Heavy metal/toxins detection using electronic tongues

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOThe growing concern for sustainability and environmental preservation has increased the demand for reliable, fast response, and low-cost devices to monitor the existence of heavy metals and toxins in water resources. An electronic tongue (e-tongue) is a multisensory array mostly based on electroanalytical methods and multivariate statistical techniques to facilitate information visualization in a qualitative and/or quantitative way. E-tongues are promising analytical devices having simple operation, fast response, low cost, easy integration with other systems (microfluidic, optical, etc) to enable miniaturization and provide a high sensitivity for measurements in complex liquid media, providing an interesting alternative to address many of the existing environmental monitoring challenges, specifically relevant emerging pollutants such as heavy metals and toxins.73119FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOSem informaçã

Electrochemical stripping analysis

Electrochemical stripping analysis (ESA) is a trace electroanalytical technique for the determination of metal cations, inorganic ions, organic compounds and biomolecules. It is based on a pre-concentration step of the target analyte(s), or a compound of the target, on a suitable working electrode. This is followed by a stripping step of the accumulated analyte using an electroanalytical technique. Advantages of ESA include high sensitivity and low limits of detection, multi-analyte capability, low cost of instrumentation and consumables, low power requirements, potential for on-site analysis, speciation capability and scope for indirect biosensing. This Primer covers fundamental aspects of ESA and discusses methods of pre-concentration and stripping, instrumentation, types of working electrodes and sensors, guidelines for method optimization, typical applications, data interpretation and interferences, and method limitations and workarounds. Finally, the current trends and future prospects of ESA are highlighted

Recent advances in chemical sensors for soil analysis: a review

The continuously rising interest in chemical sensors' applications in environmental monitoring, for soil analysis in particular, is owed to the sufficient sensitivity and selectivity of these analytical devices, their low costs, their simple measurement setups, and the possibility to perform online and in-field analyses with them. In this review the recent advances in chemical sensors for soil analysis are summarized. The working principles of chemical sensors involved in soil analysis; their benefits and drawbacks; and select applications of both the single selective sensors and multisensor systems for assessments of main plant nutrition components, pollutants, and other important soil parameters (pH, moisture content, salinity, exhaled gases, etc.) of the past two decades with a focus on the last 5 years (from 2017 to 2021) are overviewed

Data analysis tools for safe drinking water production

Providing safe and high quality drinking water is essential for a high quality of life. However, the water resources in Europe are threatened by various sources of contamination. This has led to the development of concepts and technologies to create a basis for provision of safe and high quality drinking water, which had thus resulted in the formation of the Artificial Recharge Demonstration project (ARTDEMO). The overall aim of this thesis in relation to the ARTDEMO project was to develop a realtime automated water monitoring system, capable of using data from various complementary sources to determine the amounts of inorganic and organic pollutants. The application of multivariate calibration to differential pulse anodic stripping voltammograms and fluorescence spectra (emission and excitation-emission matrix) is presented. The quantitative determination of cadmium, lead and copper acquired on carbon-ink screen-printed electrodes, arsenic and mercury acquired on gold-ink screen-printed electrodes, in addition to the quantitative determination of anthracene, phenanthrene and naphthalene have been realised. The statistically inspired modification of partial least squares (SIMPLS) algorithm has been shown to be the better modelling tool, in terms of the root mean square error of prediction (RMSEP), in conjunction with application of data pre-treatment techniques involving rangescaling, filtering and weighting of variables. The % recoveries of cadmium, lead and copper in a certified reference material by graphite furnace atomic absorption spectrometry (GF-AAS) and multivariate calibration are in good agreement. The development of a prototype application on a personal digital assistant (PDA) device is described. At-line analysis at potential contamination sites in which an instant response is required is thus possible. This provides quantitative screening of target metal ions. The application imports the acquired voltammograms, standardises them against the laboratory-acquired voltammograms (using piecewise direct standardisation), and predicts the concentrations of the target metal ions using previously trained SIMPLS models. This work represents significant progress in the development of analytical techniques for water quality determination, in line with the ARTDEMO project's aim of maintaining a high quality of drinking water.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Voltammetric determination of metal ions beyond mercury electrodes. A review

