Preparation of Cu (II) imprinted polymer electrode and its application for potentiometric and voltammetric determination of Cu (II)

The Cu (II) imprinted polymer glassy carbon electrode (GCE/Cu-IP) was prepared by electropolymerization of pyrrole at GCE in the presence of methyl red as a dopant and then imprinting by Cu²⁺ ions. This electrode was applied for potentiometric and voltammetric detection of Cu²⁺ ion. The potentiometric response of the electrode was linear within the Cu²⁺ concentration range of 3.9 × 10^?6 to 5.0 × 10^?2 M with a near-Nernstian slope of 29.0 mV decade^?1 and a detection limit of 5.0 × 10^?7 M. The electrode was also used for preconcentration anodic stripping voltammetry and results exhibited that peak currents for the incorporated copper species were dependent on the metal ion concentration in the range of 1.0 × 10^?8 to 1.0 × 10^?3 M and detection limit was 6.5 × 10^?9 M. Also the selectivity of the prepared electrode was investigated. The imprinted polymer electrode was used for the successful assay of copper in two standard reference material samples.     

MCM/ZrO2 nanoparticles modified electrode for simultaneous and selective voltammetric determination of epinephrine and acetaminophen

A novel MCM/ZrO₂ nanoparticles modified carbon paste electrode (MZ-CPE) was fabricated and used to study the electro oxidation of epinephrine (EP) and acetaminophen (AC) and their mixtures by electrochemical methods. The modified electrode showed electrocatalytic activity toward EP and AC oxidation with a decrease of the overpotential by 173 mV to a less positive potential for EP at the surface of the MZ-CPE and an increase in peak current at pH 7.0. Differential pulse voltammetry peak currents of EP and AC increased linearly with their concentrations in the ranges of 1.0 × 10^?6–2.5 × 10^?3 and 1.0 × 10^?6–2.0 × 10^?3 M, respectively, and the detection limits for EP and AC were 5.0 × 10^?7 and 4.5 × 10^?7 M, respectively.     

Application of 2-(3,4-dihydroxyphenyl)-1,3-dithialone self-assembled monolayer on gold electrode as a nanosensor for electrocatalytic determination of dopamine and uric acid

The electrooxidation of dopamine (DA), uric acid (UA) and their mixture on a gold electrode modified by a self-assembled monolayer of 2-(3,4-dihydroxyphenyl)-1,3-dithialone has been studied by cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). CV was used to investigate the redox properties of the modified electrode at various scan rates and the apparent charge transfer rate constant (k(s)), and transfer coefficient (α) were calculated. The mediated oxidation of DA at the modified electrode under the optimum condition (pH = 7.0) in CV occurs at a potential about 220 mV less positive than that of the unmodified gold electrode. The values of electron transfer coefficients (α), catalytic rate constant (k) and diffusion coefficient (D) were calculated for DA, using electrochemical methods. DPV exhibited a linear dynamic range over the concentration range of 0.2-250.0 μM and a detection limit (3σ) of 0.07 μM for DA. The modified electrode was used for simultaneous determination of DA and UA by DPV. The results showed that the electrode is highly efficient for the catalytic electrooxidation of DA and UA, leading to a remarkable peak resolution (~350 mV) for two compounds. The electrode was used for the determination of DA in an injection sample.     

Electro-assisted self-assembly of mesoporous silica thin films: application to electrochemical sensing of glutathione in the presence of copper

Journal of Solid State Electrochemistry - Oxidation of the reduced form of glutathione based on the 1:1 copper(Cu+2)-glutathione(GSH) complexes was found to occur at a decreased overpotential at a...     

Electrochemical behavior of electrodeposited rutin film on a multi-wall carbon nanotubes modified glassy carbon electrode. Improvement of the electrochemical reversibility and its application as a hydrazine sensor

By immobilizing rutin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWCNT), a new modified electrode has been fabricated and its electrochemical behavior was investigated by cyclic voltammetry. Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple with surface confined characteristics. The results show that the reversibility of rutin is significantly improved at a MWCNT modified GCE in comparison with GCE alone. The charge transfer coefficient, α, was calculated to be 0.4, and charge transfer rate constant, k_s, was 46.7 s⁻¹ in pH 8, indicating great facilitation of the electron transfer between rutin and MWCNT deposited on the electrode surface. The rutin MWCNT (RMWCNT) modified GCE showed excellent mediation of hydrazine oxidation: a decrease in the overvoltage of hydrazine electrooxidation was observed as well as a dramatic increase in the peak current compared to that seen at a rutin modified GCE (RMGCE), activated GCE or bare GCE. Hydrazine was determined amperometrically at the surface of RMWCNT modified GCE in pH 8. Under the optimized conditions the calibration curve is linear in the concentration range 2.0–190.0 μM hydrazine. The detection limit and sensitivity are 0.61 μM and 0.0656 μA μM⁻¹, respectively. Finally the kinetic parameters of the electron transfer coefficient, α, the heterogeneous rate constant of dependent to different potentials, k′(E), and the standard heterogeneous rate constant, k⁰, for oxidation of hydrazine at the RMWCNT surface were determined using various electrochemical methods. The advantages of this modified electrode for hydrazine determination are high sensitivity, excellent catalytic activity, short response time, wide linear range, and high exchange current density.     

