiometric electronic tongue. Journal of the Science of Food and Agriculture, 97(7), 2215-2222. doi:10.1002/jsfa.8031Oroian, M., Paduret, S., & Ropciuc, S. (2018). Honey adulteration detection: voltammetric e-tongue versus official methods for physicochemical parameter determination. Journal of the Science of Food and Agriculture, 98(11), 4304-4311. doi:10.1002/jsfa.8956Palynological Database on line Available at:https://www.paldat.org/info[10 February 2019]Callejas MC Desarrollo de la norma técnica para polen en Honduras (2006). Available:https://bdigital.zamorano.edu/bitstream/11036/5380/1/AGI‐2006‐T005. pdf [10 February 2019].Schüler, L., & Hemp, A. (2016). Atlas of pollen and spores and their parent taxa of Mt Kilimanjaro and tropical East Africa. Quaternary International, 425, 301-386. doi:10.1016/j.quaint.2016.07.038Tanleque-Alberto, F., Juan-Borrás, M., & Escriche, I. (2019). 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H. D., & Shehata, M. G. (2015). Physicochemical characteristics of honey from different origins. Annals of Agricultural Sciences, 60(2), 279-287. doi:10.1016/j.aoas.2015.10.01

Macrocell Processes in Reinforced Concrete Structures

Corrosion of steel embedded in reinforced concrete is the phenomena that most affects the durability of this type of structures. The control and analysis of the rebars can help detect this problem beforehand, contributing to prevent costly repairs made when the damage is quite advanced. Currently, there are several techniques for measuring the corrosion rate of steel, but they have the disadvantage of being slow or requiring specialized tools. In addition, these techniques need direct connection to the rebars, so removing the concrete cover layer is necessary. This destructive technique is sometimes impossible to do because there are analysis zones which are inaccessible due to they are buried or submerged. Recently, using sensors embedded previously casting and external electrical connections let analyse the corrosion without using invasive techniques. This study presents the complementary technique of analysing macrocell currents in order to know the origin and direction of current in reinforcements. This technique requires less time and non-advanced material, only an ammeter and electrical connection to the rebars, executed before casting. In addition, this parameter provides information about the real corrosion of the different parts of the structure. In this study it is performed the laboratory analysis of this technique by the use of specimens containing one anode and one cathode inside them creating a macrocell. The influence of different environments on macrocell current intensities shall be studied and compared with other studied parameters as corrosion density

Integrated Sensor Network for Monitoring Steel Corrosion in Concrete Structures

The developed Integrated Sensor Network (ISN) allows a non-destructive monitoring of the rebar condition at different parts of the structure. The corrosion sensor allows the accurate determination of the corrosion rate (µm/year). Moreover, additional sensors are integrated in order to detect relevant changes in the concrete electrochemical condition. The ISN has been published as an international invention patent (reference number WO 2016/177929 A1). The system is based on an economic, simple, reliable and durable technology, which makes its implementation viable on new and repaired reinforced concrete structures (RCS). Therefore, it is also possible monitoring non-accessible parts such as deep foundations or submerged and buried zones. In any case, no technical personnel are needed because the acquisition, storage and transmission of data is autonomous. In this way, it is possible a remote corrosion assessment of several RCS. In addition, the system needs minimum maintenance works and shows low failure rates. The ISN has been installed for corrosion monitoring of a marine prestressed structure built with Formex®, an Ultra High Performance Fibre Reinforced Concrete (UHPFRC). Five zones of the structure are being monitored. After seven months of monitoring, the corrosion rate (CRATE) stands around 0.2 µm/year, lower than the corrosion rate of the conventional concrete specimens installed (0.5 µm/year). In any case, CRATE is under 1.16 µm/year, the threshold above which the corrosion begins to be considered significant

A study of the importance of the cell geometry in non-Faradaic systems. A new definition of the cell constant for conductivity measurement

