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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).

Monte Carlo simulations were performed to evaluate the interaction between acetaminophen (ACOP) and polyethylenimine-functionalized multi-walled carbon nanotubes (PEI- f MWCNT), followed by quantum mechanics studies concerning the oxidation mechanism. Simulations demonstrated that the polymer enhances adsorption by more than 10 kcal mol −1 and that it is important to reproduce the diameter of the nanotube in the simulation models because the adsorption occurs preferentially inside the nanotube. Using square-wave voltammetry (SWV) coupled with a glassy carbon electrode (GCE) surface modified with the dispersion of f MWCNT in the presence of PEI, it was possible to develop an analytical methodology for identification and quantification of ACOP in tablets. The analytical curves were obtained for concentrations of ACOP ranging from 9.99 × 10 −8 to 6.95 × 10 −6 mol L −1 (r = 0.9953). The detection limit and quantification limit of ACOP was determined from SWV and found to be 5.58 × 10 −8 mol L −1 and 1.86 × 10 −7 mol L −1 . The method was successfully applied to real samples detection with the recovery in the range from 95.5% and 111.0% with good stability and reproducibility. Density functional calculations suggested that the oxidation mechanism of ACOP in the presence of the composite may occur in a reversible way, involving H + or H abstraction, in a different path from the metabolic reactions.

This paper describes the development of an electroanalytical procedure proposal for the determination of tricyclic antidepressant imipramine (IMP) in commercial pharmaceutical formulations using boron-doped diamond electrode and square-wave voltammetry. The electrochemical oxidation of imipramine was studied in 0.04 mol L− 1 Britton-Robinson buffer solution. The voltammetric results showed two well-defined oxidation peaks with potentials of 0.04 V and 0.82 V vs. Ag/AgCl/3 mol L− 1 Cl− for peaks 1 and 2, respectively. The effect of the experimental and voltammetric parameters was evaluated and the best performance was obtained in pH 7.4, pulses application frequency of potential of 100 Hz, amplitude of 50 mV and potential increment of 2 mV. Under these conditions, the analytical curves were obtained in the linear range of concentration from 1.73 × 10− 7 mol L− 1 to 2.53 × 10− 6 mol L− 1 (r = 0.9984), with detection and quantitation limits 4.35 × 10− 8 mol L− 1 and 1.45 × 10− 7 mol L− 1, respectively. The proposed method was applied with success in the determination of IMP in commercial pharmaceutical formulations and validated by comparison with standard method for determination of imipramine. The obtained results were in close agreement, at a 95% confidence level, with those obtained using an official method of the British Pharmacopeia.

An analytical methodology for determination of diethylstilbestrol (DES) based on electrochemical response of this compound on glassy carbon electrode modified with gold nanoparticules (AuNPTs), multiwall carbon nanotubes (MWCNTs) and cobalt phtolocyanine (CoPc) was proposed. The modified electrode catalysed the electrochemical oxidation of DES and also improved the sensitivity in comparison with unmodified electrode. The experimental conditions were optimized and also the kinetic electrochemical parameters were also evaluated. From square wave voltammograms, the calibration curve for DES determination were obtained and the calculated detection and quantification limits were equal to 1.99 × 10 −7 mol L −1 and the 6.64 × 10 −7 mol L −1 , respectively. The proposed electroanalytical methodology was successfully applied for DES determination in water, and meat with satisfactory results, showing that fabricated sensor has potential do be applied in laboratory practices for DES determination in complex samples.