Homogeneous and nanomolar detection of hydrazine by indigocarmine as a mediator at the surface of TiO2 nanoparticles modified carbon paste electrode

The homogeneous electrocatalytic oxidation of hydrazine（HZ） has been studied by indigocarmine（IND） as a mediator at the surface of TiO₂ nanoparticles modified carbon paste electrode（TNMCPE）.Cyclic voltammetry was used to study the electrochemical behavior of IND at different scan rates.The voltammetric response of the modified electrode was linear against the concentration of HZ in the ranges of 3.0×l0^-8-7.0×10⁶ mol/L with differential pulse voltammetry method.The detection limit（3σ） was determined as 27.3 nmol/L.To evaluate the applicability of the proposed method to real samples,the modified CPE was applied to the determination of HZ in water samples.     

Graphene sheet for improving the electrocatalytic activity of a benzofuran derivative modified electrode for determination of epinephrine in the presence of serotonin

A nanocomposite system based on coumarin derivative and graphene sheet was used to prepare a new electrochemical sensor. The objective of the mentioned nanocomposite was to investigate novel electrochemical properties enabling the quantification of epinephrine (Ep). Cyclic voltammetry was used to study the redox properties of the mentioned modified electrode at different scan rates. Henceforward, the electrocatalytic oxidation of Ep at the surface of the modified electrode was considered. The data has shown excellent catalytic activity of the modified electrode for the electrooxidation of Ep, which leads to a reduction of overpotential for more than 238 mV. According to differential pulse voltammetry (DPV), the oxidation of Ep showed a dynamic range between 0.1 and 1000.0 μM and the detection limit (3s) of 0.011 μM. Besides, DPV was used for the determination of Ep at the mentioned modified electrode in the presence of serotonin.     

High-performance electrochemical sensor based on electrodeposited iron oxide nanoparticle: catecholamine as analytical probe

In this paper, we report the synthesis and electrocatalytic activity of electrodeposited Fe₂O₃ nanoparticles modified on a glassy carbon electrode as highly sensitive sensors for determination of catecholamines. Results showed that the Fe₂O₃ nanoparticles on a glassy carbon electrode exhibit excellent catalytic activity toward catecholamines oxidation, including levodopa, dopamine, and epinephrine, resulting in a marked lowering in the peak potential and considerable improvement of the peak current as compared to the electrochemical activity at the bare glassy carbon electrode. The electrochemical characterizations of catecholamines were performed using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry techniques. The electrocatalytic currents increase linearly with the levodopa, dopamine, and epinephrine concentrations in the ranges of 0.0625–1000, 0.25–1500, and 0.125–1000 µM, respectively, and the detection limits (3σ) were 24 ± 2, 14 ± 2, and 12 ± 2 nM, respectively.     

Solid phase extraction of trace amounts of silver (I) using dithizone-immobilized alumina-coated magnetite nanoparticles prior to determination by flame atomic absorption spectrometry

A new, simple, fast and reliable solid-phase extraction (SPE) method has been developed to separation/preconcentration of trace amounts of silver ion from environmental water samples using dithizone/sodium dodecyl sulfate immobilized on alumina-coated magnetite nanoparticles (DTZ/SDS-ACMNPs) and its determination by flame atomic absorption spectrometry. The coating of alumina on Fe₃O₄ NPs not only avoids the dissolving of Fe₃O₄ NPs in acidic solution, but also extends their application without sacrificing their unique magnetization characteristics. This method avoided the time-consuming column-passing process of loading large volume samples in traditional SPE through the rapid isolation of DTZ/SDS-ACMNPs with an adscititious magnet. Optimal experimental conditions including amount of DTZ/SDS, pH value, standing time, sample volume, type, volume and concentration of eluent and co-existing ions have been studied and established. Under the optimal experimental conditions, the detection limit for Ag(I) with enrichment factors of 100 was found to be 0.52?ng?mL^?1 and its relative standard deviations (RSD) was 3.4% (n?=?10, C?=?5.0?µg?mL^?1). The linear range of calibration curve for Ag(I) was 2–5000?ng?mL^?1 with a correlation coefficient of 0.9991. The proposed method was successfully applied to the determination of target analyte in different water and wastewater samples. The validity of the method has been checked by applying it to study the recovery of silver ion in spiked water and wastewater samples.