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The negative impacts of microplastics on the environment and human health cannot be unnoticed. Several classes of emerging pollutants with endocrine-disrupting properties such as bisphenol A and its analogs, phthalates, among others, have been reported to migrate out of plastics entering the aquatic environment. Thus, this review aims to draw attention to the significant potential of the boron-doped diamond electrode to contribute to the implementation of mitigation actions for microplastic pollutants. The latest studies in the two main fields of the use of the boron-doped diamond electrode, that is, treatment of wastewater by electrochemical oxidation and a as sensor for pollutants monitoring, are herein reviewed and their main findings highlighted., T.M.B.F. Oliveira and F.W.P. Ribeiro thank FUNCAP (Proc. BP4-0172-00111.01.00/20 and BP4-0172-00150.01.00/20), CNPq (Proc. 308108/2020-5, 420261/2018-4, and 406135/2018-5), and UFCA for their financial support. S. Morais acknowledges UIDB/50006/2020 and UIDP/50006/2020 fundings and PTDC/ASP-PES/29547/2017 (POCI-01-0145-FEDER-029547) funded by FEDER funds through the POCI and by National Funds through FCT. P. de Lima-Neto and A.N. Correia gratefully thank CNPq (proc. 408626/2018-6, 304152/2018-8, 305136/2018-6, and 405596/2018-9) and FCT/Funcap (proc. FCT-00141-00011.01.00/18).

Pharmaceuticals, as a contaminant of emergent concern, are being released uncontrollably into the environment potentially causing hazardous effects to aquatic ecosystems and consequently to human health. In the absence of well-established monitoring programs, one can only imagine the full extent of this problem and so there is an urgent need for the development of extremely sensitive, portable, and low-cost devices to perform analysis. Carbon-based nanomaterials are the most used nanostructures in (bio)sensors construction attributed to their facile and well-characterized production methods, commercial availability, reduced cost, high chemical stability, and low toxicity. However, most importantly, their relatively good conductivity enabling appropriate electron transfer rates—as well as their high surface area yielding attachment and extraordinary loading capacity for biomolecules—have been relevant and desirable features, justifying the key role that they have been playing, and will continue to play, in electrochemical (bio)sensor development. The present review outlines the contribution of carbon nanomaterials (carbon nanotubes, graphene, fullerene, carbon nanofibers, carbon black, carbon nanopowder, biochar nanoparticles, and graphite oxide), used alone or combined with other (nano)materials, to the field of environmental (bio)sensing, and more specifically, to pharmaceutical pollutants analysis in waters and aquatic species. The main trends of this field of research are also addressed., This work was financially supported by: projects UID/QUI/50006/2019 and PTDC/ASP-PES/29547/2017 (POCI-01-0145-FEDER-029547) funded by FEDER funds through the POCI and by National Funds through FCT - Foundation for Science and Technology. This proposal was also subsidized by the Brazilian agencies CNPq (Proc. 420261/2018-4) and CAPES (Proc. 88881.140821/2017-01; Finance code 001). F.W.P. Ribeiro acknowledges funding provided by FUNCAP-BPI (Proc. BP3-0139-00301.01.00/18). Acknowledgments T.M.B.F. Oliveira thanks the UFCA’s Pro-Rectory of Research and Innovation for initiating his investigations. F.W.P. Ribeiro thanks the CNPq (proc. 406135/2018-5) and all support provided by the UFCA‘s Pro-Rectory of Research and Innovation. A.N. Correia thanks the CNPq (proc. 305136/2018-6).

Carbohydrates and glycoconjugates are involved in numerous natural and pathological metabolic processes, and the precise elucidation of their biochemical functions has been supported by smart technologies assembled with lectins, i.e., ubiquitous proteins of nonimmune origin with carbohydrate-specific domains. When lectins are anchored on suitable electrochemical transducers, sensitive and innovative bioanalytical tools (lectin-based biosensors) are produced, with the ability to screen target sugars at molecular levels. In addition to the remarkable electroanalytical sensitivity, these devices associate specificity, precision, stability, besides the possibility of miniaturization and portability, which are special features required for real-time and point-of-care measurements. The mentioned attributes can be improved by combining lectins with biocompatible 0-3D semiconductors derived from carbon, metal nanoparticles, polymers and their nanocomposites, or employing labeled biomolecules. This systematic review aims to substantiate and update information on the progress made with lectin-based biosensors designed for electroanalysis of clinically relevant carbohydrates and glycoconjugates (glycoproteins, pathogens and cancer biomarkers), highlighting their main detection principles and performance in highly complex biological milieus. Moreover, particular emphasis is given to the main advantages and limitations of the reported devices, as well as the new trends for the current demands. We believe that this review will support and encourage more cutting-edge research involving lectin-based electrochemical biosensors.

