Simultaneous titration of ternary mixtures of Pb(II), Cd(II) and Cu(II) with potentiometric electronic tongue detection

An automatic titration method is reported to resolve ternary mixtures of transition metals (Pb²⁺,Cd²⁺ and Cu²⁺) employing electronic tongue detection and a reduced number of pre-defined additions of EDTA titrant. Sensors used were PVC membrane selective electrodes with generic response to heavy-metals, plus an artificial neural network response model. Detection limits obtained were ca. 1 mg L¯¹ for the three target ions and reproducibilities 3.0 % for Pb²⁺, 4.1 % for Cd²⁺ and 5.2 % for Cu²⁺. The system was applied to contaminated soil samples and high accuracy was obtained for the determination of Pb²⁺. In the determination Cd²⁺ and Cu²⁺,sample matrix showed a significant effect

Flexible carbon electrodes for electrochemical detection of bisphenol-a, hydroquinone and catechol in water samples

This research was funded by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), grant number (Proc. 2018/22214-6 and 2016/01919-6); by Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brazil (CAPES), grant number 88887.375050/2019-00 and 88887.375049/2019-00; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico-CNPq, grant number 153855/2018-5 and 423952/2018-8 and INEO (Brazil).The detection of pollutant traces in the public water supply and aquifers is essential for the safety of the population. In this article, we demonstrate that a simple electrochemical procedure in acidic solution can be employed for enhancing the sensitivity of flexible screen-printed carbon electrodes (SPEs) to detect bisphenol-A (BPA), hydroquinone, and catechol, simultaneously. The SPEs were pretreated electrochemically in a H2 SO4 solution, which did not affect their morphology, yielding high current signals with well separated oxidation peaks. The sensitivity values were 0.28, 0.230, and 0.056 µA L µmol−1 with detection limits of 0.12, 0.82, and 0.95 µmol L−1 for hydroquinone, catechol, and BPA, respectively. The sensors were reproducible and selective for detecting BPA in plastic cups, and with adequate specificity not to be affected by interferents from water samples. The simple, inexpensive, and flexible SPE may thus be used to detect emerging pollutants and monitor the water quality.publishersversionpublishe

Sustainable smart tags with two‐step verification for anticounterfeiting triggered by the photothermal response of upconverting nanoparticles

No abstract available.This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020) and Shape of Water (PTDC/NAN-PRO/3881/2020) financed by Portuguese funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. F.E.M. acknowledges the funding received from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 823941. The support of the European Union’s Horizon 2020 FET Open program under grant agreement no. 801305 (NanoTBTech) is also acknowledged. R.R.S. acknowledges the financial support from the Brazilian agency FAPESP (process no. 16/06612-6).publishe

Potentiometric Electronic Tongue to Resolve Mixtures of Sulfide and Perchlorate Anions

This work describes the use of an array of potentiometric sensors and an artificial neural network response model to determine perchlorate and sulfide ions in polluted waters, by what is known as an electronic tongue. Sensors used have been all-solid-state PVC membrane selective electrodes, where their ionophores were different metal-phtalocyanine complexes with specific and anion generic responses. The study case illustrates the potential use of electronic tongues in the quantification of mixtures when interfering effects need to be counterbalanced: relative errors in determination of individual ions can be decreased typically from 25% to less than 5%, if compared to the use of a single proposed ion-selective electrode

Desarrollo de lenguas electrónicas potenciométricas para la determinación simultánea de metales pesados en muestras ambientales

