Search Results (290)

Herein, we propose an ultrasensitive electrochemical immunosensor based on glucose oxidase labeling and enzyme-catalyzed Au staining. In brief, the primary antibody (Ab₁), bovine serum albumin, an antigen and then a bionanocomposite that contains a second antibody (Ab₂), poly(3-anilineboronic acid) (PABA), Au nanoparticles (AuNPs) and glucose oxidase (GOx) are modified on a glassy carbon electrode coated with multiwalled carbon nanotubes, yielding a corresponding sandwich-type immunoelectrode. In the presence of glucose, a chemical reduction of NaAuCl₄ by enzymatically generated H₂O₂ can precipitate a lot of gold on the Ab₂-PABA-AuNPs-GOx immobilized immunoelectrode. In situ anodic stripping voltammetry (ASV) detection of gold in 8 μL 1.0 M aqueous HBr-Br₂ is conducted for the antigen assay, and the ASV detection process takes approximately 6 min. This method is employed for the assay of human immunoglobulin G (IgG) and human carbohydrate antigen 125 (CA125), which demonstrates exceptional sensitivity, high selectivity and fewer required reagents/samples. The achieved limits of detection (S/N = 3) by the method are 0.25 fg mL⁻¹ for IgG (approximately equivalent to containing 1 IgG molecule in the 1 microlitre of the analytical solution) and 0.1 nU mL⁻¹ for CA125, which outperforms many previously reported results. Full article

Thallium is a soft metal with a grey or silvery hue. It commonly occurs in two oxidation states in chemical compounds: Tl⁺ and Tl³⁺. Thermodynamically, Tl⁺ is significantly more stable and typically represents the dominant form of thallium in environmental systems. However, in this chemical form, thallium remains highly toxic. This study focuses on the modification of a glassy carbon electrode (GCE) with silver nanostructures stabilised by potato starch derivatives. The modified electrode (GCE/AgNPs-E1451) was used for the determination of trace amounts of thallium ions using anodic stripping voltammetry. Emphasis was placed on assessing the effect of surface modification on key electrochemical performance parameters of the electrode. Measurements were carried out in a base electrolyte (EDTA) and in a real soil sample collected from Bali. The stripping peak current of thallium exhibited linearity over the concentration range from 19 to 410 ppb (9.31 × 10⁻⁸ to 2.009 × 10⁻⁶ mol/dm³). The calculated limit of detection (LOD) was 18.8 ppb (9.21 × 10⁻⁸ mol/dm³), while the limit of quantification (LOQ), corresponded to 56.4 ppb (2.76 × 10⁻⁷ mol/dm³). The GCE/AgNPs-E1451 electrode demonstrates several significant advantages, including a wide detection range, reduced analysis time due to the elimination of time-consuming pre-concentration steps, and non-toxic operation compared to mercury-based electrodes. Full article

Due to its conjugated structure, 1,4,6,8-tetrakis((E)-2-(thiophen-2-yl)vinyl)azulene (L) has a high potential for nonlinear optics and coloring. This compound was studied electrochemically using cyclic voltammetry, pulse differential voltammetry and rotating disk voltammetry in organic electrolytes. The main processes occurring during oxidation and reduction scans were highlighted and characterized. Density functional theory (DFT) calculations were conducted to assess the chemical reactivity of this compound. UV-Vis studies of L were performed in acetonitrile to establish the optical parameters in this solvent and its complexing power towards heavy metal (HM) ions. Chemically modified electrodes (CMEs) based on L were prepared by electrooxidation of L in organic electrolytes. To evaluate the electrochemical behavior of the CMEs, they were characterized with a ferrocene redox probe. They were also tested for the analysis of synthetic samples of heavy metal ions (HM): Cd(II), Pb(II), Cu(II) and Hg(II) by anodic stripping. Specific responses were obtained for Pb(II) and Cd(II) ions. The preparation conditions have an influence on the electrochemical responses. This study is relevant for the design and further development of advanced materials based on this azulene for the analysis of HMs in water samples. Electrochemical experiments and DFT calculations recommended L as a new ligand for modifying the electrode surface for the analysis of HMs. Full article

Xylazine (XYL), an FDA-approved veterinary tranquilizer, is being abused both as an opioid adulterant in a street-drug known as “Tranq-dope” and as a date rape drug. Given its now nearly ubiquitous use with fentanyl and fentanyl derivatives across the globe, XYL has become a primary target for researchers seeking to develop portable and cost-effective sensors for its detection. Electrochemical sensors based on the oxidation of XYL, while useful, have limitations due to certain interferents and inherent electrode fouling that render the approach less reliable, especially in certain sample matrices. In this work, modified electrode platforms incorporating layers of multi-walled carbon nanotubes for sensitivity along with semi-permeable polyurethane (PU) layers and host–guest chemistry using β-cyclodextrin for selectivity are deployed for XYL detection using complementary adsorptive cathodic stripping analysis. The modified electrode sensors are optimized to minimize high potentials and maintain fouling resistant capabilities and investigated to better understand the function of the PU layer. The use of adsorptive cathodic stripping differential pulse voltammetry indirectly indicates the presence and concentration of XYL within complex sample media (beverages and synthetic urine). When used in this manner, the modified electrodes exhibited an overall average sensitivity of ~35 (±9) nA/μM toward XYL with a limit of quantification of <10 ppm, while also offering adaptability for the analysis of XYL in different types of samples. By expanding the capability of these XYL sensors, this study represents another facet of tool development for use by medical professionals, first-responders, forensic investigators, and drug-users to limit exposure and help stem the dangerous and illegal use of XYL. Full article

Electrochemical sensors have been developed based on polyethylene terephthalate track-etched membranes (PET TeMs) modified by photograft copolymerization of N-vinylformamide (N-VFA) and trimethylolpropane trimethacrylate (TMPTMA). The modification, structure and properties of the modified PET TeMs were thoroughly characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, gas permeability measurements and contact angle analysis. Optimal membrane modification was achieved using C = 10% (N-VFA), 60 min of UV irradiation and a UV lamp distance of 10 cm. Furthermore, the modified membranes were implemented in a two-electrode configuration for the determination of Eu³⁺, Gd³⁺, La³⁺ and Ce³⁺ ions via square-wave anodic stripping voltammetry (SW-ASV). The sensors exhibited a linear detection range from 10⁻⁷ M to 10⁻³ M, with limits of detection of 1.0 × 10⁻⁶ M (Eu³⁺), 6.0 × 10⁻⁶ M (Gd³⁺), 2.0 × 10⁻⁴ M (La³⁺) and 2.5 × 10⁻⁵ M (Ce³⁺). The results demonstrated a significant enhancement in electrochemical response due to the grafted PET TeMs-g-N-PVFA-TMPTMA structure, and the sensor showed practical applicability and consistent performance in detecting rare earth ions in tap water. Full article

In this work, we designed a novel and simple electrochemical approach for the determination of daidzein antioxidant (Dz) in peanut oil samples. The Dz determination was based on anodic stripping linear voltammetry using screen-printed graphene electrodes (SPGEs) activated in acidic media, where a strong adsorption of Dz on activated graphene was obtained. In this regard, electroanalytical parameters such as the scan rate, supporting electrolyte, pH, and accumulation step were optimized to ensure the best conditions for the selective and sensitive Dz quantification. The electrochemical method developed for the determination of Dz exhibits a linear behavior of the anodic peak current in the concentration range from 0.05 to 1 μM, with a limit of detection of 0.012 μM. The electrochemical sensor demonstrated to the capacity to quantify Dz in peanut oil samples at low concentrations without the necessity of an extensive sample pretreatment. Therefore, the electrochemical method proposed can be used as a new portable analytical tool for the in situ quality control of peanut oil samples. Full article

An advanced anodic stripping voltammetry (ASV)-based Micro Electro Mechanical System (MEMS) sensor for cadmium (Cd) detection is presented in this study, which is cost-effective and efficient for in situ water monitoring, providing a crucial early warning mechanism, streamlining environmental monitoring, and facilitating timely intervention to safeguard public health and environmental safety. The rationale behind this work is to address the critical need for an in situ monitoring system for cadmium (Cd) in freshwater sources, particularly those adjacent to agricultural fields. Cd(II) is a highly toxic heavy metal that poses a significant threat to agricultural ecosystems and human health due to its rapid bioaccumulation in plants and subsequent entry into the food chain. The developed analytic device is composed of a commercial mercury salt-modified graphite screen-printed electrode (SPE) with a custom-designed innovative polydimethylsiloxane (PDMS) flow detection cell. The flow cell was prototyped using 3D printing and replica moulding, with its design and performance validated through COMSOL Multiphysics simulations to optimize inflow conditions and ensure maximum analyte dispersion on the working electrode surface. Chemical detection was performed using square wave voltammetry, demonstrating a linear response for Cd(II) concentrations of 0 to 20 µg/L. The system exhibited robust analytical performance, enabling 25–30 daily analyses with consistent sensitivity within the Limit of Detection (LoD) set by the law of 3 µg/L. Full article

