Electroanalysis最新文献

The detection of heavy metals is necessary due to their toxic characteristics and bioaccumulation potential, which can be harmful to living organisms. Chemically modified electrodes have been widely used as an alternative in the detection of heavy metal ions, aiming for improved selectivity resulting from specific interactions with these analytes. Therefore, ligands derived from bistriazolic compounds emerge as new materials capable of interacting with metallic ions, potentially enhancing the detectability of the electrode. In this context, this work aims to obtain an electrochemical sensor based on a modifier derived from bistriazoles for the determination of lead(II) ions in different samples. The 1,3-bis(4-ethyl-1H−1,2,3-triazol-1-yl)propan-2-one (BT) was characterized using spectroscopic, spectrometric, and electrochemical techniques. Additionally, a method for the determination of lead(II) ions was developed using differential pulse voltammetry (DPV), where the bis-triazole modified electrode demonstrated remarkable detectability for Pb²⁺. Optimizations of the scan medium and DPV technique parameters showed a significant increase in the analytical signal current for Pb²⁺. An analytical curve was obtained, and the developed method achieved a limit of detection of 0.10 nmol L⁻¹. The method was applied to quantify the analyte in tap water, river water, and firearm discharge residue samples with recovery values ranging from 87.8% to 118%, highlighting the reliability and precision of the developed method.

Palladium nanoparticles supported on a pretreated carbon substrate (Pd/C) were synthesized from a surfactant-free microwave-heated ethylene glycol without any external reducing agent and characterized by high-resolution electron transmission microscopy, thermogravimetric analysis, and X-ray diffraction analysis. Cyclic voltammetry was effectively employed to scrutinize the electrochemical processes such as Pd hydrogen interactions including hydrogen adsorption, absorption, desorption, and hydrogen evolution as well as Pd–oxygen interactions like the oxide formation and the subsequent reduction of the oxide layer. The electrochemical oxidation of palladium was clearly indicated at the potential ranging from 0.78 to 1.20 V versus reversible hydrogen electrode (RHE) in the anodic scan direction whereas the corresponding reduction peak was observed with a broad peak centered at 0.79 V versus RHE in the reverse scan. Therefore, an accurate evaluation of the EASA measurements on ultrathin film palladium (Pd/C) electrodes in acidic (0.5 mol L⁻¹ H₂SO₄, pH ∼ 1) media was successfully conducted. Moreover, the steady-state cyclic voltammetry (CV) measurements have been conducted at the lowest scan rate of 1 mV s⁻¹, enabling obtaining of hydrogen adsorption, absorption, and desorption reaction features without concurrent. Besides, Pd/C electrocatalyst exhibited 129 mV overpotential yielding a cathodic current density of 10 mA cm⁻² toward hydrogen evolution reaction. This study outlines the description of practical experimental conditions essential for accurately determining the EASA that facilitates a comprehensive evaluation of their electrochemical performance.

The detection of heavy metals is necessary due to their toxic characteristics and bioaccumulation potential, which can be harmful to living organisms. Chemically modified electrodes have been widely used as an alternative in the detection of heavy metal ions, aiming for improved selectivity resulting from specific interactions with these analytes. Therefore, ligands derived from bistriazolic compounds emerge as new materials capable of interacting with metallic ions, potentially enhancing the detectability of the electrode. In this context, this work aims to obtain an electrochemical sensor based on a modifier derived from bistriazoles for the determination of lead(II) ions in different samples. The 1,3-bis(4-ethyl-1H−1,2,3-triazol-1-yl)propan-2-one (BT) was characterized using spectroscopic, spectrometric, and electrochemical techniques. Additionally, a method for the determination of lead(II) ions was developed using differential pulse voltammetry (DPV), where the bis-triazole modified electrode demonstrated remarkable detectability for Pb²⁺. Optimizations of the scan medium and DPV technique parameters showed a significant increase in the analytical signal current for Pb²⁺. An analytical curve was obtained, and the developed method achieved a limit of detection of 0.10 nmol L⁻¹. The method was applied to quantify the analyte in tap water, river water, and firearm discharge residue samples with recovery values ranging from 87.8% to 118%, highlighting the reliability and precision of the developed method.