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

BiVO4 has been receiving attention for applications in photoelectrochemical devices. This paper describes the effect of different alcohol solvents (ethanol, ethylene-glycol, PEG300 and PEG 400) on the morphology, crystal growth, crystalline size, thickness, photophysical and photoelectrochemical properties of BiVO4 photoanodes prepared from a suitable, simple and inexpensive one-step process. All samples exhibited good crystallinity with the monoclinic phase dominating and with suitable bandgap for visible light harvesting; but the morphology, thickness, and resulting photocurrents varied broadly. The unmodified BiVO4 photoanode prepared with PEG 300, gave a particularly good photocurrent of 0.77 mA cm−2 at 1.23 V vs RHE under illumination of 100 mW cm−2. In this case, a higher value for the ratio between the intensities of the XRD peaks, (040)/(121), was verified, as well as smaller crystallite size. Considering the type of solvent, the BiVO4 photoanode prepared with PEG 300 exhibited a more intense photocurrent. The optimization of the solvent employed in the synthesis of the BiVO4 photoanode is a crucial step in the development of a photoelectrochemical device based on this material.

Here we described the development of a simple methodology for quantification of acetaminophen (ACOP) using square-wave voltammetry (SWV). A glassy carbon electrode modified with gold nanoparticles, functionalized multi-walled carbon nanotubes and cobalt (II) phthalocyanine was prepared and characterized with cyclic voltammetry, SWV and electrochemical impedance spectroscopy. The optimum experimental conditions, such as pH, buffer and square-wave voltammetric parameters were investigated. From the data analysis of the optimization of experimental conditions, the oxidation of ACOP was characterized as a quasi-reversible and proton-dependent process, where the reaction mechanism presents the participation of equal number of protons and electrons (two protons and two electrons) and k s value is equal to 59.0 ± 2.5 s − 1 . Under the optimized conditions, calibration curves were linear in the concentration range of 1.49 μmol L − 1 to 47.6 μmol L − 1 and 47.6 μmol L − 1 to 107.0 μmol L − 1 with a limit of detection of 0.135 μmol L − 1 . Other analytical parameters such as equations of the analytical curves, correlation coefficients, recovery efficiency and relative standard deviation for repeatability and reproducibility experiments were compared to results obtained by the use of UV–Vis spectrophotometry.

The inhibition of laccase enzymatic catalytic activity by formetanate hydrochloride (FMT) was investigated by cyclic voltammetry and by quantum chemical calculations based on density functional theory with a protein fragmentation approach. The cyclic voltammograms were obtained using a biosensor prepared by enzyme immobilization on gold electrodes modified with gold nanoparticles and 4-aminophenol as the target molecule. The decrease in the peak current in the presence of FMT was used to characterize the inhibition process. The calculations identified Asp206 as the most relevant moiety in the interaction of FMT with the laccase enzymatic ligand binding domain. The amino acid residue Cys453 was important, because the Cys453-FMT interaction energy was not affected by the dielectric constant, although it was not a very close residue. This study provides an overview of how FMT inhibits laccase catalytic activity.

This study characterizes the electroanalytical behavior of the carbamate pesticide formetanate hydrochloride (FMT) at a cobalt phthalocyanine (CoPc) functionalized multiwalled carbon nanotubes ( f MWCNT) modified glassy carbon electrode (CoPc- f MWCNT/GCE). Nafion ® was used to improve solubility and dispersibility of f MWCNT. The construction of the developed electrode was characterized by high-resolution field-emission gun scanning electron microscopy, Raman spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. FMT exhibited a behavior consistent with a three-step reaction of the electrochemical-chemical-electrochemical mechanistic type at CoPc- f MWCNT/GCE (three anodic peaks at 0.26, 0.55 and 1.2 V, and two cathodic peaks at 0.35 and 0.50 V vs . Ag/AgCl/3 M KCl). Highly reproducible and well-defined peaks were obtained at the optimum experimental conditions (Britton-Robinson buffer at pH 5.0, accumulation potential 1.55 V, accumulation time 5 s, frequency 100 s −1 , amplitude 30 mV, and scan increment 3 mV). Peak currents were found to be proportional to the FMT concentrations in the range of 9.80 × 10 −8 to 3.92 × 10 −6 mol dm −3 with a detection limit (LOD) of 9.7 × 10 −8 mol dm −3 . The modification of GCE with CoPc- f MWCNT enhanced the electrocatalytic activity and provided high sensitivity (3.51 A mol −1 dm 3 ). The developed electroanalytical methodology was successfully applied to FMT residue analysis in mango and grape samples with recoveries in the range of 94.2 ± 4.5 to 105.7 ± 1.8%. The proposed electroanalytical approach represents a reliable, sensitive and environmental friendly analytical alternative for determination of FMT.