La presente tesis doctoral está enfocada al desarrollo de herramientas analíticas avanzadas, basadas en lenguas electrónicas potenciométricas y redes neuronales artificiales, para la determinación de trazas de metales de transición, específicamente Cu(II), Cd(II), Pb(II) y Zn(II) en muestras ambientales. En la búsqueda de nuevos elementos de reconocimiento, se sintetizaron y caracterizaron dos nuevos derivados de bis-tioureas, que fueron empleados como ionóforos en electrodos selectivos a plomo. Los dos electrodos obtenidos fueron caracterizados completamente y se obtuvieron muy buenos parámetros analíticos. La aplicabilidad de los dos dispositivos construidos se comprobó en la determinación de plomo en muestras de suelos, los resultados obtenidos se contrastaron de forma satisfactoria frente a un método de referencia (ICP-MS). Con los electrodos construidos previamente y con otros formulados mediante membranas comerciales, se conformaron las matrices de sensores que fueron empleadas en diversas aplicaciones. En la primera de ellas, se desarrolló una lengua electrónica potenciométrica para la determinación simultánea de Cu2+, Cd2+, Pb2+ y Zn2+ a nivel de trazas en muestras de suelos. El modelo fue construido mediante redes neuronales artificiales, con muy buen ajuste y habilidad predictiva. La estrategia propuesta fue aplicada a la determinación de los 4 analitos en muestras de suelos. Los resultados obtenidos se compararon con un método de referencia (FAAS). En la segunda aplicación se empleó una lengua electrónica como método de detección del punto final en un sistema de valoración complexométrica, para resolver mezclas ternarias de metales de transición. Con el objetivo de disminuir el tiempo de análisis, se utilizó una metodología de valoración con un número reducido de adiciones fijas de agente valorante. La información multivariada obtenida fue tratada con redes neuronales artificiales, y se pudo determinar simultáneamente en muestras de suelos dopadas el contenido de Cu2+, Cd2+ y Pb2+, lo que representa un aporte considerable, ya que estas aplicaciones son prácticamente imposibles con las metodologías convencionales de valoración. Las aplicaciones posteriores estuvieron enfocadas al desarrollo de un sistema automatizado, basado en lenguas electrónicas y análisis por inyección en flujo; para la monitorización de procesos de biosorción de mezclas de metales de transición en raspo de uva, residual de la industria vinícola. Se emplearon diferentes lenguas electrónicas como método de detección y se lograron monitorizar satisfactoriamente diferentes mezclas, de dos, tres y cuatro componentes. Con la información adquirida, se obtuvieron los principales parámetros termodinámicos de los procesos estudiados, la capacidad de sorción (q0), la capacidad de sorción del volumen del lecho (N0) y el tiempo requerido para alcanzar el 50 % del sorbato (r). Estos fueron comparados con los modelos teóricos de Thomas, Yoon-Nelson y BDST, en todos los casos se obtuvo un buen ajuste. También se determinó el orden de selectividad del raspo de uva (biosorbente) hacia los diferentes metales estudiados y el mecanismo predominante y responsable de la biosorción fue el intercambio iónico.This thesis is focused on the development of advanced analytical tools based on potentiometric electronic tongues and artificial neural networks, for the determination of transition metal traces, particularly Cu(II), Cd(II), Pb(II) and Zn(II) in environmental samples. In the search for new recognition elements, two new bis-thiourea derivatives were synthesized and characterized, which were used as ionophores in lead selective electrodes. The electrodes obtained were fully characterized and yielded very good analytical parameters. The applicability of the two devices constructed was verified in the determination of lead in soil samples, the results obtained were compared successfully against a reference method (ICP-MS). Using these previously constructed electrodes in concert with additional electrodes exploiting commercially fabricated sensory elements, a sensor array was formed and thus used in various applications. The first of these applications was a potentiometric electronic tongue for the simultaneous determination of Cu2+, Cd2+, Pb2+ and Zn2+ at trace levels in soil samples. The model was constructed with the use of artificial neural networks and exhibited a very good fit and predictive ability. The proposed strategy was applied to the determination of these 4 analytes in soil samples. The results were also compared with a reference method (FAAS). In the second application, the electronic tongue was employed as end point detection method in titration system, to resolve ternary mixtures of transition metals. In order to reduce the analysis time, a complexometric fixed volume titration methodology was used. The multivariate information obtained was treated with artificial neural networks, and the Cu2+, Cd2+ and Pb2+ volumes were simultaneously determined in soil spiked samples, which represents a significant contribution to the state-of-the-art, as these applications are virtually impossible to achieve with conventional titration methodologies. Subsequent applications were focused on the development of an automated system based on electronic tongues and flow injection analysis, for the monitoring of biosorption processes of mixtures of transition metals in grape stalk, wine industry waste. Several electronic tongues were used as a detection method, and achieved the satisfactorily monitoring of different mixtures of two, three and four components. Using the obtained information, the main thermodynamic parameters of the studied processes were successfully determined; these were the sorption capacity (q0), the sorption capacity of the bed volume (N0) and the time required to reach 50% of the sorbate (r). These were then compared to theoretical models of Thomas, Yoon-Nelson and BDST in all cases a good fit was achieved. The mechanism responsible for biosorption, ion exchange, and the order of selectivity grape stalk (biosorbent) towards different metals studied was also determined

Simultaneous titration of ternary mixtures of Pb(II), Cd(II) and Cu(II) with potentiometric electronic tongue detection

An automatic titration method is reported to resolve ternary mixtures of transition metals (Pb²⁺,Cd²⁺ and Cu²⁺) employing electronic tongue detection and a reduced number of pre-defined additions of EDTA titrant. Sensors used were PVC membrane selective electrodes with generic response to heavy-metals, plus an artificial neural network response model. Detection limits obtained were ca. 1 mg L¯¹ for the three target ions and reproducibilities 3.0 % for Pb²⁺, 4.1 % for Cd²⁺ and 5.2 % for Cu²⁺. The system was applied to contaminated soil samples and high accuracy was obtained for the determination of Pb²⁺. In the determination Cd²⁺ and Cu²⁺,sample matrix showed a significant effect

Desarrollo de lenguas electrónicas potenciométricas para la determinación simultánea de metales pesados en muestras ambientales