Palladium nanoparticles supported on a pretreated carbon substrate (Pd/C) were synthesized from a surfactant-free microwave-heated ethylene glycol without any external reducing agent and characterized by high-resolution electron transmission microscopy, thermogravimetric analysis, and X-ray diffraction analysis. Cyclic voltammetry was effectively employed to scrutinize the electrochemical processes such as Pd hydrogen interactions including hydrogen adsorption, absorption, desorption, and hydrogen evolution as well as Pd–oxygen interactions like the oxide formation and the subsequent reduction of the oxide layer. The electrochemical oxidation of palladium was clearly indicated at the potential ranging from 0.78 to 1.20 V versus reversible hydrogen electrode (RHE) in the anodic scan direction whereas the corresponding reduction peak was observed with a broad peak centered at 0.79 V versus RHE in the reverse scan. Therefore, an accurate evaluation of the EASA measurements on ultrathin film palladium (Pd/C) electrodes in acidic (0.5 mol L⁻¹ H₂SO₄, pH ∼ 1) media was successfully conducted. Moreover, the steady-state cyclic voltammetry (CV) measurements have been conducted at the lowest scan rate of 1 mV s⁻¹, enabling obtaining of hydrogen adsorption, absorption, and desorption reaction features without concurrent. Besides, Pd/C electrocatalyst exhibited 129 mV overpotential yielding a cathodic current density of 10 mA cm⁻² toward hydrogen evolution reaction. This study outlines the description of practical experimental conditions essential for accurately determining the EASA that facilitates a comprehensive evaluation of their electrochemical performance.

Tryptophan (TRP) in the human body is generally metabolized by two different pathways, to serotonin or via kynurenine (KYN), where the majority is consumed through the latter. Studies relate that the imbalance between these two pathways is associated with different types of diseases. This work aims to investigate for the first time the redox properties of KYN in aqueous electrolytes on glassy carbon electrode (GCE), using electrochemical techniques, cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). The electrooxidation of KYN was compared with the anodic behavior of aniline and kynurenic acid. The KYN oxidation mechanism was proposed and occurs in the 2-aminobenzoyl group from a main step with the withdrawal of one electron and the formation of an intermediate cation radical (KYN^+•). The KYN^+• follows a dimerization and polymerization reaction, forming different electroactive products (polyKYNs) that are adsorbed on the GCE surface. The EIS data indicated that the adsorbed polyKYNs films on GCEs in a strongly acidic medium (pH = 0.3) are conductive and in a physiological medium they are resistive, hindering new subsequent reactions. All redox reactions identified were dependent on an acid–base equilibrium, since they were strongly influenced by the pH of the medium, occurring more easily in alkaline media. The diffusion coefficient of KYN was determined in phosphate buffer pH = 7.0 as 1.59 × 10⁻⁶ cm² s⁻¹. The voltammetric responses of DP were also explored here for the development of a sensitive electroanalytical method for detection and quantification of KYN. For the development of the method, analytical parameters were studied, such as work concentration range, linearity, limit of detection (LOD) and quantification (LOQ), repeatability, reproducibility, and selectivity to possible interferences. A method using DPV and GCE was developed for determination of KYN in acidic medium (pH = 0.30) with a LOD of 0.43 μmol L⁻¹.

Tryptophan (TRP) in the human body is generally metabolized by two different pathways, to serotonin or via kynurenine (KYN), where the majority is consumed through the latter. Studies relate that the imbalance between these two pathways is associated with different types of diseases. This work aims to investigate for the first time the redox properties of KYN in aqueous electrolytes on glassy carbon electrode (GCE), using electrochemical techniques, cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). The electrooxidation of KYN was compared with the anodic behavior of aniline and kynurenic acid. The KYN oxidation mechanism was proposed and occurs in the 2-aminobenzoyl group from a main step with the withdrawal of one electron and the formation of an intermediate cation radical (KYN^+•). The KYN^+• follows a dimerization and polymerization reaction, forming different electroactive products (polyKYNs) that are adsorbed on the GCE surface. The EIS data indicated that the adsorbed polyKYNs films on GCEs in a strongly acidic medium (pH = 0.3) are conductive and in a physiological medium they are resistive, hindering new subsequent reactions. All redox reactions identified were dependent on an acid–base equilibrium, since they were strongly influenced by the pH of the medium, occurring more easily in alkaline media. The diffusion coefficient of KYN was determined in phosphate buffer pH = 7.0 as 1.59 × 10⁻⁶ cm² s⁻¹. The voltammetric responses of DP were also explored here for the development of a sensitive electroanalytical method for detection and quantification of KYN. For the development of the method, analytical parameters were studied, such as work concentration range, linearity, limit of detection (LOD) and quantification (LOQ), repeatability, reproducibility, and selectivity to possible interferences. A method using DPV and GCE was developed for determination of KYN in acidic medium (pH = 0.30) with a LOD of 0.43 μmol L⁻¹.