A new definition for the electrochemical cell constant in conductivity measurements is presented in this paper. Electrochemical Impedance Spectroscopy and DC pulses measurements have been carried out in non-Faradaic conditions in order to evaluate the effects of the cell geometry. The results obtained demonstrate that conductivity measurements are affected not only by the electrodes surface and separation but also by the cross section of the electrochemical cell. In order to obtain a linear behavior of the resistance versus the distance between electrodes, the cross section of the cell should be equal to the electrodes surface. Differences between the cell cross section and the electrodes surface produce a heterogeneous distribution of the electric field that causes the non-linear behavior for low values of the electrodes separation. This study shows that the reproducibility in electronic tongue and humid electronic nose measurements can be improved by designing an electrochemical cell structure that warrants a homogeneous distribution of the electrical field, which results in a reduction of the detection threshold in these types of system.Financial support from the Spanish Government (projects MAT2012-38429-C04-04 and IPT-2012-0069-310000) is gratefully acknowledged. The pre-doctoral scholarship granted to Roman Bataller Prats within the program "Formacion de Personal Investigador (FPI) 2012" from Universitat Politecnica de Valencia is gratefully acknowledged.Bataller Prats, R.; Gandía Romero, JM.; García Breijo, E.; Alcañiz Fillol, M.; Soto Camino, J. (2015). A study of the importance of the cell geometry in non-Faradaic systems. A new definition of the cell constant for conductivity measurement. Electrochimica Acta. 153(20):263-272. https://doi.org/10.1016/j.electacta.2014.12.014S2632721532

A Novel Humid Electronic Nose Based on Voltammetry

We report herein the design, manufacture and use of a "humid electronic nose" prototype. Its operation is based on the use of voltammetric techniques, and it consists of an array of four working electrodes (i.e. Au, Pt, Ir and Rh) that were housed inside a homemade stainless steel cylinder and a fabric mesh made of nylon damped with a NaCl aqueous solution which was used as the supporting humid membrane. The "humid electronic nose" was tested for the discrimination of different samples displaying a different "aroma". The samples chosen involve aqueous solutions of different simple volatile samples (i.e. ammonia, acetone, acetic acid and 6-amino-1-hexanol) and different food samples (i.e. onion, coffee and Roquefort cheese). PCA studies from the response obtained by the "humid electronic nose" allowed discriminate between the different samples studied.Bataller Prats, R.; Campos Sánchez, I.; Alcañiz Fillol, M.; Gil Sánchez, L.; Martínez Mañez, R.; Soto Camino, J.; Vivancos, J. (2012). A Novel Humid Electronic Nose Based on Voltammetry. Procedia Engineering. 47:941-944. doi:10.1016/j.proeng.2012.09.301S9419444

A humid electronic nose based on pulse voltammetry: A proof-of-concept design

[EN] We report herein the design, manufacture and use of a "humid electronic nose" prototype based on voltammetric techniques. It consists of an array of four working electrodes (i.e., Au, Pt, Ir and Rh) housed inside a homemade stainless steel cylinder, in contact with a fabric mesh made of nylon damped with a NaCl aqueous solution, used as the supporting humid membrane. The "humid electronic nose" was tested for the discrimination of different samples displaying different volatile compounds. The samples chosen involve aqueous solutions of different simple volatile products (i.e., ammonia, acetone, acetic acid and 6-amino-1-hexanol) and different food samples (i.e., onion, coffee and Roquefort cheese). Under working conditions, the volatile compounds from the corresponding sample were generated in the measurement chamber and were partially dissolved in the damped nylon fabric, which was in contact with the set of electrodes. It was envisioned that provided different samples offer different vapours, the application of a suitable set of pulses to the electrodes will differentiate the samples. This proof-of-concept study employed a Large Amplitude Pulse Voltammetry (LAPV) waveform. The increment for the potential steps was of 200 mV and potentials ranged from +1 to -1 V with each pulse applied for 50 ms. PCA studies from the response obtained by the "humid electronic nose" discriminated the different samples studied. The neural network Self Organized Map (SOM) was also used to analyze the electrochemical data obtained from the "humid electronic nose". © 2013 Elsevier B.VThe financial support from the Spanish Government (project MAT2012-38429-C04) and the Generalitat Valenciana (Valencian Regional Government; projects PROMETEO/2009/016 and GV/2012/094); is gratefully acknowledged.Bataller Prats, R.; Campos Sánchez, I.; Alcañiz Fillol, M.; Gil Sánchez, L.; García Breijo, E.; Martínez Mañez, R.; Pascual Vidal, L.... (2013). A humid electronic nose based on pulse voltammetry: A proof-of-concept design. Sensors and Actuators B: Chemical. 186:666-673. https://doi.org/10.1016/j.snb.2013.06.033S66667318