A simple and sensitive photoelectrochemical sensor based on the bismuth vanadate (BiVO4) photoanode coupled to visible light excitation was developed for nitrite detection. The BiVO4 was prepared by hydrothermal methods and used as photoelectroactive sensor. Photoexcitation with visible light allows nitrite anions to act as highly efficient hole scavenger at low potential. The photocurrent response increases linearly with nitrite concentration in the solution. The proposed device operates in the range of detection (2.5 to 100.0 μmol L–1), with limit of detection (1.5 μmol L–1), and with good reproducibility (4.1%) for nitrite analysis. Keywords: Bismuth vanadate, Photoelectrochemical sensor, Nitrite, Hole scavenger

In view of the urgency to replace fossil fuel-based energy sources with sustainable and renewable sources, much has been done to discover new materials and/or production methods that can provide devices capable of converting solar energy into chemical or electrical energy. This work describes the electrodeposition of Bi on WO3 film and its subsequent conversion to BiVO4 with the addition of NH4VO3 and heat treatment. In this way, a WO3/BiVO4 heterojunction is obtained. With this methodology, it is possible to observe the formation of BiVO4 nanostructures with pillar shapes and a photocurrent increase of 300 times compared to films obtained by drop-casting. At 1.23 V vs RHE (Reversible Hydrogen Electrode), the photocurrent achieved with the photoanode reaches 2.1 ± 0.3 mA cm−2, which is 35 times higher than pure BiVO4 and 23 times higher than pure WO3. Transient absorption spectroscopy studies show an increase in the time constants for the recombination of charge carriers to the WO3/BiVO4 heterojunction. Electrodeposition is a relatively simple, easy to use, and scalable technique. So, it is expected that its use for the production of photoelectrodes will be more widespread.

The study describes the electroanalytical approach for benzimidazole pesticide/drug thiabendazole (TBZ) determination using cathodically pretreated boron-diamond doped electrode (BDDE). TBZ exhibited an irreversible oxidation process with peak current and potential values proton-dependent. The TBZH+ that provided the most intense peak current for TBZ oxidation. The reaction mechanism is diffusion-controlled, involving the participation of one electron. The voltammetric and experimental optimized conditions were pH 3.0, potential pulse frequency (f) of 20 s−1, amplitude of the pulse (a) of 20 and the height of the potential step (ΔEs) of 3 mV. The analytical curves were linear from 4.98 × 10−7 to 1.12 × 10−5 mol L−1 with a limit of detection of 1.27 × 10−7 mol L−1. The BDDE was successfully applied to TBZ determination in the several real samples (mango, sugar cane, natural waters and pharmaceutical formulation) with recovery ranged from 71.0 to 103.3% and RSD from 0.91 to 5.3%. The results indicated that the electrochemical methodology based on BDDE presented suitable characteristics in terms of sensitivity, linearity, accuracy and precision.

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.