Tantalum (Ta) nanoparticles were synthesized by the reaction of lithium with pyridine solution of TaCl₅ via ultrasonication. Then, Ta nanoparticles and graphene nanoplatelets (GNP) were utilized to construct a novel sensing platform for the voltammetric detection of ritodrine. The electrochemically active surface area and charge transfer resistance (R_ct) of the proposed electrochemical platform (GCE/GNP@Ta) were determined to be 0.336 cm² and 86 Ω. This indicates that proposed material can be considered as a promising material in sensing applications. The performance of GCE/GNP@Ta was examined for ritodrine oxidation process and compared with other electrodes. GCE/GNP@Ta improved the voltammetric behavior of ritodrine and exhibited an oxidation peak potential (E_p) of 0.71 V, which is less than that of other electrodes. The potential shift and peak improvement of ritodrine indicated the higher electrocatalytic activity of electrode modified with GNP@Ta. GCE/GNP@Ta exhibited a working range from 4.0 × 10⁻⁸ to 1.5 × 10⁻⁶ M with a detection limit of 1.0 × 10⁻⁹ M (3s_b/m) for ritodrine. The voltammetric measurements yielded excellent accuracy and high precision for ritodrine in biological samples.

Tantalum (Ta) nanoparticles were synthesized by the reaction of lithium with pyridine solution of TaCl₅ via ultrasonication. Then, Ta nanoparticles and graphene nanoplatelets (GNP) were utilized to construct a novel sensing platform for the voltammetric detection of ritodrine. The electrochemically active surface area and charge transfer resistance (R_ct) of the proposed electrochemical platform (GCE/GNP@Ta) were determined to be 0.336 cm² and 86 Ω. This indicates that proposed material can be considered as a promising material in sensing applications. The performance of GCE/GNP@Ta was examined for ritodrine oxidation process and compared with other electrodes. GCE/GNP@Ta improved the voltammetric behavior of ritodrine and exhibited an oxidation peak potential (E_p) of 0.71 V, which is less than that of other electrodes. The potential shift and peak improvement of ritodrine indicated the higher electrocatalytic activity of electrode modified with GNP@Ta. GCE/GNP@Ta exhibited a working range from 4.0 × 10⁻⁸ to 1.5 × 10⁻⁶ M with a detection limit of 1.0 × 10⁻⁹ M (3s_b/m) for ritodrine. The voltammetric measurements yielded excellent accuracy and high precision for ritodrine in biological samples.

The development of new sensors for dopamine (DP) detection is crucial due to its role as one of the most important neurotransmitters for maintaining mental health. In this context, a novel and simple 2D screen-printed carbon electrode (SPCE) molecularly modified electrode with a methylphenidate film was developed. This electrode exhibited notable activity in DP oxidation at potential values below 0.3 V, achieving a 300% increase in anodic current compared to the unmodified SPCE in an acidic environment (pH 3.0) with phosphate buffer solution. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrode's electrochemical behavior. The electrode achieved a DP detection limit of 0.15 µmol/L using linear scan voltammetry. Interference studies with ascorbic acid and uric acid confirmed the electrode's selectivity for DP detection. The sensor's effectiveness was validated using real human urine samples, demonstrating accurate and reliable performance.

Bisphenol A (BPA) exposure poses significant health risks, making its analysis essential. This study presents a portable electrochemical sensing platform using copper nanoparticles (CuNPs) decorated on a laser-induced graphene (LIG) electrode (CuNPs@LIGE). The platform is created through a one-step laser-induced synthesis that combines polyimide and metal precursors, resulting in a three-dimensional porous structure. The sensor utilizes linear scan voltammetry for BPA detection with a smartphone-connected electrochemical workstation. The presence of CuNPs in LIG enhances electrical conductivity and response signals. Under optimal conditions, the sensor achieves a detection range from 0.1 μmol/L to 10.0 mmol/L and a low detection limit of 0.033 μmol/L (3σ), demonstrating good stability and selectivity. Additionally, it shows recovery rates between 95.71% and 99.17% for BPA detection in seawater samples, making it a strong candidate for rapid BPA monitoring applications.