The electrochemical degradation of long-chain phenols present in toxic residues from the cashew-nut processing industry was systematically investigated for the first time, using a flow electrochemical reactor assembled with a Ti/TiO2-RuO2-IrO2 DSA anode. After optimizing the current density (40 mA cm−2) and chloride concentration (0.028 mol L−1) in 0.5 mol L−1 Na2SO4 supporting electrolyte, it was achieved expressive total organic carbon (TOC) removal percentage for (un)saturated cardanol and cardol, either alone (85–92%) or in association/real industrial CNSL sample (82%), over 4 h of electrolysis. Evidently, the removal rate for the mixture changes (56–88% TOC removal) according to its starting concentration (0.005–0.100% residue), showing that the system performance can improve by increasing treatment time. Chromatography coupled to mass spectrometry (GC–MS) analysis showed that the first stage of the electrooxidation process was driven towards the formation of phenoxyl radicals, followed by the formation of polymeric dimers. These intermediates were continuously oxidized by different free and chemisorbed reactive species until obtaining short-chain organic acids, CO2 and H2O. The proposed system proved to be efficient, eco-friendly, and viable to treat industrial waste containing refractory phenolic compounds.

An electroanalytical method for determining dienestrol (DNL) in bovine urine samples is described. A glassy carbon electrode (GCE) modified with silver nanoparticles and functionalized multi-walled carbon nanotubes was used as working sensor. The modified GCE displays substantial analytical improvements including an amplified signal, fast electron transfer kinetics, and resistance to fouling. The irreversible oxidation signal of DNL is pH-dependent. Best reactivity is found at pH 3.0, where a typical anodic peak is recorded at 0.8 V (vs. Ag/AgCl). Square-wave voltammetry revealed a 8.4 nM detection limit (1.9 μg L−1), good repeatability and reproducibility (RSDs

Boron‐doped diamond (BDD) electrodes possess outstanding physical, chemical, and electronic properties and have been successfully, yet in a limited way, explored in the electroanalysis of substances with therapeutic action (analgesics, antipyretics, antibiotics, anti‐inflammatories, antihypertensives, antidepressants, vitamins, and others) in diverse milieus (pharmaceutical formulations, urine, serum, whole blood, surface waters, seawaters, groundwater, wastewaters, etc.). Therefore, in this Review, a broad overview of the available scientific information on recent progress and achievements of the application of bare or modified BDD electrodes to the bioanalytical and environmental detection of pharmaceutical compounds is presented. The main parameters, for example boron concentration, applied operational conditions during pretreatment, chemical and physical structure, and other influential factors on the electroanalytical BDD electrodes performance, are discussed., Funding Information: CNPq-INCT. Grant Numbers: 573925/2008-9, 573548/2008-0 CAPES/Funcap. Grant Numbers: 2133/2012/proc. 23038.007973/2012-90, PNE-0112-00048.01.00/16 CNPq. Grant Numbers: 400223/2014-7, 303596/2014-7, 302801/2014-6, 408790/2016-4 PRONEX/Funcap. Grant Number: PR2-0101-00030.01.00/15 FCT/Funcap. Grant Number: FCT-00141-00011.01.00/18 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -Brasil (CAPES). Grant Number: 001 CAPES-PNPD FUNCAP-BPI. Grant Number: BP3-0139-00301.01.00/18 CNPq CAPES FUNCAP UFCA's Pro-Rectory CNPq. Grant Number: 304419/2015-0 European Union (FEDER funds through COMPETE) National Funds (Fundação para a Ciência e Tecnologia-FCT). Grant Numbers: UID/QUI/50006/2013, PTDC/ASP-PES/29547/2017 FCT/MEC Norte Portugal Regional Operational Programme (NORTE 2020). Grant Numbers: Norte-01-0145-FEDER-000011, Norte-01-0145-FEDER-000024