A new type of solid bismuth microelectrode array characterized by eco-friendly properties and the simplicity of its construction is presented for the first time. The proposed array of microelectrodes consists of exactly forty-three single capillaries of an inner diameter of about 10 µm filled with metallic bismuth and packed in one casing. The proposed sensor is reusable thanks to its distinctive design. The microelectrode properties of the proposed working electrodes were confirmed by comparing the analytical signals of cadmium and lead recorded from stirred and unstirred solutions during the deposition step. The practical application of the solid bismuth microelectrode array is presented by detailing the procedure for the simultaneous determination of Pb and Cd by anodic stripping voltammetry. The calibration graphs were linear from 5 × 10⁻⁹ to 2 × 10⁻⁷ mol L⁻¹ and 2 × 10⁻⁹ to 2 × 10⁻⁷ mol L⁻¹ for Cd(II) and Pb(II), respectively (deposition time of 60 s). The detection limits for Cd(II) and Pb(II) were equal to 2.3 × 10⁻⁹ mol L⁻¹ and 8.9 × 10⁻¹⁰ mol L⁻¹, respectively. Potential interferences were investigated. The developed procedure was successfully used for the analysis of certified water reference material and environmental water samples. Full article

Lead (Pb) and cadmium (Cd) ions have serious negative impacts on human health and the ecological environment due to toxicity, persistence and nonbiodegradability. Among various trace Pb and Cd ions detection technologies, electrochemical analysis is considered as one of the most promising methods. The deposition of Bi nanoparticles on delaminated Ti₃C₂T_x (DL-Ti₃C₂T_x) develops a sensor with good conductivity and performance. Square wave anodic stripping voltammetry (SWASV) technology was applied to simultaneously deposit Bi on DL-Ti₃C₂T_x/GCE and achieve the rapid detection of Pb and Cd ions. The Bi nanoparticles effectively improved the sensitivity of Bi/DL-Ti₃C₂T_x/GCE sensors to detect Pb and Cd ions. The preparation conditions of the Bi/DL-Ti₃C₂T_x/GCE were optimized, including DL-Ti₃C₂T_x droplet amount, solution pH, Bi³⁺ concentration, deposition time and deposition potential, to improve the detection ability. The Bi/DL-Ti₃C₂T_x/GCE sensor has detection limits of 1.73 and 1.06 μg/L for Pb and Cd ions, respectively (S/N > 3). This electrochemical sensor is easy, sensitive and selective to apply in actual water samples for trace Pb and Cd ions detection. Full article

This paper proposes an environmentally friendly sensor for determining trace amounts of diclofenac (DCF)—an activated glassy carbon electrode (aGCE). Such a sensor was achieved by simple surface activation of a glassy carbon electrode to perform five cyclic voltammetric scans from −1.5 to 2.5 V at a scan rate (υ) of 100 mV/s in 0.1 M NaOH. This type of activation results in the formation of surface functional groups, which provide several advantages such as the creation of new active sites, the improvement of electron transfer dynamics, and sensor electrocatalytic activity. The electrode prepared in this way was used to develop a new differential pulse adsorptive stripping voltammetric procedure (DPAdSV) for rapid, simple, and sensitive DCF analysis. Thanks to this procedure, the following calibration curve range was obtained: 1–100 nM with low detection and quantification limits of 0.25 and 0.83 nM, respectively. To show the practical application of the method, DCF was successfully determined in commercially available pharmaceutical preparations with the standard addition method. Full article

A new voltammetric sensor (BDDE/Nafion@Fe₃O₄/BiF) was fabricated by applying a nanocomposite drop of Fe₃O₄ magnetic nanoparticles in Nafion onto the polished boron-doped diamond electrode (BDDE) surface. Then, after drying (5 min at room temperature), the electrode was electrochemically modified with bismuth film (BiF) during in situ analysis. The Nafion@Fe₃O₄/BiF modification of the BDDE contributes to the acquisition of the highest differential-pulse adsorptive stripping voltammetric (DPAdSV) signals of caffeine (CAF) due to the improvement of electron transfer and the increase in the number of active sites on which CAF can be adsorbed. The DPAdSV signals exhibited a linearly varied oxidation peak with the CAF concentration range between 0.5 and 10,000 nM, leading to the 0.043 and 0.14 nM detection and quantification limits, respectively. The practical applicability of the DPAdSV procedure using the BDDE/Nafion@Fe₃O₄/BiF was positively confirmed with commercially available energy drinks. Full article