The influence of functionalized multi-walled carbon nanotubes (fMWCNT) in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) in different ratios was investigated on the acetaminophen (ACOP) electrochemical determination. The electrochemical behavior of the ACOP exhibited a pair of well-defined redox peaks, suggesting that the reversibility of ACOP was significantly improved in comparison to irreversible oxidation peak on bare GCE. The redox process was controlled by adsorption, involves two electrons and the value of apparent rate constant (ks) was equal to 14.7 s-1 ± 3.6 s-1. The analytical curves were obtained for concentrations of ACOP ranging from 0.3 to 3.0 μmol L-1. The values of the detection limit were calculated from SWV and found to be 6.73 × 10-8 mol L-1. The proposed electrochemical sensor exhibited good stability and reproducibility and was applied for ACOP determination in tablets (Tylenol® and Tylenol®DC) with satisfactory results., The authors gratefully acknowledge funding provided by the following Brazilian agencies: CNPq-INCT (Proc. 573925/2008-9 and 573548/2008-0), CAPES/Funcap (2133/2012/Proc. 23038.007973/2012-90), CNPq-PVE (Proc. 400223/2014-7 and 303596/2014-7), PRONEX/FUNCAP (Proc. PR2-0101-00030.01.00/15) and CNPq (Proc. 302801/2014-6). R.N. Gomes thanks CAPES and C.P. Sousa thanks CAPES-PNPD for their grants. The authors also are grateful to the Central Analítica-UFC/CT-INFRA/MCTI-SISNANO/Pró-Equipamentos CAPES for technical support and Prof. Pierre Basílio Almeida Fechine and MsC. Davino Machado Andrade Neto for Zeta potential analysis.

This study describes the development of a simple and accurate methodology for carbamate pesticide formetanate (FMT) analysis in fruits based on the use of a boron-diamond doped electrode (BDDE) cathodically pretreated and on the forward component of the current of square-wave voltammetry (SWV). FMT exhibits a well-defined irreversible oxidation process, which reaction mechanism is diffusion-controlled, involves the participation of one electron and is influenced by the electrolyte pH. However, protonation does not participate in the rate-determining step in the redox process. The optimum experimental and voltammetric conditions were pH 7.0 (0.04 mol L−1 Britton-Robinson buffer), pulse potential frequency of 20 s−1, amplitude of the pulse of 25 mV, and height of the potential step of 3 mV. Under the optimum conditions, calibration curve was linear from 4.98 × 10−7 to 1.70 × 10−5 mol L−1 FMT with a limit of detection of 3.7 × 10−7 mol L−1. FMT sensing was performed in different fruits (mango and grape). Recoveries ranged from 95.2 ± 2.8 to 104.0 ± 3.5% for mango and 96.5 ± 2.5 to 105.2 ± 3.5% for grape proving the accuracy and precision of the electroanalytical methodology. The attained data validated the applicability of the developed approach for FMT quantification in fruits.

This paper describes the use of electrochemical methods and accelerated oxidation experiments (EN 14112, Rancimat method) for the determination of antioxidant activity of phenolic compounds (cardanol, cardol and tert- butylated cardanol) derived from cashew nut shell liquid (CNSL), a byproduct obtained during the processing of cashew nuts classified as a renewable raw material, natural of low-value. Through the electrochemical study, having as reference the anodic peak potential (Epa) and peak current (Ip), was observed that the cardol had the best performance, followed by tert -butylated cardanol and this by cardanol, showing that the presence of electron-donating groups as tert- butyl and hydroxyl exerts a positive influence on the antioxidant action of these compounds. These analyzes showed also that unsaturated compounds presented current values superior than saturated ones, indicating that the unsaturated molecules participate in greater number of the electro-oxidation process. The accelerated oxidation experiments were performed through analysis of biodiesel samples additivated with CNSL-based antioxidants at 500 ppm, and the same sequence of activity presented by the electrochemical study was observed, showing that this class of compounds can be applied effectively to inhibit the oxidative process of biofuel.

The electrochemical behaviour of haloperidol (HP) on hanging mercury dropping (HMDE), silver solid amalgam (p-AgSAE) and mercury-rich solid amalgam (r-AgSAE) electrodes was investigated by cyclic and square-wave voltammetry. Density functional theory (DFT) and Monte Carlo simulations were carried out to explain the electrochemical mechanisms of HP reduction that dominated our measurements. The theoretical explanation of our experimental results was based on the molecular structure and adsorption profile of HP on the surfaces of the electrodes. The calculated LUMO and Hirshfeld's charges pointed to the preferential reduction of HP at the carbonyl group. The most representative DFT-calculated HP adsorption energies on silver, p-AgSAE and HMDE, respectively, were –17.3, –25.9 and –28.6 kcal mol−1. Monte Carlo simulations suggest that HP adsorption is stronger on mercury than on the p-AgSAE surface, explaining the sensitivity order of: p-AgSAE

This work describes the development of an electrochemical enzymatic biosensor for quantification of the pesticide formetanate hydrochloride (FMT). It is based on a gold electrode modified with electrodeposited gold nanoparticles and laccase. The principle behind its development relies on FMT's capacity to inhibit the laccase catalytic reaction that occurs in the presence of phenolic substrates. The optimum values for the relevant experimental variables such as gold nanoparticles electrochemical deposition (at − 0.2 V for 100 s), laccase immobilization ( via glutaraldehyde cross-linking), laccase concentration (12.4 mg/mL), substrate selection and concentration (5.83 × 10 − 5 M of aminophenol), pH (5.0), buffer (Britton–Robinson), and square-wave voltammetric parameters were determined. The developed biosensor was successfully applied to FMT determination in mango and grapes. The attained limit of detection was 9.5 × 10 − 8 ± 9.5 × 10 − 10 M (0.02 ± 2.6 × 10 − 4 mg/kg on a fresh fruit weight basis). Recoveries for the five tested spiking levels ranged from 95.5 ± 2.9 (grapes) to 108.6 ± 2.5% (mango). The results indicated that the proposed device presents suitable characteristics in terms of sensitivity (20.58 ± 0.49 A/μM), linearity (9.43 × 10 − 7 to 1.13 × 10 − 5 M), accuracy, repeatability (RSD of 1.4%), reproducibility (RSD of 1.8%) and stability (19 days) for testing of compliance with established maximum residue limits of FMT in fruits and vegetables.

The electrochemical behaviour and analytical detection procedure for nimesulide (NIM) and ofloxacin (OFX) and their assay in commercial formulations were evaluated using square-wave voltammetry (SWV) combined with a hanging mercury drop electrode (HMDE). All experimental and voltammetric conditions were previously optimized to obtain the best analytical signal in terms of intensities and profile of the reduction peaks. For NIM, the peak currents were related to the one-electron reduction of a nitro group to a stable radical anion, which is followed by a one-electron transfer and a protonation step with a consequent formation of a nitrosoanion. The voltammetric results indicated that the mechanism of OFX involved the transfer of two electrons and two protons in a totally irreversible reduction related to the conversion of a ketone group to an alcohol group. Analytical parameters such as linearity range, equations of the analytical curves, correlation coefficients, detection and quantification limits, recovery efficiency, and relative standard deviation for repeatability and reproducibility experiments were compared to similar results obtained by the use of UV-Vis spectrophotometry, and the results showed that the voltammetric procedure using HMDE is suitable to determine pharmaceutical compounds in complex samples. The applicability of the proposed procedure was tested on pharmaceutical formulations of NIM and OFX by observing the stability, specificity, recovery and precision of the procedure in tablets, oral solution and ophthalmic solution.

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 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 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.

The kinetics and mechanism for electrochemical reduction of haloperidol, a psychotherapeutic drug used in the treatment of schizophrenia, were studied using square wave and cyclic voltammetries allied to a hanging mercury drop electrode. The experimental and voltammetric parameters were optimized at 0.04 mol L −1 Brinton–Robinson buffer (pH 10), with a pulse potential frequency of 100 s −1 , a pulse amplitude of 30 mV and scan increment of 2 mV. Two well-defined peaks were observed, which exhibited properties of fast electron transfer with a strong adsorption process of reactants and products on the electrode surface. The first peak was related to a fast and reversible anion-radical formation originating from the reduction of the carbonyl group, and the second was related to the irreversible reduction of the anion-radical previously formed. Analytical parameters such as: linearity range, equation of the analytical curves, correlation coefficients, detection and quantification limits, recovery efficiency, and relative standard deviation for intraday and interday were compared to similar results obtained by use of the UV–vis spectrophotometry technique, and the analytical results obtained in commercial formulations show that the voltammetric procedure using a hanging mercury drop electrode is suitable for analyzing haloperidol in complex commercial formulation samples.