Monitoring grape ripeness using a voltammetric electronic tongue

The use of a voltammetric electronic tongue as a tool to monitor grape ripeness is proposed herein. The electronic tongue consists of eight metallic electrodes housed inside a stainless steel cylinder. The study was carried out over a period of ca. 1 month (August 2012) on different grape varieties (Macabeo, Chardonnay, Pinot Noir, Cabernet Sauvignon, Shyrah, Merlot and Bobal) from various vineyards near Requena and Utiel (Valencia, Spain). Apart from the electrochemical studies, the physico-chemical parameters, such as, Total Acidity, pH and °Brix, were also determined in grapes. The PCA models, obtained using the physico-chemical or electrochemical data, showed variation of ripenesswith time.Moreover the studywas completed by using partial least squares (PLS) regression in an attempt to establish a correlation between the data collected from the electronic tongue and Total Acidity, pH and °Brix values. A good predictive modelwas obtained for the prediction of Total Acidity and °Brix. These results suggest the possibility of employing electronic tongues to monitor grape ripeness and of, therefore, evaluating the right time for harvesting.The financial support from the Spanish Government (project MAT2012-38429-C04-01) and the Generalitat Valenciana (Valencian Regional Government; project PROMETEO/2009/016) is gratefully acknowledged.Campos Sánchez, I.; Bataller Prats, R.; Armero, R.; Gandía Romero, JM.; Soto Camino, J.; Martínez Mañez, R.; Gil Sánchez, L. (2013). Monitoring grape ripeness using a voltammetric electronic tongue. Food Research International. 54(2):1369-1375. https://doi.org/10.1016/j.foodres.2013.10.011S1369137554

Glyphosate Detection by Means of a Voltammetric Electronic Tongue and Discrimination of Potential Interferents

A new electronic tongue to monitor the presence of glyphosate (a non-selective systemic herbicide) has been developed. It is based on pulse voltammetry and consists in an array of three working electrodes (Pt, Co and Cu) encapsulated on a methacrylate cylinder. The electrochemical response of the sensing array was characteristic of the presence of glyphosate in buffered water (phosphate buffer 0.1 mol·dm-3, pH 6.7). Rotating disc electrode (RDE) studies were carried out with Pt, Co and Cu electrodes in water at room temperature and at pH 6.7 using 0.1 mol·dm-3 of phosphate as a buffer. In the presence of glyphosate, the corrosion current of the Cu and Co electrodes increased significantly, probably due to the formation of Cu2+ or Co2+ complexes. The pulse array waveform for the voltammetric tongue was designed by taking into account some of the redox processes observed in the electrochemical studies. The PCA statistical analysis required four dimensions to explain 95% of variance. Moreover, a two-dimensional representation of the two principal components differentiated the water mixtures containing glyphosate. Furthermore, the PLS statistical analyses allowed the creation of a model to correlate the electrochemical response of the electrodes with glyphosate concentrations, even in the presence of potential interferents such as humic acids and Ca2+. The system offers a PLS prediction model for glyphosate detection with values of 098, -2.3 ¿ 10-5 and 0.94 for the slope, the intercept and the regression coefficient, respectively, which is in agreement with the good fit between the predicted and measured concentrations. The results suggest the feasibility of this system to help develop electronic tongues for glyphosate detection. © 2012 by the authors; licensee MDPI, Basel, Switzerland.Financial support from the Spanish Government (Project MAT2009-14564-C04-01 and PCI-Mediterraneo A/024590/09/A/ 03044/10), the Generalitat Valenciana (Project PROMETEO/2009/016), the UPV (project PAID-05-10) and its Centre de Cooperacio al Desenvolupament (Programa ADSIDEO-COOPERACIO 2010) is gratefully acknowledged.Bataller Prats, R.; Campos Sánchez, I.; Laguarda Miró, N.; Alcañiz Fillol, M.; Soto Camino, J.; Martínez Mañez, R.; Gil Sánchez, L.... (2012). Glyphosate Detection by Means of a Voltammetric Electronic Tongue and Discrimination of Potential Interferents. Sensors. 12:17553-17568. https://doi.org/10.3390/s121217553S175531756812Sierra, E. V., Méndez, M. A., Sarria, V. M., & Cortés, M. T. (2008). Electrooxidación de glifosato sobre electrodos de níquel y cobre. 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