Aware of the irreparable damage that synthetic estrogens can trigger in the environment, the search for analytical methods capable of mapping the sources, levels and fate of these micropollutants is a subject that demands enormous scientific effort. The present work follows this trend, reporting a silver nanoparticles/single-walled carbon nanotubes-based composite electrode (AgNP/SWCNT-CPE) that has multiple functionalities for dienestrol (DNL) electroanalysis. Theoretical and experimental data indicate that DNL reactivity on AgNP/SWCNT-CPE is more critical under acidic conditions, favoring its irreversible oxidation to quinone derivatives. The reaction kinetics is limited by interfacial adsorption events, whose intensity of the molecule-surface interaction depends on variables such as Gibbs free energy, ionization potential, HOMO-LUMO gap, and dipole moment. Since the silver‑carbon heterojunction has low overpotential towards the oxygen evolution reaction, it is speculated that AgNP/SWCNT-CPE is more resistant to surface fouling due to the formation of chemisorbed radicals on its electroactive area. Based on the detection limit (43.7 nmol L−1 DNL), the analytical performance of the proposed method is equivalent to those attained by chemiluminescence, electrophoresis, chromatography and electrochemistry. Given the sensitivity obtained, AgNP/SWCNT-CPE was successfully used to quantify DNL in river waters containing different levels of organic matter, without compromising the accuracy, stability and robustness of the amperometric measurements, reiterating the reliability and feasibility of this proposal.

The yeast Saccharomyces cerevisiae, a microorganism with cell walls resistant to many types of treatments, was chosen as a model to study electrochemical disinfection process using dimensionally stable anodes (DSA). DSA electrodes with nominal composition of Ti/RuO2TiO2 and Ti/RuO2TiO2IrO2 were evaluated in 0.05 mol L−1 Na2SO4 containing yeast. The results showed inactivation about of 100 % of the microorganisms at Ti/RuO2TiO2 by applying 20 and 60 mA cm−2 after 120 min of electrolysis, while a complete inactivation at Ti/RuO2IrO2TiO2 electrode was achieved after 180 min at 60 mA cm−2. When chloride ions were added in the electrolyte solution, 100 % of the yeast was inactivated at 20 mA cm−2 after 120 min of electrolysis, independent of the anode used. In the absence of chloride, the energy consumption (EC) was of 34.80 kWh m−3, at 20 mA cm−2 by using Ti/RuO2TiO2 anode. Meanwhile, in the presence of chloride, EC was reduced, requiring 30.24 and 30.99 kWh m−3 at 20 mA cm−2, for Ti/RuO2TiO2 and Ti/RuO2IrO2TiO2 electrodes, respectively, The best performance for cell lysis was obtained in the presence of chloride with EC of 88.80 kWh m−3 (Ti/RuO2TiO2) and 91.85 kWh m−3 (Ti/RuO2IrO2TiO2) to remove, respectively, 92 and 95 % of density yeast. The results clearly showed that yeast, as a model adopted, was efficiently inactivated and lysed by electrolysis disinfection using DSA-type electrodes.

Food quality control has been a pressing issue in recent years and demands the development of efficient and versatile analytical methods. This paper describes a promising voltammetric assay to monitor the synthetic estrogen E,E-dienestrol (E,E-DNL) in fish tissue, using a cathodically pretreated boron-doped diamond (Cpt-BDD) electrode in combination with QuEChERS extraction method. The electrochemical reactivity of E,E-DNL on Cpt-BDD electrode is strongly pH-dependent, so that a well-defined anodic peak (≈ 0.97 V vs. Ag/AgCl) was recorded in Britton-Robinson buffer (pH = 2.0) due to oxidation of estrogen to quinone. This behavior became much more evident after cathodic pretreatment of the working electrode, since the hydrogen-terminations produced on the active surface improve the charge-transfer process, signal-to-background ratio and fouling resistance. When estrogen oxidation current was observed by square-wave voltammetry under optimum conditions, it was found a linear relationship from 2.30 × 10–7 to 9.69 × 10–6 mol L–1 E,E-DNL, with high data correlation (R2 = 0.9987), sensitivity (detection limit of 5.43 × 10–8 mol L–1) and precision (RSD

Carbamate pesticides (CBMs) are esters and thioesters derived from carbamic acid, which are widely used to increase agricultural productivity and to protect human and animal health from insect-vector-mediated diseases. However, they can be highly toxic when not appropriately applied. Electrochemical carbon-based sensors and biosensors gather a plethora of advantages for reliable, low cost, rapid and even in loco quality control and surveillance of CBMs levels in all systems related to environmental and human health. Thus, this review presents a broad overview of the state-of-art of design and applications of these (bio)sensors for CBMs electroanalysis in environmental, food and biological matrices with emphasis in the role of the carbon (nano)materials. The latest advances and trends but also the main (bio)sensors limitations and research gaps are highlighted. Highly selective, robust and novel carbon-based (bio)sensors with multiplexing CBMs capability are envisaged to emerge shortly for in-field applicability.

Glossoscolex paulistus hemoglobin structure is composed of 144 globin chains and 36 polypeptide chains lacking the heme group, with a total molecular mass of 3600 kDa. The current study focuses on the oxy-HbGp oligomeric stability, as a function of the storage time, at pH 7.0, using dynamic light scattering, analytical ultracentrifugation (AUC), optical absorption and size exclusion chromatography (SEC). HbGp stored in Tris-HCl buffer, pH 7.0, at 4 °C, for two years remains in the native form, while 4–6 years HbGp stocks present typical hemichrome species absorption spectra. AUC and SEC analyses show that the contribution of HbGp-subunits, such as, dodecamer (abcd)3, tetramer abcd, trimer abc and monomer d, increases with the protein aging due to the lower stability of the HbGp with the time. The dissociation and the oxidation of the iron noted for the older protein solutions indicate that HbGp storage for periods of time longer than two years changes its ability to carry oxygen. Despite the reduction of HbGp stability and oxygen carrying capacity with aging, the protein stability is still larger as compared to mammalian hemoglobins. Thus, the extracellular hemoglobins are quite stable and resistant to the auto-oxidation process, making them of interest for biotechnological applications.

Environmental heavy-metals contamination is a worldwide concern and the treatment of their sources constitutes a sustainable and efficient alternative. This work investigated the performance of Malpighia emarginata D.C. seed fibers microparticles (Me-SFMp) as biosorption platform for heavy metal ions. Integrated physicochemical analyses (FAAS, FTIR, SEM/EDS and XRF) showed that such ability was associated with the high microstructural porosity, wide surface area and diversity of functional groups on Me-SFMp structures, which favored the high and fast uptake of the target-substances (Cd, Zn, Cr, Pb, Cu and Ni ions). In terms of reactional kinetics, the pseudo-second order model showed better data correlation (R2 from 0.9992 to 0.9998) and suggested the chemisorption as limiting step of the reaction mechanisms. From the Langmuir isotherms (R2 from 0.9993 to 0.9998), it was observed that these phenomena occurred non-linearly on a homogeneous biosorbent monolayer. Me-SFMp can also be reused after desorption processes conducted in acid medium and, under ideal conditions (0.8 g biosorbent dosage; 100 mL of 1.00 mg L–1 multi-metal solution adjusted to pH = 8.0; 300 rpm stirring speed; and 60 min contact time), the following maximum removal percentages order was observed for the first cycle: Cd (100%) = Zn (100%) > Cr (95.1%) > Pb (86.8%) > Cu (84.2%) > Ni (81.0%). The procedure was successfully applied to remove the studied heavy metal ions from raw landfill leachate, even in the presence of several (in)organic interferers, reinforcing the strong biosorbent-adsorbate interaction and the viability of this proposal.

In this work, a functionalized multi-walled carbon nanotubes modified glassy carbon electrode (GCE/MWCNT-f) was optimized for the direct determination of imidacloprid (IMC) insecticide in river water. The functionalized material was characterized by infrared spectroscopy with Fourier transform (FTIR) and the modified electrode by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Results revealed that the GCE/MWCNT-f effectively increased the response toward IMC reduction by enhancing the reduction peak current and decreasing the peak potential in comparison with the bare electrode. After optimizing the electroanalytical conditions, the GCE/MWCNT-f showed a linear voltammetric response at concentration ranging from 2.40 × 10−7 to 3.50 × 10−6 mol L−1, with detection and quantification limits of 4.15 × 10−7 mol L−1 and 1.38 × 10−6 mol L−1, respectively. The recovery rate of IMC in spiked river water samples varied from 90–95%. Thus, this sensor can be a promising tool for the analysis and monitoring of IMC in complex environmental matrices.