La presente tesis doctoral está enfocada al desarrollo de herramientas analíticas avanzadas, basadas en lenguas electrónicas potenciométricas y redes neuronales artificiales, para la determinación de trazas de metales de transición, específicamente Cu(II), Cd(II), Pb(II) y Zn(II) en muestras ambientales. En la búsqueda de nuevos elementos de reconocimiento, se sintetizaron y caracterizaron dos nuevos derivados de bis-tioureas, que fueron empleados como ionóforos en electrodos selectivos a plomo. Los dos electrodos obtenidos fueron caracterizados completamente y se obtuvieron muy buenos parámetros analíticos. La aplicabilidad de los dos dispositivos construidos se comprobó en la determinación de plomo en muestras de suelos, los resultados obtenidos se contrastaron de forma satisfactoria frente a un método de referencia (ICP-MS). Con los electrodos construidos previamente y con otros formulados mediante membranas comerciales, se conformaron las matrices de sensores que fueron empleadas en diversas aplicaciones. En la primera de ellas, se desarrolló una lengua electrónica potenciométrica para la determinación simultánea de Cu2+, Cd2+, Pb2+ y Zn2+ a nivel de trazas en muestras de suelos. El modelo fue construido mediante redes neuronales artificiales, con muy buen ajuste y habilidad predictiva. La estrategia propuesta fue aplicada a la determinación de los 4 analitos en muestras de suelos. Los resultados obtenidos se compararon con un método de referencia (F13S). En la segunda aplicación se empleó una lengua electrónica como método de detección del punto final en un sistema de valoración complexométrica, para resolver mezclas ternarias de metales de transición. Con el objetivo de disminuir el tiempo de análisis, se utilizó una metodología de valoración con un número reducido de adiciones fijas de agente valorante. La información multivariada obtenida fue tratada con redes neuronales artificiales, y se pudo determinar simultáneamente en muestras de suelos dopadas el contenido de Cu2+, Cd2+ y Pb2+, lo que representa un aporte considerable, ya que estas aplicaciones son prácticamente imposibles con las metodologías convencionales de valoración. Las aplicaciones posteriores estuvieron enfocadas al desarrollo de un sistema automatizado, basado en lenguas electrónicas y análisis por inyección en flujo; para la monitorización de procesos de biosorción de mezclas de metales de transición en raspo de uva, residual de la industria vinícola. Se emplearon diferentes lenguas electrónicas como método de detección y se lograron monitorizar satisfactoriamente diferentes mezclas, de dos, tres y cuatro componentes. Con la información adquirida, se obtuvieron los principales parámetros termodinámicos de los procesos estudiados, la capacidad de sorción (q0), la capacidad de sorción del volumen del lecho (N0) y el tiempo requerido para alcanzar el 50 % del sorbato (r). Estos fueron comparados con los modelos teóricos de Thomas, Yoon-Nelson y BDST, en todos los casos se obtuvo un buen ajuste. También se determinó el orden de selectividad del raspo de uva (biosorbente) hacia los diferentes metales estudiados y el mecanismo predominante y responsable de la biosorción fue el intercambio iónico.This thesis is focused on the development of advanced analytical tools based on potentiometric electronic tongues and artificial neural networks, for the determination of transition metal traces, particularly Cu(II), Cd(II), Pb(II) and Zn(II) in environmental samples. In the search for new recognition elements, two new bis-thiourea derivatives were synthesized and characterized, which were used as ionophores in lead selective electrodes. The electrodes obtained were fully characterized and yielded very good analytical parameters. The applicability of the two devices constructed was verified in the determination of lead in soil samples, the results obtained were compared successfully against a reference method (ICP-MS). Using these previously constructed electrodes in concert with additional electrodes exploiting commercially fabricated sensory elements, a sensor array was formed and thus used in various applications. The first of these applications was a potentiometric electronic tongue for the simultaneous determination of Cu2+, Cd2+, Pb2+ and Zn2+ at trace levels in soil samples. The model was constructed with the use of artificial neural networks and exhibited a very good fit and predictive ability. The proposed strategy was applied to the determination of these 4 analytes in soil samples. The results were also compared with a reference method (FAAS). In the second application, the electronic tongue was employed as end point detection method in titration system, to resolve ternary mixtures of transition metals. In order to reduce the analysis time, a complexometric fixed volume titration methodology was used. The multivariate information obtained was treated with artificial neural networks, and the Cu2+, Cd2+ and Pb2+ volumes were simultaneously determined in soil spiked samples, which represents a significant contribution to the state-of-the-art, as these applications are virtually impossible to achieve with conventional titration methodologies. Subsequent applications were focused on the development of an automated system based on electronic tongues and flow injection analysis, for the monitoring of biosorption processes of mixtures of transition metals in grape stalk, wine industry waste. Several electronic tongues were used as a detection method, and achieved the satisfactorily monitoring of different mixtures of two, three and four components. Using the obtained information, the main thermodynamic parameters of the studied processes were successfully determined; these were the sorption capacity (q0), the sorption capacity of the bed volume (N0) and the time required to reach 50% of the sorbate (r). These were then compared to theoretical models of Thomas, Yoon-Nelson and BDST in all cases a good fit was achieved. The mechanism responsible for biosorption, ion exchange, and the order of selectivity grape stalk (biosorbent) towards different metals studied was also determined

Potential use and performance studies of solar crop dryers in Mauritius

Part of African Energy Programme research report series no. 2Available from British Library Document Supply Centre- DSC:3490.17782(CSC-TP--238) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo