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In this study, we introduce a novel electrochemical sensor combining reduced graphene oxide (rGO) sheets with a bismuth–mercury (Bi/Hg) film, electroplated onto pencil graphite electrodes (PGEs) for the high-sensitivity detection of trace amounts of gallium (Ga3+) and indium (In3+) in water samples using square wave anodic stripping voltammetry (SWASV). The electrochemical modification of PGEs with rGO and bimetallic Bi/Hg films (ERGO-Bi/HgF-PGE) exhibited synergistic effects, enhancing the oxidation signals of Ga and In. Graphene oxide (GO) was accumulated onto PGEs and reduced through cyclic reduction. Key parameters influencing the electroanalytical performance, such as deposition potential, deposition time, and pH, were systematically optimized. The improved adsorption of Ga3+ and In3+ ions at the Bi/Hg films on the graphene-functionalized electrodes during the preconcentration step significantly enhanced sensitivity, achieving detection limits of 2.53 nmol L−1 for Ga3+ and 7.27 nmol L−1 for In3+. The preferential accumulation of each post-transition metal, used in transparent displays, to form fused alloys at Bi and Hg films, respectively, is highlighted. The sensor demonstrated effective quantification of Ga3+ and In3+ in tap water, with detection capabilities well below the USEPA guidelines. This study pioneers the use of bimetallic films to selectively and simultaneously detect the post-transition metals In3+ and Ga3+, highlighting the role of graphene functionalization in augmenting metal film accumulation on cost-effective graphite rods. Additionally, the combined synergistic effects of Bi/Hg and graphene functionalization have been explored for the first time, offering promising implications for environmental analysis and water quality monitoring. [ABSTRACT FROM AUTHOR]

Screen-printed electrodes (SPEs) are reliable, portable, affordable, and versatile electrochemical platforms for the real-time analytical monitoring of emerging analytes in the environmental, clinical, and agricultural fields. The aim of this study was to evaluate the electrochemical behavior of gold screen-printed electrodes (SPGEs) modified with molecules containing amino (Tr-N) or α-aminophosphonate (Tr-P) groups for the selective and sensitive detection of the toxic metal ions Pb2+ and Hg2+ in aqueous samples. After optimizing the analytical parameters (conditioning potential and time, deposition potential and time, pH and concentration of the supporting electrolyte), anodic square wave stripping voltammetry (SWASV) was used to evaluate and compare the electrochemical performance of bare or modified electrodes for the detection of Hg2+ and Pb2+, either alone or in their mixtures in the concentration range between 1 nM and 10 nM. A significative improvement in the detection ability of Pb2+ ions was recorded for the amino-functionalized gold sensor SPGE-N, while the presence of a phosphonate moiety in SPGE-P led to greater sensitivity towards Hg2+ ions. The developed sensors allow the detection of Pb2+ and Hg2+ with a limit of detection (LOD) of 0.41 nM and 35 pM, respectively, below the legal limits for these heavy metal ions in drinking water or food, while the sensitivity was 5.84 µA nM−1cm−2 and 10 µA nM−1cm−2, respectively, for Pb2+ and Hg2+. The reported results are promising for the development of advanced devices for the in situ and cost-effective monitoring of heavy metals, even in trace amounts, in water resources. [ABSTRACT FROM AUTHOR]

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance. [ABSTRACT FROM AUTHOR]

In the framework of deep penetrating geochemistry for mineral exploration, we report a field electroanalytical method using disposable screen-printed working electrodes able to quantify metal pathfinders in partial extracts of soil samples at the nanomolar level on-site. Four metal pathfinders (Co, Ni, Pb and Zn) were chosen due to their geological interest and suitability of electrochemical detection. Square-wave anodic stripping voltammetry (SW-ASV) was developed for the simultaneous detection of Pb(II) and Zn(II) providing limits of detection (LOD) of 1.2 and 5.3 nM, respectively. A linear-scan cathodic stripping voltammetry (LS-CSV) methodology was developed for the joint detection of Co(II) and Ni(II) yielding LOD of 1.8 and 3.5 nM, respectively. Method validation was carried out on 14 upper B-horizon soil samples during a field survey. Two wet extraction procedures were applied for soil samples – a strong extraction using nitric acid (HNO3) and a weak extraction using calcium chloride (CaCl2). Excellent agreement between electroanalytical methods and inductively coupled plasma mass spectrometry (ICP-MS) was found for Pb(II), while a small underestimation was observed for Zn(II). For Co(II) and Ni(II) the LS-CSV measurements in the HNO3 extractions were impossible due to the change from low pH to pH to 7.15 which induces precipitation of iron and aluminium. For the CaCl2 extractions, the Co(II)/Ni(II) results obtained by LS-CSV were in excellent agreement with ICP-MS measurements. [ABSTRACT FROM AUTHOR]

The electroanalytical methods have been developed for wide application, especially for trace metal ions. In this study, the applicability of 1-butyl- -3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) ionic liquid as a pasting binder to fabricate a multi-walled carbon nanotube paste electrode (MWCNT PE) for detecting Pb2+ and Cd2+ was evaluated. The electrochemical properties of electrodes were explored by cyclic voltammetry, electrochemical impedance spectroscopy and linear sweep anodic stripping voltammetry. The use of [BMIm][PF6] alone as a conductive binder resulted in an electrode that was unsatisfactory for electrochemical analysis. However, the MWCNT PE with the pasting mixture of silicon oil and [BMIm][PF6] displayed excellent sensitivity for the Pb2+ and Cd2+ determinations, with limits of detection of 2.25 and 1.59 g L-1, respectively. The proposed electrode was demonstrated to be a reliable sensor for accurately quantifying trace amounts of Pb2+ and Cd2+, exhibiting good repeatability, reproducibility and stability.

In this study, we introduce a novel electrochemical sensor combining reduced graphene oxide (rGO) sheets with a bismuth–mercury (Bi/Hg) film, electroplated onto pencil graphite electrodes (PGEs) for the high-sensitivity detection of trace amounts of gallium (Ga3+) and indium (In3+) in water samples using square wave anodic stripping voltammetry (SWASV). The electrochemical modification of PGEs with rGO and bimetallic Bi/Hg films (ERGO-Bi/HgF-PGE) exhibited synergistic effects, enhancing the oxidation signals of Ga and In. Graphene oxide (GO) was accumulated onto PGEs and reduced through cyclic reduction. Key parameters influencing the electroanalytical performance, such as deposition potential, deposition time, and pH, were systematically optimized. The improved adsorption of Ga3+ and In3+ ions at the Bi/Hg films on the graphene-functionalized electrodes during the preconcentration step significantly enhanced sensitivity, achieving detection limits of 2.53 nmol L−1 for Ga3+ and 7.27 nmol L−1 for In3+. The preferential accumulation of each post-transition metal, used in transparent displays, to form fused alloys at Bi and Hg films, respectively, is highlighted. The sensor demonstrated effective quantification of Ga3+ and In3+ in tap water, with detection capabilities well below the USEPA guidelines. This study pioneers the use of bimetallic films to selectively and simultaneously detect the post-transition metals In3+ and Ga3+, highlighting the role of graphene functionalization in augmenting metal film accumulation on cost-effective graphite rods. Additionally, the combined synergistic effects of Bi/Hg and graphene functionalization have been explored for the first time, offering promising implications for environmental analysis and water quality monitoring.

This article presents a new working electrode based on a bismuth-plated, gold-based microelectrode array, which is suitable for determining thallium(I) species using anodic stripping voltammetry (ASV). It allowed a significant increase in the sensitivity as compared to other voltammetric sensors. The main experimental conditions and the instrumental parameters were optimized. A very good proportionality between the Tl(I) peak current and its concentration was evidenced in the range from 5 × 10−10 up to 5 × 10−7 mol L−1 (R = 0.9989) for 120 s of deposition and from 2 × 10−10 up to 2 × 10−7 mol L−1 (R = 0.9988) for 180 s. A limit of detection (LOD) of 8 × 10−11 mol L−1 for a deposition time of 180 s was calculated. The effects of interfering ions on the Tl(I) analytical signal were studied. The proposed method was applied for quantitative Tl(I) detection in water certified reference material TM 25.5 as well as in spiked real water samples, for which satisfactory recovery values between 98.7 and 101.8% were determined. [ABSTRACT FROM AUTHOR]

The anodic stripping voltammetry method for determining trace cadmium is a classic fundamental experiment in instrumental analysis. However, the traditional teaching content of this experiment is difficult for students to appreciate the value of their acquired knowledge in practical industry and life, which fails to effectively meet the requirements for integrating ideological and political education into the course. Herein, we propose an innovative design and optimization approach for the experiment, better facilitating educational goals of curricular ideological and political education. It involves inspiring students to research and discuss recent news events, the history of the discipline, stories of scientists, and the latest trends in the industry. Additionally, design-oriented and exploratory elements are incorporated into the experiment, which improves the high-level nature of the course. Instead of using pre-prepared cadmium solutions, real-world samples like purchased rice and other grains are used. Furthermore, students independently prepare mercury film electrodes suitable for electrochemical workstations, replacing commercially available electrodes used directly in polarographs. This allows students to not only strengthen their practical skills but also understand the development and modification of analytical instruments and grasp fundamental research paradigms in analytical chemistry. The aforementioned optimizations of this experiment will help to cultivate students’ scientific spirit and research aptitude, nurture them with the significance of academic knowledge in solving practical problems in the industry and life, and assist them in establishing professional goals and fostering a sense of social responsibility. [ABSTRACT FROM AUTHOR]

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance.

The monitoring of toxic contaminant traces in the environment needs a simple and sensitive method, such as stripping analysis that applies a pre-concentration step to the analyte on the working electrode. The present work focuses on the realization of a two-electrode sensor made by means of laser-induced graphitization of a polyimide (PI) tape. Moreover, taking advantage of the strong affinity of Bi for metal ions for detection by Anodic Stripping Voltammetry (ASV), the proposed sensor implementation involved the use of Bi2O3 nanopowder as the precursor of Bi film as eco-friendly Hg substitute. Physicochemical analyses were conducted to investigate elemental and structural differences in relation to the shifts recorded in the voltametric behavior. [ABSTRACT FROM AUTHOR]

The detection of trace heavy metal ions is important in monitoring water quality, a vital freshwater source. This study presents the preparation of a multi-walled carbon nanotube (MWCNTs) paste electrode using a pasting mixture of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid ([Bmim][PF6] IL) and paraffin oil for the determination of Cd2+ and Pb2+. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy were applied to characterize the paste composites. The electrochemical behavior of the fabricated electrodes was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The [Bmim][PF6]-MWCNTs electrode showed enhanced sensitivity for Cd2+ and Pb2+ detections over linear sweep anodic stripping voltammetry (LSASV) performances. Experimental results showed that the MWCNTs-IL-1 electrode using a pasting mixture of 10 μL of [Bmim][PF6] and 190 μL of paraffin oil was the most suitable for Cd2+ and Pb2+ determinations. The LSASV conditions for Cd2+ and Pb2+ analysis at the MWCNTs-IL-1 electrode were optimized, including the deposition potential, deposition time, and pH of the working solution. The stripping peak currents were linearly correlated with the concentration ranges of Cd2+ (1–35 μg/L) and Pb2+ (1–90 μg/L) for both individual and simultaneous determinations. The MWCNTs-IL-1 electrode exhibited high repeatability, reproducibility, and stability over a 30-day storage period. The real applicability of the MWCNTs-IL-1 electrode was demonstrated by successful determinations of Cd2+ and Pb2+ concentrations in tap water and surface water samples, which agreed with the results obtained by inductively coupled plasma mass spectrometry.

The integration of sensing devices into cell culture systems is a topic of great interest in the study of pathologies and complex biological mechanisms in real-time. In particular, the fit-for-purpose microfluidic devices called organ-on-chip (OoC), which host living engineered organs that mimic in vivo conditions, benefit greatly from the integration of sensors, enabling the monitoring of specific chemical-physical parameters that can be correlated with biological processes. In this context, copper is an essential trace element whose total concentration may be associated with specific pathologies, and it is therefore important to develop reliable analytical techniques in cell systems. Copper can be determined by using the anodic stripping voltammetry (ASV) technique, but its applicability in cell culture media presents several challenges. Therefore, in this work, the performance of ASV in cell culture media was evaluated, and an acidification protocol was tested to improve the voltammetric signal intensity. A Transwell® culture model with Caco-2 cells was used to test the applicability of the developed acidification protocol by performing an off-line measurement. Finally, a microfluidic device was designed in order to perform the acidification of the cell culture medium in an automated manner and then integrated with a silicon microelectrode to perform in situ measurements. The resulting sensor-integrated microfluidic chip could be used to monitor the concentration of copper or other ions concentration in an organ-on-chip model; these functionalities represent a great opportunity for the non-destructive strategic experiments required on biological systems under conditions close to those in vivo. [ABSTRACT FROM AUTHOR]

The potential reach of point-of-care (POC) diagnostics into daily routines for exposure to reactive oxygen species (ROS) and Cu in aerosolized particulate matter (PM) demands that microfluidic paper-based analytical devices (μPADs) take into consideration the simple detection of these toxic PM components. Here, we propose μPADs with a dual-detection system for simultaneous ROS and Cu(II) detection. For colorimetric ROS detection, the glutathione (GSH) assay with a folding design to delay the reaction yielded complete ROS and GSH oxidation, and improved homogeneity of color development relative to using the lateral flow pattern. For electrochemical Cu(II) determination, 1,10-phenanthroline/Nafion modified graphene screen-printed electrodes showed ability to detect Cu(II) down to pg level being low enough to be applied to PM analysis. No intra- and inter-interference affecting both systems were found. The proposed μPADs obtained LODs for 1,4-naphthoquinone (1,4-NQ), used as the ROS representative, and Cu(II) of 8.3 ng and 3.6 pg, respectively and linear working ranges of 20 to 500 ng for ROS and 1 × 10−2 to 2 × 102 ng for Cu(II). Recovery of the method was between 81.4 and 108.3% for ROS and 80.5–105.3% for Cu(II). Finally, the sensors were utilized for simultaneous ROS and Cu(II) determination in PM samples and the results statistically agreed with those using the conventional methods at 95% confidence. [ABSTRACT FROM AUTHOR]

This research has successfully created a carbon paste electrode that has been modified with nitrogen-sulfur-doped graphene oxide, allowing for the accurate detection of chromium ions in aqueous solutions. The surface morphology of the modifier was investigated by FT-IR and SEM. Through the use of anodic stripping differential pulse voltammetry, the electrochemical response of the modified carbon paste electrode to chromium ions has been analyzed and shown to exhibit an excellent electro-oxidation response when exposed to chromium ions. The linear dynamic range of chromium analysis produced a remarkable sensitivity of 0.1986 between 0.01 and 10 nM, with a sensitivity of 0.2048 between 10 and 125 nM. The detection limit was found to be 4.58 pico-molar. In a real sample, the electrode was able to measure chrome (VI) with results comparable to other techniques used in measuring chrome (VI). This achievement highlights the possibilities of utilizing innovative technology to create solutions that can address real-world problems. [ABSTRACT FROM AUTHOR]

Rapid screening of individuals infected with severe acute respiratory syndrome‐coronavirus‐2 (SARS‐CoV‐2) is necessary to contain contagion in a large population. Nucleic acid‐based gold standard assays are time‐consuming, and nucleic acid amplification is mandatory and expensive, impeding the containment of the coronavirus disease 2019 (COVID‐19) outbreak. To overcome the aforementioned disadvantages, this study deals with a specially designed gold (Au)‐deoxyribonucleic acid (DNA)‐cadmium telluride (CdTe) quantum dot (QD) probe to target two sections of the nucleocapsid (N) gene of SARS‐CoV‐2 ribonucleic acid (RNA) of three variants (B.1.1.529, B.1.617.2, and B.1.351). A duplex‐specific nuclease (DSN)‐assisted highly selective release of signaling probes enable higher specificity, and an Au‐supported DNA probe is incorporated to carry many CdTe QD signaling probes. After dissolution, the generated Cd2+ ions are quantified at the novel cobalt sulfide (CoS)‐nitrogen‐doped graphene QD (NGQD)/platinum (Pt)@palladium (Pd) electrode with extraordinary sensitivity through square wave anodic stripping voltammetry (SWASV). The developed sensor exhibits a wide range of detection (10 to 108 copies µL−1) and a lower detection limit (0.12 copies µL−1), without any amplification. The selectivity of the sensor is tested against MERS and HCoV‐NL63, and real‐time detection is performed on heat‐inactivated viral samples, which show excellent selectivity. [ABSTRACT FROM AUTHOR]

Electrochemical detection, especially anodic stripping voltammetry (ASV), has been widely used in the detection of heavy metal ions because of its high sensitivity, low detection limit, as well as on-site and real-time detection capability. However, ASV detection typically relies on modified sensors, which complicates the preparation process and introduces contaminants to the tested solutions. Herein, we developed a preconcentration relaxation strategy to improve detection performances of bare sensors without modification. Specifically, in the preconcentration step of ASV, the solution stirring did not run throughout the whole preconcentration process but stopped before the end of preconcentration, remaining as a relaxation period for metal ions fully depositing. To verify this strategy, we fabricated porous laser-induced graphene sensors without modification to detect lead ions. With the preconcentration strategy, the detection linear range was widened from 30–100 to 1–100 μg·L–1, and the sensitivity was increased from 0.1362 μA·(μg·L–1)−1 to 0.1772 μA·(μg·L–1)−1 in 1–5 μg·L–1 and 0.7081 μA·(μg·L–1)−1 in 10–100 μg·L–1. Moreover, the limit of detection reached 0.5 μg·L–1 (S/N = 3). This work sheds light on the accurate and effective detection of heavy metal ions. [ABSTRACT FROM AUTHOR]

In developing countries, subsistence gold mining entails mixing metallic mercury with crushed sediments to extract gold. In this approach, the gold−mercury amalgam is heated to evaporate mercury and obtain gold. Thus, the highly volatile mercury can be absorbed through inhalation, resulting in adverse health effects. Urinalysis can be used to detect mercury, which is excreted in urine and feces, and correlate exposure with toxic effects. The current gold standard analytical methods are based on fluorescence or inductively coupled plasma mass spectrometry methods, but are expensive, time consuming, and are not easily accessible in countries where testing is needed. In this work, we report on a miniature electrochemical sensor that can rapidly detect mercury in urine at levels well below the US Biological Exposure Index (BEI) limit of 50 ppb (μg/L). The sensor is based on a thin‐film gold electrode and anodic stripping voltammetry electroanalytical approach. The sensor successfully detected mercury at trace levels in urine, with a limit of detection of ∼15 ppb Hg in the linear range of 20–80 ppb. With the low‐cost disposable sensors and portable instrumentation, it is well suited for point‐of‐care applications. [ABSTRACT FROM AUTHOR]

Monitoring of ions in real-time directly in cell culture systems and in organ-on-a-chip platforms represents a significant investigation tool to understand ion regulation and distribution in the body and ions' involvement in biological mechanisms and specific pathologies. Innovative flexible sensors coupling electrochemical stripping analysis (square wave anodic stripping voltammetry, SWASV) with an ion selective membrane (ISM) were developed and integrated in Transwell™ cell culture systems to investigate the transport of zinc and copper ions across a human intestinal Caco-2 cell monolayer. The fabricated ion-selective sensors demonstrated good sensitivity (1 × 10−11 M ion concentration) and low detection limits, consistent with pathophysiological cellular concentration ranges. A non-invasive electrochemical impedance spectroscopy (EIS) analysis, in situ, across a selected spectrum of frequencies (10–105 Hz), and an equivalent circuit fitting were employed to obtain useful electrical parameters for cellular barrier integrity monitoring. Transepithelial electrical resistance (TEER) data and immunofluorescent images were used to validate the intestinal epithelial integrity and the permeability enhancer effect of ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) treatment. The proposed devices represent a real prospective tool for monitoring cellular and molecular events and for studies on gut metabolism/permeability. They will enable a rapid integration of these sensors into gut-on-chip systems. [ABSTRACT FROM AUTHOR]

Electrochemistry has the advantages of low detection limit, high sensitivity, short analysis time, and convenient operation. It is an effective method for rapid detection of heavy metal ions in environmental samples. In this paper, humic acid-based activated carbon was prepared by chemical activation of humic acid extracted from lignite. The carbon paste electrode was doped with humic acid-based activated carbon, and the stripping voltammetry characteristics of Cd(Ⅱ) on the modified electrode were studied by anodic stripping voltammetry. The research shows that the doping of humic acid-based activated carbon on carbon paste electrode improved the response of Cd(Ⅱ) on the electrode, thus improving the sensitivity, expanding the linear detection range, and reducing the detection limit. When the activated carbon was used for chemical modification of carbon paste electrode a high content of oxygen-containing functional groups and a large pore size, were beneficial to improving the response of Cd(Ⅱ) on the electrode and improving the sensitivity of the electrode. All the carbon paste electrodes doped by humic acid-based activated carbon exhibited good repeatability and long-term stability.

The great performance of nanostructured hydroxyapatite (Hap) in adsorbing heavy metal cations with the good electrical conductivity of high‐surface carbon materials was here combined for the crafting of high‐content hydroxyapatite electrodes (Hap 84–96 wt.%) endowed with the synergistic capability of detection and adsorption of heavy metal cations by water solutions. To improve the sustainability of the sensor, a mesoporous carbon (derivable by bio‐waste) was selected as scaffold for depositing Hap by simply co‐precipitation. The composite with 92 wt.% of Hap, which exhibited ca. 1 : 1 ratio between the exposed area of Hap and carbon (by Brunauer‐Emmett‐Teller method), invariably showed an average stripping oxidation peak intensity of ca. 250 μA cm−2 and 150 μA cm−2 for a 50 μM Pb2+ and Cu2+ solution, respectively. Control experiments showed that the above sensor outperformed the sensibility of two low‐content Hap electrodes (4 and 8 wt.%), representative of the best performing Hap‐carbon composites available in literature. [ABSTRACT FROM AUTHOR]

Nowadays people are becoming poisoned through the consumption of herbal remedies that comprise heavy metals (HMs) worldwide. It is possible for HMs to be present in pharmaceutical herb materials coming from anthropogenic activities like agriculture, industrial waste, and natural sources. In various ethnic groups, there is evidence that contaminants were purposefully added in the belief that they had some sort of therapeutic benefit. HM toxicity of medicinal plant products has been linked to a wide range of adverse health effects, causing dysfunction of the liver, kidney, and heart, and even death. Natural plant-based products established around the world have progressed to the point that they now combine a variety of synthetic products for their purported medical benefits. This assessment focuses on the impacts of HMs on plants, sources of HMs, herbal sample collection, and identification techniques, especially in medicinal plant samples. At the same time, it focuses on the sociocultural applications of HMs as well as the dangers associated with their usage in conventional therapies. It is necessary to implement appropriate regulation and monitoring systems for natural supplements due to the prevalence of hazardous HMs. [ABSTRACT FROM AUTHOR]

In this work, a “green” electrochemical paper-based device (ePAD) for the voltammetric determination of Tl(I) is described. A mini voltammetric cell was patterned on chromatographic paper by using screen printing to deposit three carbon electrodes and plotting with hydrophobic ink to form a circular assay zone. The sample was added to the assay zone (which was pre-loaded with Bi(III)) and Tl(I) was quantified using anodic stripping voltammetry (ASV). The experimental conditions and potential interferences were studied. The limit of detection was at the low μg L−1 level, indicating that these devices can serve successfully as fit-for-purpose disposable voltammetric sensors for Tl(I).

3D-carbon nanomaterials have proven to be high-performance transducers in electrochemical sensors but their integration into miniaturized devices is challenging. Herein, we develop printable freestanding laser-induced carbon nanofibers (f-LCNFs) with outstanding analytical performance that furthermore can easily allow such miniaturization through a paper-based microfluidic strategy. The f-LCNF electrodes were generated from electrospun polyimide nanofibers and one-step laser carbonization. A three-electrode system made of f-LCNFs exhibited a limit of detection (LOD) as low as 1 nM (S/N = 8) for anodic stripping analysis of silver ions, exhibiting the peak at ca. 100 mV vs f-LCNFs RE, without the need of stirring. The as-described system was implemented in miniaturized devices via wax-based printing, in which their electroanalytical performance was characterized for both outer- and inner-sphere redox markers and then applied to the detection of dopamine (the peak appeared at ca. 200 mV vs f-LCNFs RE) with a remarkable LOD of 55 pM. When modified with Nafion, the f-LCNFs were highly selective to dopamine even against high concentrations of uric and ascorbic acids. Especially the integration into closed microfluidic systems highlights the strength 3D porous structures provides excellent analytical performance paving the way for their translation to affordable lab-on-a-chip devices where mass-production capability, unsophisticated fabrication techniques, transfer-free, and customized electrode designs can be realized. [ABSTRACT FROM AUTHOR]

The integration of sensing devices into cell culture systems is a topic of great interest in the study of pathologies and complex biological mechanisms in real-time. In particular, the fit-for-purpose microfluidic devices called organ-on-chip (OoC), which host living engineered organs that mimic in vivo conditions, benefit greatly from the integration of sensors, enabling the monitoring of specific chemical-physical parameters that can be correlated with biological processes. In this context, copper is an essential trace element whose total concentration may be associated with specific pathologies, and it is therefore important to develop reliable analytical techniques in cell systems. Copper can be determined by using the anodic stripping voltammetry (ASV) technique, but its applicability in cell culture media presents several challenges. Therefore, in this work, the performance of ASV in cell culture media was evaluated, and an acidification protocol was tested to improve the voltammetric signal intensity. A Transwell® culture model with Caco-2 cells was used to test the applicability of the developed acidification protocol by performing an off-line measurement. Finally, a microfluidic device was designed in order to perform the acidification of the cell culture medium in an automated manner and then integrated with a silicon microelectrode to perform in situ measurements. The resulting sensor-integrated microfluidic chip could be used to monitor the concentration of copper or other ions concentration in an organ-on-chip model; these functionalities represent a great opportunity for the non-destructive strategic experiments required on biological systems under conditions close to those in vivo.

An effective electrochemical sensor was developed to detect and determine of the As(III) by modifying the carbon paste electrode (CPE) with graphitic carbon nitride decorated with iron-based metal-organic frameworks (Fe-MOF/g-C 3 N 5). The differential pulse anodic stripping voltammetry (DPASV) method was used to analyze As(III) ions in a phosphate buffer solution (0.10 M, pH = 5). Fe-MOF/g-C 3 N 5 /CPE showed high sensitivity (4.24 μA μg−1 L), satisfactory linear range (0.50 μg L−1–5.00 μg L−1 and 5.00 μg L−1–30.00 μg L−1), and low detection limit (LOD, 0.013 μg L−1). The prepared sensor was showed an excellent repeatability and selectivity, and successfully used for determination of the As(III) ion in ambient waters and apple juice samples. • A Fe-MOF/g-C 3 N 5 nanocomposite was synthesized through the solvothermal method. • Fe-MOF/g-C3N5 was used to modify carbon paste as an electrochemical sensor. • The prepared sensor showed excellent sensitivity for As (III) analysis. • The sensor was successfully used for determination of the As (III) ion in water samples. [ABSTRACT FROM AUTHOR]

The fabrication of fully ink-drawn fluidic electrochemical paper-based analytical devices (ePADs) is reported for the determination of trace Pb(II) and Cd(II) by differential pulse anodic stripping voltammetry (DPASV). The fluidic pattern was formed on the paper substrate using an inexpensive computer-controlled x–y plotter and a commercial hydrophobic marker pen. Then, electrodes were deposited on the devices using a second x–y plotting step with a commercial technical pen filled with a graphite-based conductive ink prepared in house. The fabrication parameters of the ePADs were studied by cyclic voltammetry using the ferro/ferri couple as a probe and by scanning electron microscopy. The ePADs, featuring a bismuth nanoparticle-modified working electrode, were applied to the determination of Pb(II) and Cd(II) by DPASV. The chemical and instrumental conditions were studied. The limits of detection were 3.1 μg L−1 for Cd(II) and 4.5 μg L−1 for Pb(II) whereas the between-device reproducibility (expressed as the % relative standard deviation of the response at 6 different ePADs) was < 14%. Each ePAD requires 120 s to fabricate and costs less than 0.15 € in terms of consumables. The ePADs are suitable for the on-site determination of Pb(II) and Cd(II) in environmental and food samples. [ABSTRACT FROM AUTHOR]

Dyes are generally defined as an aromatic organic compound which shows an affinity towards the substrate to which they are being applied. The presence of dyes in wastewater samples at any level is not safe for human. The presence of dyes in wastewater that being discharged from fabrics industry must be analyzed. Hence, a sensitive, precise, rapid, accurate, simple and low-cost analytical method is needed for dyes determination. The differential pulse anodic stripping voltammetric (DPASV) technique using glassy carbon electrode (GCE) as a working electrode and phosphate buffer at pH 4.2 as a supporting electrolyte has been proposed. The experimental voltammetric parameters were optimized in order to obtain a maximum response with analytical validation of the proposed technique. The optimum parameters were initial potential (Ei) = +0.3 V, end potential (Ef) = +1.0 V, scan rate (v) = 0.04 V/s, accumulation time (tacc) = 50 s, accumulation potential (Eacc) = 0.4 V and pulse amplitude = 0.075 V. The anodic peak was appeared at 0.77972 V. The curve was linear from 0.5 to 1.25 mg/L (R2=0.9986) with detection limit of 0.050 mg/L. The precisions in terms of relative standard deviation (RSD) were 0.08 %, 0.62 % and 0.50 % for consecutive three days. The range recovery achieved for 0.5, 0.7 and 1.0 mg/L of RB5 standard solution in simulation dye sample was 104.40 %, 89.71 %, and 111.15 %, respectively. It can be concluded that the proposed technique is precise, accurate, rugged, low cost, fast and has potential to be an alternative method for routine analysis of RB5. The proposed method will be tested for the content of RB5 dye in the real wastewater samples from fabric industry.

This manuscript investigates the chemical and structural stability of 3D printing materials (3DPMs) frequently used in electrochemistry. Four 3D printing materials were studied: Clear photopolymer, Elastic photopolymer, PET filament, and PLA filament. Their stability, solubility, structural changes, flexibility, hardness, and color changes were investigated after exposure to selected organic solvents and supporting electrolytes. Furthermore, the available potential windows and behavior of redox probes in selected supporting electrolytes were investigated before and after the exposure of the 3D-printed objects to the electrolytes at various working electrodes. Possible electrochemically active interferences with an origin from the 3DPMs were also monitored to provide a comprehensive outline for the use of 3DPMs in electrochemical platform manufacturing. [ABSTRACT FROM AUTHOR]

Herein, a new catalyst is prepared by covalent functionalization of graphene quantum dot with D-penicillamine (GQD-DPA). The successful functionalization and synthesis of GQD-DPA approved by different characterization methods and resultant GQD-DPA applied as an electrode modifier for preparation of Pb2+ electrochemical sensor. The GQD-DPA-modified glassy carbon electrode (GQD-DPA/GCE) displays a meaningful improved sensitivity and selectivity for Pb2+ which is possibly due to the increased surface area in addition to the presence of functional groups on its structure. Under optimum conditions, GQD-DPA/GCE shows linear behavior to Pb2+ determination in the concentration range from 0.03 to 2.8 nM with 0.01 nM as calculated detection limit. The GQD-DPA/GCE exhibits interference-free behavior in the measurement of Pb2+ ions. The prepared sensor is used for the determination of Pb2+ ions in tap water and river water samples with high accuracy and precision. [ABSTRACT FROM AUTHOR]

Contamination of natural water by mercury (Hg2+) and bismuth (Bi3+) metal ions have been extensively studied due to their toxic effects. A validated square‐wave anodic stripping voltammetry (SW‐ASV) method for determining Bi3+ and Hg2+ ions individually and simultaneously is described. A new electrochemical sensor was constructed using a gold (Au) electrode that has been modified with poly(1,2‐diaminoanthraquinone) (p‐1,2‐DAAQ). Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were used to characterize the p‐1,2‐DAAQ/Au modified electrode. Factors such as the polymer film thickness, electrolyte, square wave parameters and preconcentration conditions were optimized to improve the performance of the modified Au electrode. Good linear responses were achieved in the concentration ranges of 1–200 μg L−1 and 1–50 μg L−1 forBi3+ and Hg2+, respectively, and the limits of detection were 0.27 μg L−1 (Bi3+) and 0.29 μg L−1 (Hg2+). The interference study results illustrated the high selectivity of the modified electrode for detection of Bi3+ and Hg2+. The proposed SW‐ASV method was successfully applied for Bi3+ and Hg2+analyses in different real water samples. [ABSTRACT FROM AUTHOR]

Heavy metals are materials with many advantages. However, it is also harmful to the environment and human health. Lead and cadmium can cause many health problems, such as cancer, liver dysfunction, nervous system disorders, cardiovascular problems, and many more. Lead and cadmium can also accumulate in water, soil, and plants. Based on the problem, the development of lead and cadmium analytical methods was necessary to monitor its concentration level in the environment. One of heavy metal analysis's widest voltammetry methods is anodic stripping voltammetry (ASV). ASV involves the accumulation and stripping step to improve the analysis sensitivity toward heavy metals ions. ASV applied a threeelectrode system and the working electrode played an essential role in obtaining an excellent analysis performance. Recently, bismuth-material was widely used for a working electrode in voltammetry methods, especially heavy metals analysis. Bismuth can form alloys with lead and cadmium ions during the deposition step in ASV and improve sensitivity. Bismuth also has low toxicity than mercury. Therefore, this review described the recent development of bismuth-based electrodes and their modification with other materials. We also briefly explained the ASV principle and its important parameter that needs optimization. In several previous studies, the modification of bismuth-based electrodes with various materials, such as carbon nanomaterials, conductive polymers, and metal nanoparticles, can give a synergic effect and enhancement the performance of lead and cadmium analysis. [ABSTRACT FROM AUTHOR]

Oxidation behavior of tretinoin (TRN) was evaluated using anodic stripping voltammetry (ASV), differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques in Britton-Robinson (B-R) pH 7. The glassy carbon (GC) electrode was used to deposit the compound (TRN) into its surface to record a well-defined oxidation peak at 0.75 V in the presence of Ag/AgCl reference electrode and a Pt counter electrode. Some analytical parameters were studied to obtain the best oxidation signal, for example; buffer solution, pH, accumulation potential and time, amplitude, frequency, scan rate and convection rate. The high sensitivity anodic peak was obtained using B-R, pH 7, 40 s accumulation time, −0.6 V accumulation potential, 50 mV amplitude, 20 Hz frequency, 350 mV s−1 scan rate, and 1000 rpm. These parameters were chosen as optimum conditions for the continued experiments. The analytical performance of the used technique was evaluated using the study of repeatability, stability, recovery, calibration curve and detection limit. Repeatability and stability was monitored for 5 × 10−6 mol L−1 of TRN to give 0.24% relative standard deviation (RSD%) for eighth anodic measurements, while the stability was been very well for 80 min. The calibration curve was studied over the range of 1 × 10−6–1 × 10−5 mol L−1 (n = 6), yielded, a linear relationship between concentrations and anodic current for TRN. A detection limit (LOD) was calculated to be 7.5 × 10−9 mol L−1 (2.25 ppb), while a quantification limit (LOQ) was yielded 2.49 × 10−8 mol L−1 (7.47 ppb). Anodic stripping voltammetry method was developed and applied for the determination of TRN in the human urine and plasma samples.

In this study, gold nanoparticles AuNPs were deposited onto graphene oxide GO modified pencil graphite electrode PGE in order to construct a disposable sensor platform for the electrochemical detection of ceftizoxime CFX . Initially, electrode surface was covered with GO by physical adsorption and then AuNPs were deposited on the surface by electro-deposition method. Morphological feature of the developed sensor was investigated by scanning electron microscope. The parameters effecting the experimental conditions such as adsorption time of graphene oxide, deposition time of gold nanoparticles, supporting electrolyte pH, pre-concentrating potential/time were optimized. Under optimum experimental conditions, good linearity was obtained for CFX response in the range between 0.02-2.0 μM of CFX concentrations with a low detection limit 0.442 nM by stripping voltammetry. The AuNPs/GO modified PGE was implemented to pharmaceutical samples with good recovery values. This study results proved that developed disposable sensor is a good alternative for the practical application of CFX analysis.

In this study, we present multiplexed anodic stripping voltammetry (ASV) detection of heavy metal ions (HMIs)—As(III), Cd(II), and Pb(II)—using a homemade electrochemical cell consisting of dual working, reference and counter screen-printed electrodes (SPE) on polyimide substrate integrated with a 3D-printed flow cell. Working and counter electrodes were fabricated by the screen-printing of graphite paste while the Ag/AgCl paste was screen-printed as a reference electrode (Ag/AgCl quasi-reference electrode). The working electrodes were modified with (BiO)2CO3-reduced graphene oxide (rGO)-Nafion [(BiO)2CO3-rGO-Nafion] and Fe3O4 magnetic nanoparticles (Fe3O4MNPs) decorated Au nanoparticles (AuNPs)-ionic liquid (IL) (Fe3O4-Au-IL) nanocomposites separately to enhance HMIs sensing. Electrochemical detection was achieved using square wave ASV technique. The desired structure of the flow electrochemical cell was optimized by the computational fluid dynamic (CFD). Different experimental parameters for stripping analysis of HMIs were optimized including deposition time, deposition potential and flow rate. The linear range of calibration curves with the sensing nanocomposites modified SPE for the three metal ions was from 0–50 μg/L. The limits of detection (S/N = 3) were estimated to be 2.4 μg/L for As(III), 1.2 μg/L for Pb(II) and 0.8 μg/L for Cd(II). Furthermore, the homemade flow anodic stripping sensor platform was used to detect HMIs in simulated river water with a 95–101% recovery, indicating high selectivity and accuracy and great potential for applicability even in complex matrices.

Herein, a sensor platform, Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE), is presented for the detection of Cd2+ and Pb2+ using square wave anodic stripping voltammetry (SWASV). The sensor was obtained through electrografting of the GCE using 4-carboxybenzene diazonium tetrafluoroborate (4-CBD) and in situ electrodeposition of Bi3+. The stability of the grafted layer and the proposed mechanism of interaction between the metal ions and the grafted layer is supported by DFT calculations. Under the optimized conditions, Pb2+ had a linear working range of 25–500 μg L−1 with LOD of 10 μg L−1 (S/N = 3) and Cd2+ provided linear range of 50–500 μg L−1 and LOD of 25 μg L−1. The fabricated electrode presented good repeatability and reproducibility. The applicability of the electrode was tested for determination of Cd2+ and Pb2+ in tap water resulting in recoveries of 96.2–101% for Cd2+ and 98.1–104% for Pb2+.

This study presents a simple, low-cost, sensitive and environmentally friendly approach for the simultaneous electrochemical determination of lead and cadmium based on a commercial screen-printed gold electrode (SPGE) with Nafion and an in situ bismuth film. The developed sensor was coated with a Nafion polymer to reduce the interference and enhance the stability and reproducibility of the gold working electrode and an in situ bismuth film to increase the sensitivity and achieve a low detection limit. Electrochemical properties were investigated using anodic stripping square voltammetry. The composite film was characterized using cyclic voltammetry, and scanning electron microscopy was carried out for the morphological characterization of the modified electrode. It was found that the prepared electrode has high sensitivity and good repeatability with a limit of detection below the Environmental Protection Agency limits (5 µg/L Cd and 10 µg/L Pb). The linear calibration curves for Pb(II) ranged from 20 ppb to 300 ppb, and for Cd(II), they ranged from 50 ppb to 300 ppb. The detection limits (S/N = 3) were estimated to be 3 ppb for Pb(II) and 4 ppb for Cd(II). This method was effectively applied in the application of river and tap water samples, and the results were compared with flame-atomic absorption spectroscopy analysis.

A method for rapid on-site determination of cadmium in crayfish by dilute acid extraction and anodic stripping voltammetry (ASV) was established. It was determined to use 3% hydrochloric acid as the extraction solution, 20 min as extraction time, 10% sodium diacetate as the basic solution in performing the anodic stripping voltammetry analysis. In the interval of (0.005–1.0) mg kg−1, the content of cadmium in crayfish had a good linear relationship with the peak current. The method was applied to the crayfish reference material. The limit of detection was 0.005 mg kg−1. The repeatability was 3.8%. The results had no significant difference between ASV and ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) method with T-test statistical method. This method is simple, rapid and sensitive. It has been carried on-site to detect real crawfish sample in food rapid detection vehicle.

An easy-to-make new working electrode, an ex-in-situ AuF/GCE, was developed for trace As(III) detection. A gold film electrode prepared ex-situ was re-plated in-situ during each arsenic deposition step by adding Au(III) into the analyte solution. The factors affecting arsenic stripping response, namely, gold film preparation conditions, electrolyte concentration, electrode cleaning potential, cleaning time, deposition potential, and deposition time, were investigated. Compared with the traditional gold film electrodes prepared ex-situ, the new electrode has better precision and linearity of arsenic differential pulse anodic stripping voltammetry responses. For a deposition time of 90 s at –200 mV, the new electrode exhibits a sensitivity, a limit of detection (3-Sigma), a limit of quantitation of 0.103 μA·L·μg–1, 0.4 μg·L–1, and 1.3 μg·L–1, respectively.

Nowadays people are becoming poisoned through the consumption of herbal remedies that comprise heavy metals (HMs) worldwide. It is possible for HMs to be present in pharmaceutical herb materials coming from anthropogenic activities like agriculture, industrial waste, and natural sources. In various ethnic groups, there is evidence that contaminants were purposefully added in the belief that they had some sort of therapeutic benefit. HM toxicity of medicinal plant products has been linked to a wide range of adverse health effects, causing dysfunction of the liver, kidney, and heart, and even death. Natural plant-based products established around the world have progressed to the point that they now combine a variety of synthetic products for their purported medical benefits. This assessment focuses on the impacts of HMs on plants, sources of HMs, herbal sample collection, and identification techniques, especially in medicinal plant samples. At the same time, it focuses on the sociocultural applications of HMs as well as the dangers associated with their usage in conventional therapies. It is necessary to implement appropriate regulation and monitoring systems for natural supplements due to the prevalence of hazardous HMs.

Monitoring of ions in real-time directly in cell culture systems and in organ-on-a-chip platforms represents a significant investigation tool to understand ion regulation and distribution in the body and ions’ involvement in biological mechanisms and specific pathologies. Innovative flexible sensors coupling electrochemical stripping analysis (square wave anodic stripping voltammetry, SWASV) with an ion selective membrane (ISM) were developed and integrated in Transwell™ cell culture systems to investigate the transport of zinc and copper ions across a human intestinal Caco-2 cell monolayer. The fabricated ion-selective sensors demonstrated good sensitivity (1 × 10−11 M ion concentration) and low detection limits, consistent with pathophysiological cellular concentration ranges. A non-invasive electrochemical impedance spectroscopy (EIS) analysis, in situ, across a selected spectrum of frequencies (10–105 Hz), and an equivalent circuit fitting were employed to obtain useful electrical parameters for cellular barrier integrity monitoring. Transepithelial electrical resistance (TEER) data and immunofluorescent images were used to validate the intestinal epithelial integrity and the permeability enhancer effect of ethylene glycol-bis(2-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA) treatment. The proposed devices represent a real prospective tool for monitoring cellular and molecular events and for studies on gut metabolism/permeability. They will enable a rapid integration of these sensors into gut-on-chip systems.