For a long time mercury electrodes have been the main choice for the analysis of metal ions and some metalloids. However, in the last years, safety and environmental considerations have restricted their use and encouraged the search for alternative materials more environmentally friendly and with more possibilities for in-situ and flow analysis. This research has been reinforced by the popularisation of nanomaterials, biomolecules and screen-printed electrodes, as well as for the new advances in sensor miniaturization and integration of the electrodes in multi-sensor platforms and electronic tongues. The present review critically summarizes and discusses the progress made since 2010 in the development and application of new electrodes for the analysis of metals and metalloids

Real-Time Water Quality Monitoring with Chemical Sensors

Water quality is one of the most critical indicators of environmental pollution and it affects all of us. Water contamination can be accidental or intentional and the consequences are drastic unless the appropriate measures are adopted on the spot. This review provides a critical assessment of the applicability of various technologies for real-time water quality monitoring, focusing on those that have been reportedly tested in real-life scenarios. Specifically, the performance of sensors based on molecularly imprinted polymers is evaluated in detail, also giving insights into their principle of operation, stability in real on-site applications and mass production options. Such characteristics as sensing range and limit of detection are given for the most promising systems, that were verified outside of laboratory conditions. Then, novel trends of using microwave spectroscopy and chemical materials integration for achieving a higher sensitivity to and selectivity of pollutants in water are described

Biosensors for Environmental Monitoring

Real-time and reliable detection of molecular compounds and bacteria is essential in modern environmental monitoring. For rapid analyses, biosensing devices combining high selectivity of biomolecular recognition and sensitivity of modern signal-detection technologies offer a promising platform. Biosensors allow rapid on-site detection of pollutants and provide potential for better understanding of the environmental processes, including the fate and transport of contaminants.This book, including 12 chapters from 37 authors, introduces different biosensor-based technologies applied for environmental analyses

Zn(II) detection in biological samples with a smart sensory polymer

We have developed a new sensory material for the rapid and inexpensive determination of Zn(II), and we have carried out a proof of concept for the determination of Zn(II) in biological samples. The interaction with Zn(II) generates an OFF-ON fluorescence process on the material, which can be recorded both with a fluorimeter and with a smartphone by analyzing the RGB components of the taken photographs. This sensory material is prepared with 99.75% of commercially available monomers and contains 0.25% of a sensory monomer based on a quinoline structure. The sensory motifs are chemically anchored to the polymeric structure, and, accordingly, no migration of organic substances from the material occurs during the sensing process. Our method has been tested with freshly prepared Zn(II) aqueous solutions, but also with biological samples from exudates of chronic wounds. The proposed methodology provides limits of detection (LOD) of 13 and 27 ppb when employing a water-soluble polymer (WsP) and a hydrophilic polymeric film (HP), respectively, using emission spectroscopy. The measurements have been contrasted with ICP-MS as the reference method, obtaining reliable data. This study is the starting point toward a larger investigation with patients, which will address the challenge of establishing a direct relationship between the concentration of zinc(II), other cations and also of amino acids, with the protease activity and, finally, with the state/evolution of chronic wounds. In this context, the proposed sensory material and others we are now working with will act as a simple and cheap method for this purpose.FEDER (Fondo Europeo de Desarrollo Regional), and both the Spanish Ministerio de Economía, Industria y Competitividad (MAT2017-84501-R) and the Consejería de Educación—Junta de Castilla y León (BU061U16

Electrochemical Biosensor Arrays Utilising Bacteria and Aptamer Nano-bioreceptors for Toxic Chemicals Detection

This work was dedicated to development of novel biosensing technologies for detection of toxic chemicals, such as heavy metals, pesticides and petrochemicals, which possess a serious threat to humans and all living organisms in our planet nowadays. This was the main motivation for research in such important field. In the present work a novel approach in detection of heavy metal salts (HgCl2, PbCl2, ZnCl2 and CdCl2), pesticides (atrazine, simazine, DDVP), and petro-chemicals (hexane, octane, pentane, toluene, pyrene and ethanol) dissolved in water was proposed. It is based on a concept of inhibition sensor array utilising different whole bacteria cells. The main aim of this project is to develop novel, simple and cost-effective biosensing technologies for in-field detection of the above pollutants in water which effectively reduce the time and cost of analysis. Electrochemical detection appeared to be the most suitable for such task. In this project, three types of bacteria, e.g. Escherichia coli, Methylococcus capsulatus (Bath) or Methylosinus trichosporium (OB3b) and Shewanella oneidensis, were selected because of their different inhibition patterns. The concentration of live bacteria (which is an indicator of the presence of pollutants) was first characterised by the optical analytical methods of optical density OD600, fluorescence microscopy and flow cytometry. The main findings of this study were the facts that E. coli (K12 strain, gram-negative bacteria) are very sensitive to all above mentioned pollutants; methanotrophic bacteria (Mc. capsulatus Bath & Ms. trichosporium OB3b) appeared to be more resistant to petrochemicals; while S. oneidensis (MR-1 strain, gram negative bacteria) are more tolerant to heavy metals. A series of AC and DC electrochemical measurements were carried out on the same bacteria samples. As a first step, a correlation between optical and electrochemical characteristics of bacteria concentration in solution was established. The study of the effect of heavy metals, pesticides and petrochemicals on DC and electrical characteristics of bacteria in suspension revealed a similar inhibition pattern as was found in optical study. Then a similar study was carried out on samples of bacteria immobilized on the surface of screen-printed electrodes, which is more suitable for sensing applications. The results of DC (cyclic voltammograms) and AC (impedance spectroscopy) measurements were consistent with previous studies. A possibility of pattern recognition of pollutants by their inhibition effects on the selected bacteria was found. The classes of pollutants, e.g. heavy metals, pesticides, and petrochemicals, can be identified from pseudo-3D graphs of responses of the three sensing channels, e.g. electrodes with different immobilized bacteria. Much more accurate assessment of pollutants was achieved with Artificial Neural Network (ANN) software which was developed using MatLab. ANN programme was capable of both the identification of pollutants with 91% accuracy and rough estimation of their concentrations in five bands from 0.01 ng/ml to 1000 ng/ml (ppb). The developed bacteria sensor array could be suitable for simple, inexpensive, and quick preliminary in-field detection (screening) of water samples. The suspected highly contaminated samples could be easily identified and passed to specialized laboratories for further more detailed testing. In such way, the time and cost of analysis could be substantially reduced. In addition to the inhibition sensor array utilising non-specific bio-receptors such as bacteria, the electrochemical detection of heavy metal ions (Hg2+ and Pb2+) was attempted using novel highly specific aptamer bio-receptors labelled with redox groups. Such experiments were successful; the above metal ions in very low concentrations down to 1 pg/ml (or 1 ppt) were detected using both cyclic voltammograms and impedance spectroscopy. The affinity of the aptamers used was found to be very high and similar to that of antibodies. Additional advantages of aptamers were their high stability and simple recovery by thermo-cycling. Considering fast evolvement of aptamer research, their advantages and low cost, the development of aptasensor arrays for accurate detection of large number of pollutants is possible in near future

Desenvolupament de sensors i llengües electròniques voltamperomètriques per a la determinació d’ions metàl·lics en mostres d’interès ambientals

[cat] La problemàtica mediambiental associada a la contaminació per ions metàl·lics és mundialment coneguda. En les últimes dècades hi ha hagut un enduriment de la legislació associada a aquests contaminants que ha permès disminuir les seves emissions al medi ambient però, degut a la seva elevada persistència i al seu caràcter no biodegradable, les concentracions dels ions metàl·lics en mostres mediambientals són encara preocupants. Actualment, tot i que existeixen diverses tècniques analítiques per a la determinació d’ions metàl·lics, encara és necessari el desenvolupament de noves metodologies analítiques que permetin determinar-los on-site i a nivell traça. En aquest sentit, les tècniques voltamperomètriques de redissolució són una bona opció ja que són tècniques sensibles i reproduïbles que proporcionen anàlisis ràpides sense requerir instrumentació voluminosa o excessivament costosa. A més, el caràcter portàtil d’aquestes tècniques s’ha vist afavorit amb la introducció dels elèctrodes serigrafiats, que són dispositius compactes, miniaturitzats, versàtils i que es poden produir en massa. Un dels avantatges que proporcionen els elèctrodes serigrafiats és la possibilitat de modificar el seu elèctrode de treball per tal de millorar la seva sensibilitat i selectivitat o permetre treballar a diferents condicions experimentals. En aquest sentit, una primera part d’aquesta tesi doctoral s’ha centrat en el desenvolupament de nous elèctrodes serigrafiats voltamperomètrics per a la determinació d’ions metàl·lics a nivell traça en mostres mediambientals. Concretament, s’han estudiat diferents estratègies de modificació com la modificació química, la formació de pel·lícules metàl·liques i l’ús de diversos nanomaterials (nanopartícules metàl·liques, nanoal·lòtrops de carboni i silici porós). Per a cada estratègia s’han estudiat diferents aspectes del procés de modificació i s’ha avaluat l’aplicabilitat del sensor que proporciona millors resultats en mostres reals. Sovint però, en l’anàlisi de mostres reals trobem mescles complexes on els ions metàl·lics s’interfereixen entre si o donen lloc a pics solapats. En aquests casos l’ús d’un sol sensor no permet determinar correctament la concentració dels diferents ions i cal recórrer a altres estratègies d’anàlisi més sofisticades. Aquest és el cas de les llengües voltamperomètriques, on es combinen diversos sensors no específics amb un tractament de dades multivariant. Així, la segona part d’aquesta tesi doctoral s’ha centrat en el desenvolupament de llengües voltamperomètriques per a l’anàlisi de mostres complexes d’ions metàl·lics. Concretament s’han estudiat el sistema Tl(I) i In(III) i el sistema Cd(II), Pb(II), Tl(I) i Bi(III) en presència de Zn(II) i In(III), que es caracteritzen, respectivament, per la presència de dos metalls que donen lloc a senyals fortament solapats i per la presència d’un elevat nombre de metalls. Concretament, s’ha estudiat la selecció dels sensors que componen la llengua voltamperomètrica, la seva disposició i el disseny experimental. Un altre aspecte crucial en el desenvolupament de les llengües voltamperomètriques és el tractament de dades. Així, en la segona part d’aquesta tesi doctoral també s’ha fet èmfasi en aquest tema, on s’han estudiat diversos pretractaments i s’han construït diversos models quimiomètrics basats en la regressió per mínims quadrats parcials (PLS). A més, s’han estudiat també dos sistemes de calibratge multivariant, el calibratge multivariant extern i l’addició estàndard multivariant, per a la qual s’ha desenvolupat una nova estratègia basada en l’ús de PLS i la simulació del blanc de la mostra a partir de l’omissió de l’etapa de preconcentració de la mesura voltamperomètrica. Aquest segon mètode de calibratge proporciona prediccions més acurades per a mostres amb un fort efecte matriu. Els resultats obtinguts a partir dels estudis realitzats al llarg d’aquesta tesi doctoral han donat lloc a 12 articles, 9 d’ells referents a la part de desenvolupament de sensors voltamperomètrics i 3 referents al desenvolupament de llengües voltamperomètriques.[eng] On-site monitoring of metal ions at trace levels is crucial for safety and environmental reasons. In this sense, stripping voltammetry is a good option due to its high sensitivity and reproducibility and the fact that it provides fast analysis with relatively low cost and portable equipment. These last features are further enhanced by the coupling of stripping voltammetry with screen-printed electrodes, which are compact, miniaturized and versatile devices that can be mass-produced in a reproducible manner. A first part of this PhD thesis has focused on the development of new screen-printed voltammetric sensors for the determination of metal ions at trace levels in environmental samples. Particularly, several modification strategies (chemical modification, metal films and nanomaterials) have been studied. For each strategy, some aspects of the modification process were evaluated and their applicability to real samples was tested for the sensor that provided better results. Frequently though, the analysis of real samples involves complex mixtures where metal ions interact with each other or give rise to highly overlapped peaks. In these scenarios, it is necessary to resort to more sophisticated analytical strategies like voltammetric electronic tongues. Thus, the second part of this PhD thesis has focused on the development of voltammetric tongues for the analysis of complex mixtures of metal ions. In particular, two systems have been studied: Tl(I) and In(III), two metals that give rise to highly overlapped peaks, and Cd(II), Pb(II), Tl(I) and Bi(III) in the presence of Zn(II) and In(III). In both cases, several studies involving the selection of sensors, their arrangement and the experimental design were performed. The second part of this PhD thesis has also focused on data treatment, a key aspect in the development of voltammetric tongues. Two multivariate calibration systems were studied, multivariate external calibration and multivariate standard addition, for which a new strategy based on PLS and the simulation of a blank signal by skipping the deposition step of stripping voltammetry was developed. The results achieved throughout this PhD thesis have resulted in 12 articles, 9 related to the development of voltammetric sensors and 3 related to the development of voltammetric electronic tongues