Herein, a highly sensitive and selective simultaneous electrochemical method to monitor the emerging organic contaminants tartrazine (TRT), dexamethasone (DMZ) and diclofenac (DCL) in sewage treatment plants was developed. The sensing was based on electroreduction of TRT (−0.22 V), DMZ (−0.93 V) and DCL (−1.12 V) on hanging mercury drop electrode (HMDE), using citrate buffer pH 2.5 as electrolyte. The fast electrodic kinetics of these chemicals provided improvements on selectivity at high scan rates. The unique electrochemical properties of HMDE were associated to analytical performance of the square-wave voltammetry to quantify trace concentrations of TRT, DMZ and DCL, with detection limits ranging from 2.78 × 10 −8 to 1.48 × 10 −7 mol L −1 . After wastewater treatment by using solid-phase extraction, the proposed procedure was successfully applied for the direct quantification of the studied compounds with high precision, accuracy and stability of the measurements, even in the presence of other electroactive contaminants.

This study investigated the anodic oxidation of phenolic wastewater generated by cashew-nut processing industry (CNPI) using active (Ti/RuO2-TiO2) and inactive (boron doped diamond, BDD) anodes. During electrochemical treatment, various operating parameters were investigated, such as current density, chemical oxygen demand (COD), total phenols, O2 production, temperature, pH, as well as current efficiency and energy consumption. After electrolysis under optimized working conditions, samples were evaluated by chromatography and toxicological tests against L. sativa. When both electrode materials were compared under the same operating conditions, higher COD removal efficiency was achieved for BDD anode; achieving lower energy requirements when compared with the values estimated for Ti/RuO2-TiO2. The presence of Cl− in the wastewater promoted the electrogeneration of strong oxidant species as chlorine, hypochlorite and mainly hypochlorous acid, increasing the efficiency of degradation process. Regarding the temperature effect, BDD showed slower performances than those achieved for Ti/RuO2-TiO2. Chromatographic and phytotoxicity studies indicated formation of some by-products after electrolytic process, regardless of the anode evaluated, and phytotoxic action of the effluent. Results encourage the applicability of the electrochemical method as wastewater treatment process for the CNPI, reducing depuration time.

This paper describes the electroanalytical study of the organochlorine pesticide endosulfan (EDS) using square-wave voltammetry. The electrochemical behaviour showed a quasi-reversible process on a hanging mercury drop electrode (HMDE) in acid medium attributed to reduction of the carbon–chlorine bond. The constant of change transfer obtained for this process was 354 s − 1 . The redox mechanism was confirmed by quantum-chemical (Density Functional Theory, DFT) studies. The optimised experimental and voltammetric parameters were 0.04 mol L − 1 Britton–Robinson buffer (pH 4.0), the pulse potential frequency of 200 s − 1 , the amplitude of the pulse of 20 mV, and the height of the potential step of 4 mV. Analytical parameters such as linearity range, equation of the analytical curves, correlation coefficients, detection and quantification limits, recovery values, precision, and accuracy were obtained. The procedure was applied to the analysis of pesticide in complex samples: sugar cane, tomato, and raw natural waters. The recovery values demonstrated that the proposed methodology is suitable for determining EDS in such samples. The results indicated that the proposed procedure is stable and sensitive, with good reproducibility, and no complex procedure was necessary for sample preparation. The development of this electroanalytical procedure is therefore appropriate, as it provides adequate sensitivity and reliable methodology.

This paper describes the development and electrochemical behaviour of a quick, easy, cheap and eco-friendly electroanalytical procedure for the direct analysis of dimethomorph fungicide (DIM) in natural water samples using a carbon-fibre microelectrode (CFM) coupled with square-wave voltammetry (SWV). The optimized experimental and voltammetric parameters employed were a 0.04 mol L− 1 Britton–Robinson buffer (pH 3.0), a pulse potential frequency of 70 s− 1, a pulse amplitude of 30 mV and a scan increment of 2 mV. It was possible to observe a well-shaped oxidation peak at + 1.25 V (vs. Ag/AgCl/saturated Cl–), which was related to a two-electron transfer in the quasi-reversible redox process affected by a strong adsorption of reactants and products on the electrode surface. Analytical parameters such as linearity range, correlation coefficients, detection and quantification limits were evaluated and compared to similar results obtained using gas chromatography coupled with mass spectrometry. However, by using SWV, no clean-up, extraction or pre-concentration procedures were necessary, making the electroanalytical procedure more feasible for analytical routine analysis.

This study presents the preparation of a nanostructured films with an amphiphilic meso-porphyrin whose side chains are derived from cardanol, a byproduct of the cashew industry. The Langmuir films were prepared on acidified water to reducing the self-aggregation of the complex and the mean molecular area for the meso-porphyrin measured by surface pressure isotherms was 177 A2 and confirmed by compressibility modulus. The 700 nm band observed in the Langmuir films supports the coexistence of monomers and dimers similar to the spectra of the solution (CHCl3/CH3COOH). The formation of bright block domains with different sizes and shapes for the monolayer disappears after surface pressure starts to increase (π ≥ 2 mN m−1), as observed by Brewster angle microscopy measurements. Results of UV–vis spectra of the Langmuir films and FTIR reflection of the Langmuir–Blodgett (LB) films of meso-porphyrin indicated that the molecules exhibit preferential orientation with the planes perpendicular to the water (Langmuir) and parallel to the substrate (LB) surface. The LB films were tested as a promethazine sensor, which detected a concentration of 2 μM, a value greater than those obtained by other nanostructured systems.

This study focused on the development of a sensitive enzymatic biosensor for the determination of pirimicarb pesticide based on the immobilization of laccase on composite carbon paste electrodes. Multi-walled carbon nanotubes (MWCNTs) paste electrode modified by dispersion of laccase (3%, w/w) within the optimum composite matrix (60:40%, w/w, MWCNTs and paraffin binder) showed the best performance, with excellent electron transfer kinetic and catalytic effects related to the redox process of the substrate 4-aminophenol. No metal or anti-interference membrane was added. Based on the inhibition of laccase activity, pirimicarb can be determined in the range 9.90 × 10(-7) to 1.15 × 10(-5) mol L(-1) using 4-aminophenol as substrate at the optimum pH of 5.0, with acceptable repeatability and reproducibility (relative standard deviations lower than 5%). The limit of detection obtained was 1.8 × 10(-7) mol L(-1) (0.04 mg kg(-1) on a fresh weight vegetable basis). The high activity and catalytic properties of the laccase-based biosensor are retained during ca. one month. The optimized electroanalytical protocol coupled to the QuEChERS methodology were applied to tomato and lettuce samples spiked at three levels; recoveries ranging from 91.0 ± 0.1% to 101.0 ± 0.3% were attained. No significant effects in the pirimicarb electroanalysis were observed by the presence of pro-vitamin A, vitamins B1 and C, and glucose in the vegetable extracts. The proposed biosensor-based pesticide residue methodology fulfills all requisites to be used in implementation of food safety programs.

This work studied the antioxidant action of technical CNSL constituents, cardol (CD) and cardanol (CDN), and its synthetic derivative terc-butylated cardanol (terc-CDN) by electrochemical and computational methods. The electrochemical analyses were performed by square wave voltammetry and cyclic voltammetry in different pHs. The results showed that all compounds presented lower oxidation potentials when compared to the commercial product BHT (Epa = 0.989 V). Cardol presented the best values (Epa = 0.665 V), followed by terc-CDN (Epa = 0.682 V) and CDN (Epa = 0.989 V). The energy of the HOMO and LUMO orbitals, the Milliken charge and the analysis of molecular convergence obtained by computational methods confirmed the results obtained in electrochemical analysis proving that both techniques can be efficiently applied to this type of study.

This paper describes an electroanalytical methodology using square-wave adsorptive voltammetry, which has been successfully applied for the direct determination of dexamethasone residues in raw natural waters used for the public supply of the Ceará State, Brazil. The obtained detection limits ranged from 7.47 × 10-9 to 1.80 × 10-8 mol L-1 for the three matrices of raw natural waters evaluated. High percentages of average recovery (98.86% ± 0.72), repeatability (0.32% ± 0.05) and reproducibility (0.91% ± 0.20) were obtained in these samples, reaffirming the sensitivity of the procedure. Energy of the LUMO orbitals and Mülliken’s atomic charges were calculated using the functional BLYP/DNP. The theoretical results allied to the diagnostic criteria of the square-wave voltammetry indicate that the dexamethasone redox mechanism is associated to the quasi-reversible and irreversible reduction process of the ketone groups located at C-20 and C-3, respectively. Este trabalho descreve uma metodologia eletroanalítica, utilizando voltametria adsortiva de onda quadrada, que foi aplicada com êxito na determinação direta de resíduos de dexametasona em águas naturais brutas utilizadas no abastecimento público do Estado do Ceará, Brasil. Os limites de detecção obtidos variaram entre 7,47 × 10-9 e 1,80 × 10-8 mol L-1 para as três matrizes de águas naturais brutas avaliadas. Os valores percentuais médios de recuperação (98,86% ± 0,72), repetibilidade (0,32% ± 0,05) e reprodutibilidade (0,91% ± 0,20) foram significativos, reafirmando a sensibilidade do procedimento. A energia dos orbitais LUMO e as cargas atômicas de Mülliken foram calculadas usando o funcional BLYP/DNP. Os resultados teóricos, aliados aos critérios de diagnóstico da voltametria de onda quadrada, indicam que o mecanismo redox da dexametasona está associado a processos de redução quase-reversível e irreversível dos grupos cetona localizados em C-20 e C-3, respectivamente.

Multi-walled carbon nanotubes (MWCNT) have provided unprecedented advances in the design of electrochemical sensors. They are composed by sp2 carbon units oriented as multiple concentric tubes of rolled-up graphene, and present remarkable active surface area, chemical inertness, high strength, and low charge-transfer resistance in both aqueous and non-aqueous solutions. MWCNT are very versatile and have been boosting the development of a new generation of electrochemical sensors with application in medicine, pharmacology, food industry, forensic chemistry, and environmental fields. This work highlights the most important synthesis methods and relevant electrochemical properties of MWCNT for the construction of electrochemical sensors, and the numerous configurations and successful applications of these devices. Thousands of studies have been attesting to the exceptional electroanalytical performance of these devices, but there are still questions in MWCNT electrochemistry that deserve more investigation, aiming to provide new outlooks and advances in this field. Additionally, MWCNT-based sensors should be further explored for real industrial applications including for on-line quality control., Simone Morais is grateful for financial support from the European Union (FEDER funds through COMPETE) and National Funds (Fundação para a Ciência e Tecnologia-FCT) through projects UID/QUI/50006/2013 and AAC No. 02/SAICT/2017—project No. 029547 “CECs(Bio)Sensing—(Bio)sensors for assessment of contaminants of emerging concern in fishery commodities”, by FCT/MEC with national funds and co-funded by FEDER. She also thanks financial support by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF): projects Norte-01-0145-FEDER-000011 and Norte-01-0145-FEDER-000024. Acknowledgments: T.M.B.F. Oliveira thanks the Brazilian agencies CNPq, CAPES and FUNCAP for all scientific support to his projects with nanostructured materials.

A bacia hidrográfica Apodi/Mossoró é um dos mais importantes recursos hídricos do Rio Grande do Norte. Estudos recentes mostraram que os compostos nitrogenados destacam-se entre os principais contaminantes deste corpo aquático, mostrando a necessidade de relacioná-los com outras propriedades físico-químicas que influenciam na dinâmica das suas formas. Deste modo, este trabalho tem por objetivo correlacionar as concentrações de NO3-, NO2- e NH3 com os valores de pH, T, Eh e OD nas águas desta bacia. Os resultados indicam o predomínio de um meio fortemente oxidante, destacando o NO3- como a principal forma de nitrogênio presente, mesmo nos locais onde foram observadas reduções significativas de Eh e OD. Este trabalho busca contribuir para o desenvolvimento de medidas de controle e manejo das fontes poluidoras e o melhor gerenciamento deste recurso hídrico.

A bi-enzymatic biosensor (LACC–TYR–AuNPs–CS/GPE) for carbamates was prepared in a single step by electrodeposition of a hybrid film onto a graphene doped carbon paste electrode (GPE). Graphene and the gold nanoparticles (AuNPs) were morphologically characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, dynamic light scattering and laser Doppler velocimetry. The electrodeposited hybrid film was composed of laccase (LACC), tyrosinase (TYR) and AuNPs entrapped in a chitosan (CS) polymeric matrix. Experimental parameters, namely graphene redox state, AuNPs:CS ratio, enzymes concentration, pH and inhibition time were evaluated. LACC–TYR–AuNPs–CS/GPE exhibited an improved Michaelis–Menten kinetic constant (26.9 ± 0.5 M) when compared with LACC–AuNPs–CS/GPE (37.8 ± 0.2 M) and TYR–AuNPs–CS/GPE (52.3 ± 0.4 M). Using 4-aminophenol as substrate at pH 5.5, the device presented wide linear ranges, low detection limits (1.68 × 10 − 9 ± 1.18 × 10 − 10 –2.15 × 10 − 7 ± 3.41 × 10 − 9 M), high accuracy, sensitivity (1.13 × 10 6 ± 8.11 × 10 4 –2.19 × 10 8 ± 2.51 × 10 7 %inhibition M − 1 ), repeatability (1.2–5.8% RSD), reproducibility (3.2–6.5% RSD) and stability (ca. twenty days) to determine carbaryl, formetanate hydrochloride, propoxur and ziram in citrus fruits based on their inhibitory capacity on the polyphenoloxidases activity. Recoveries at two fortified levels ranged from 93.8 ± 0.3% (lemon) to 97.8 ± 0.3% (orange). Glucose, citric acid and ascorbic acid do not interfere significantly in the electroanalysis. The proposed electroanalytical procedure can be a promising tool for food safety control.

A novel enzymatic biosensor for carbamate pesticides detection was developed through the direct immobilization of Trametes versicolor laccase on graphene doped carbon paste electrode functionalized with Prussian blue films (LACC/PB/GPE). Graphene was prepared by graphite sonication-assisted exfoliation and characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The Prussian blue film electrodeposited onto graphene doped carbon paste electrode allowed considerable reduction of the charge transfer resistance and of the capacitance of the device. The combined effects of pH, enzyme concentration and incubation time on biosensor response were optimized using a 23 full-factorial statistical design and response surface methodology. Based on the inhibition of laccase activity and using 4-aminophenol as redox mediator at pH 5.0, LACC/PB/GPE exhibited suitable characteristics in terms of sensitivity, intra- and inter-day repeatability (1.8–3.8% RSD), reproducibility (4.1 and 6.3% RSD), selectivity (13.2% bias at the higher interference:substrate ratios tested), accuracy and stability (ca. twenty days) for quantification of five carbamates widely applied on tomato and potato crops. The attained detection limits ranged between 5.2×10−9 mol L−1 (0.002 mg kg−1 w/w for ziram) and 1.0×10−7 mol L−1 (0.022 mg kg−1 w/w for carbofuran). Recovery values for the two tested spiking levels ranged from 90.2±0.1 (carbofuran) to 101.1±0.3% (ziram) for tomato and from 91.0±0.1% (formetanate) to 100.8±0.1% (ziram) for potato samples. The proposed methodology is appropriate to enable testing pesticide levels in food samples to fit with regulations and food inspections.

The electrochemical reduction behavior of dexamethasone at a hanging mercury drop electrode was investigated by cyclic and square-wave adsorptive voltammetries in a Britton–Robinson buffer at pH 2.0. The optimized experimental conditions consisted of a pulse potential frequency of 100 s −1 , a pulse amplitude of 15 mV, and a potential step height of 2 mV, with E acc = −0.60 V and t acc = 15 s. From these parameters, it was also possible to develop a detailed study about the kinetic and mechanistic events involved in the reduction process. Two well-defined peaks were observed in the cathodic scan, and peak 2 was used to obtain analytical curves. A linear range between 4.98 × 10 −8 and 6.10 × 10 −7 mol L −1 , with a detection limit of 2.54 × 10 −9 mol L −1 and a quantification limit of 8.47 × 10 −9 mol L −1 , was observed. Moreover, it was possible to achieve a simple, selective, and versatile methodology adaptable to the quantification of dexamethasone because common excipients used in multicomponent commercial formulations caused no interference. The satisfactory recoveries and the low relative standard deviation data reflected the high accuracy and precision of the proposed method for the determination of dexamethasone in injectable eye drops and elixir samples.