An experimental and computational methodology was developed for ionic speciation of Pb²⁺ and Cd²⁺ with dissolved organic matter (DOM) in surface seawater (SSW) from the Bay of Bengal (BoB) in eastern Bangladesh. Differential pulse anodic stripping voltammetry (DPASV) with a thin mercury film glassy carbon electrode (TMFGC) was used to measure free and DOM-bound Pb²⁺ and Cd²⁺. A continuous binding model was used to calculate the binding constants for metal ions with experimentally found complex ligands like DOM in the BoB. The ionic speciation and distribution of all major naturally occurring ions and toxic Pb²⁺, Cd²⁺, and DOM were calculated using a computational chemical equilibrium model, MINTEQA. We found that the change in pH with increasing dissolved carbon dioxide due to global warming will cause drastic changes in the bioavailability of Pb²⁺ by the year 2050. Full article

A composite (N-rGO@ppy) of N-doped reduced graphene oxide (N-rGO) coated with polypyrrole (ppy) particles was successfully synthesized. The incorporation of N-rGO significantly mitigates the aggregation of ppy synthesized in situ, and the doped N atoms improve the conductivity of graphene oxide (GO), thereby enhancing N-rGO@ppy’s redox properties. Firstly, a glassy carbon electrode (GCE) modified with N-rGO@ppy (N-rGO@ppy/GCE) was used in combination with a bismuth film and square-wave anodic stripping voltammetry (SWASV) for the simultaneous trace analysis of Pb²⁺ and Cd²⁺. N-rGO@ppy/GCE exhibited distinct stripping peaks for Pb²⁺ and Cd²⁺, with a linear range of 1 to 500 μg L⁻¹. The limits of detection (LODs) were found to be 0.080 μg L⁻¹ for Pb²⁺ and 0.029 μg L⁻¹ for Cd²⁺, both of which are significantly below the standards set by the World Health Organization (WHO). Subsequently, the same electrochemical sensing strategy was adapted to a more portable screen-printed electrode (SPE) to accommodate the demand for in situ detection. The performance of N-rGO@ppy/SPE for analyzing Pb²⁺ and Cd²⁺ in actual samples, such as drinking water, milk, and honey, showed results consistent with those obtained from conventional graphite furnace atomic absorption spectrometry (GFAAS). Full article

Excessive levels of heavy metal pollutants in the environment pose significant threats to human health and ecosystem stability. Consequently, the accurate and rapid detection of heavy metal ions is critically important. A AgNPs@CeO₂/Nafion composite was prepared by dispersing nano-ceria (CeO₂) in a Nafion solution and incorporating silver nanoparticles (AgNPs). The morphology, microstructure, and electrochemical properties of the modified electrode materials were systematically characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and cyclic voltammetry (CV). By leveraging the oxygen vacancies and high electron transfer efficiency of CeO₂, the strong adsorption capacity of Nafion, and the superior conductivity of AgNPs, an AgNPs@CeO₂/Nafion/GCE electrochemical sensor was developed. Under optimized conditions, trace Pb²⁺ in water was detected using square wave anodic stripping voltammetry (SWASV). The sensor demonstrated a linear response for Pb²⁺ within the concentration range of 1–100 μg·L⁻¹, with a detection limit of 0.17 μg·L⁻¹ (S/N = 3). When applied to real water samples, the method achieved recovery rates between 93.7% and 110.3%, validating its reliability and practical applicability. Full article

We report the first synthesis of zwitterionic thiacalixarenes featuring imidazolium and sulfonate groups on the upper rim and alkyl (butyl or octyl) fragments on the lower rim of the platform. Despite their amphiphilic structure, these macrocycles exhibit limited water solubility. However, dynamic light scattering detected the formation of associates for derivatives with octyl moieties at a concentration of 0.1 mM. To develop stable materials for aqueous environments and to investigate the functionality of zwitterionic sulfonate-imidazolium groups along with the thiacalixarene platform, mixed organo-organic systems based on polydiacetylene polymer were created. Characterization of the modified polydiacetylene systems through various analytical methods revealed a significant colorimetric response to lead ions in aqueous media, surpassing that of the unmodified polydiacetylene polymer. Additionally, the modified polymers demonstrated efficacy in purifying aqueous media from lead ions, as evidenced by anodic stripping voltammetry (ASV) and microwave plasma atomic emission spectroscopy (MP AES). Full article