The electrochemical oxidation of promethazine hydrochloride was made on highly boron-doped diamond electrodes. Cyclic voltammetry experiments showed that the oxidation mechanisms involved the formation of an adsorbed product that is more readily oxidized, producing a new peak with lower potential values whose intensity can be increased by applying the accumulation potential for given times. The parameters were optimized and the highest current intensities were obtained by applying +0.78 V for 30 seconds. The square-wave adsorptive voltammetry results obtained in BR buffer showed two well-defined peaks, dependent on the pH and on the voltammetric parameters. The best responses were obtained at pH 4.0, frequency of 50 s−1, step of 2 mV, and amplitude of 50 mV. Under these conditions, linear responses were obtained for concentrations from 5.96×10−7 to 4.76×10−6 mol L−1, and calculated detection limits of 2.66×10−8 mol L−1 (8.51 μg L−1) for peak 1 and of 4.61×10−8 mol L−1 (14.77 μg L−1) for peak 2. The precision and accuracy were evaluated by repeatability and reproducibility experiments, which yielded values of less than 5.00% for both voltammetric peaks. The applicability of this procedure was tested on commercial formulations of promethazine hydrochloride by observing the stability, specificity, recovery and precision of the procedure in complex samples. All results obtained were compared to recommended procedure by British Pharmacopeia. The voltammetric results indicate that the proposed procedure is stable and sensitive, with good reproducibility even when the accumulation steps involve short times. It is therefore very suitable for the development of the electroanalytical procedure, providing adequate sensitivity and a reliable method.

This work describes the development of a biosensor based on the tyrosinase enzyme (Tyr) for the determination of phenol (PHEN) in laboratory effluent samples derived from ammoniacal nitrogen analysis of the water samples from the Muquém dam in the city of Cariús, CE, using square-wave voltammetry (SWV). The electrode modification consisted of the immobilization of gold nanoparticles, multi-walled carbon nanotubes, cobalt phthalocyanine, and Tyr on a glassy carbon electrode. The electrolyte, pH, enzyme quantity, and voltammetric parameters were optimized to detect PHEN. The analytical curves presented a linear range from 4.97 × 10-6 mol L-1 to 6.10 × 10-5 mol L-1, and the detection limit (DL) and quantitation limit (QL) values were 4.81 × 10-6 mol L-1 and 4.97 × 10-6mol L-1, respectively. The repetition of measurements with the same biosensor and repetition for three other prepared biosensors exhibited a relative standard deviation (RSD) of 5.50 and 1.75%, respectively. The percentage recovery of PHEN in effluent samples varied from 86.40 to 105.04%. The stability of the biosensor was evaluated (at 21 days) with satisfactory results, showing 97.86% of the initial response. Moreover, the DL and recovery percentages agreed with the established values from CONAMA and ABNT, respectively. Thus, the electrode configuration developed seems a promising tool in the detection and quantification of PHEN in complex samples.

This paper reports the electrochemical degradation of the azo dye Ponceau 2R under galvanostatic electrolysis in the 1 to 200 mA cm-2 range at room temperature using dimensionally-stable anodes of oxygen (DSA-O2), chlorine (DSA-Cl2) and a titanium electrode of platinum coated with platinum oxide (Ti/Pt). The methodology applied was efficient for removing the color of the Ponceau 2R and the highest percentage removal of total organic carbon was obtained at 200 mA cm-2. Despite not having been observed complete mineralization, approximately80% removal of aromatic rings was estimated, resulting in drastic reduction of toxicity of the sample.

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.