Differential Pulse Anodic Stripping Voltammetry for Mercury Determination

Introduction: Propranolol (PROP) as a nonselective β-adrenergic receptor blocker mainly used for the treatment of various cardiovascular disorders, such as hypertension, angina pectoris, cardiac arrhythmias, and myocardial infarction. PROP is rapidly metabolized after oral administration, and even traces of the drug may be difficult to detect in biological fluids sometime after administration. Hence its detection is of tremendous importance. A novel and sensitive modified carbon paste electrode (MCPE) employing ZnFe 2 O 4 nanoparticles (ZnFe 2 O 4 /NPs) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMITFB) ionic liquid was used for trace level analysis of propranolol (PROP) in aqueous solutions. Methods and Results: Carbon paste electrode (CPE) was modified with ZnFe2O4/NPs and BMITFB as a binder. A portion of the paste was filled firmly into one glass tube to prepare BMITFB/ZnFe 2 O 4 /NPs/MCPE. The electrochemical investigations were carried out using square wave voltammetry (SWV) and cyclic voltammetry (CV) techniques. Scanning electron microscope (SEM) and X-ray powder diffraction (XRD) studies were applied to characterize the synthesized ZnFe 2 O 4 /NPs. The obtained result shows that, the electro-oxidation signals were increased at the surface of MCPE compared to bare CPE. At pH 7.0 phosphate buffer (0.1 M), the catalytic oxidation signal exhibited a wide linear range with a low detection limit. Conclusions: It can be concluded that, the developed BMITFB/ZnFe 2 O 4 /NPs/MCPE in the current work was a promising approach for successful detection of PROP in biological and pharmaceutical samples. Keywords: Propranolol analysis, ZnFe 2 O 4 nanoparticle, Electrochemical sensor, Ionic liquid, Modified carbon paste electrode.

2,4,6-tri(3,5-Dimethylpyrazoyl)-1,3,5-triazine modified carbon paste electrode for trace Cobalt(II) determination by differential pulse anodic stripping voltammetry

In this study, a sodalite nanozeolite was synthesized and characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Following the morphology evolution of the sodalite nanozeolite in the SEM images illustrates the formation of the spherical particle with a size between 60 and 80 nm. Then, carbon paste electrode (CPE) was modified by sodalite nanozeolite and Ni2+ ions. The electrocatalytic performance of the fabricated electrode (Ni-SOD/CPE) towards glucose oxidation were evaluated by cyclic voltammetry and Chronoamperometry and it was used as anode for the electrocatalytic oxidation of glucose in 0.1 M of NaOH solution. Also, the electron transfer coefficient, the diffusion coefficient and the mean value of catalytic rate constant for glucose and redox sites of electrode were found to be 0.86, 3.13×10−5 cm2 s−1 and 5.34×106 cm3 mol−1 s−1, respectively. Good catalytic activity, high sensitivity, good choice and the stability and easy preparation enables the modified electrodes for the glucose electrooxidation. The obtained data confirmed that sodalite nanozeolite at the surface of CPE improves the catalytic efficiency of the dispersed nickel ions toward glucose oxidation. The Alkaline direct glucose fuel cells operated at ambient temperature with Ni-SOD/CPE anode created maximum power density of 4.1 mW cm-2 and cathode feed 4 mL min-1 of 0.1 M glucose and oxygen at 1 bar.

Fabrication of a novel electrochemical sensor based on an electrosynthesized indolyldihydroxyquinone as a bio-based modifier for sensitive and selective direct electrochemical determination of tryptophan

ABSTRACTA simple electrochemical sensor for dopamine was developed based on activated carbon (AC) as a modifier for carbon paste electrode (CPE). The proposed electrode (AC-CPE) was used to study the electrocatalytic oxidation of dopamine by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Firstly, the electrochemical behaviour of the modified electrode demonstrated that the substantial of the cathodic and anodic peak potentials were positively and negatively shifted, respectively; accompanied by an enhancement of current peak of DA. Then, the diffusion coefficient (D = 1.01 × 10−5 cm2 s−1) and the kinetic parameters such as the electron transfer coefficient (α = 0.48), apparent electron transfer rate constant (ks = 0.80 s−1) and catalytic reaction rate constant (kcat = 40.90 × 104 mol L−1 s−1) for dopamine at the surface of the AC-CPE were determined using electrochemical approaches. The AC−CPE showed favourable electron transfer kinetics and electro-catalytic activity towards oxidation/reduction of the dopamine. Differential pulse voltammetry (DPV) was used successfully for the determination of DA in the linear response range from 1.0 × 10−7 to 1.0 × 10−3 mol L−1 with a detection limit of 3.09 × 10−8 mol L−1. The AC−CPE offered high electro-catalytic activity in dopamine sensing individually and simultaneously in the presence of hydroquinone, catechol, paracetamol and phenol. These results demonstrated that the AC−CPE exhibited an excellent anti-interference property by peaks separation. The practical analytical utility of the AC−CPE is illustrated by dopamine determination in blood samples.

A novel ion-imprinted polymer based on pyrrole as functional monomer for the voltammetric determination of Hg(II) in water samples

A sensitive and selective electrochemical method for the determination of L-cysteine was developed using a modified carbon paste electrode (MCPE) with quinizarine. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. The apparent charge transfer rate constant, ks and transfer coefficient for electron transfer between quinizarine and carbon paste electrode (CPE) were calculated as 2.76 s−1 and 0.6, respectively. This modified carbon paste electrode shows excellent electrocatalytic activity toward the oxidation of L-cysteine in a phosphate buffer solution (pH 7.0). The linear range of 1.0 × 10−6 to 1.0 × 10−3 M and a detection limit (3s) of 2.2 × 10−7 M were observed in pH 7.0 phosphate buffer solutions. In differential pulse voltammetry, the quinizarine modified carbon paste electrode (QMCPE) could separate the oxidation peak potentials of L-cysteine and tryptophan present in the same solution, though at the unmodified CPE the peak potentials were indistinguishable. This work introduces a simple and easy approach to selective detection of L-cysteine in the presence of tryptophan. Also, the modified electrode was employed for the determination of L-cysteine in the real samples such as serum of blood and acetylcysteine tablet.

Sodium doping effect on physicochemical properties of K1−xNaxCaPb3(PO4)3 (0 ≤ x ≤ 1) for the determination of mercury(II): Application in seawater samples

A new solid‐phase extractant based on carnosine moieties covalently attached to a silica backbone (S‐Car) was introduced into a carbon paste electrode (CPE), and the resulting modified electrode (S‐Car‐MCPE) was applied to the preconcentration and subsequent voltammetric quantification of copper(II). The electrode modifier was a solid organic‐inorganic hybrid prepared by co‐condensation of tetraethoxysilane with an organotri‐ethoxysilane containing a carnosine dipeptide (β‐alanyl‐l‐histidine) derivative. This hybrid material has propensity for binding CuII species from aqueous solutions. The basic voltammetric characterization of S‐Car‐MCPE, previously loaded with CuII, indicates clearly that its electrochemical activity requires desorption of the analyte out of the solid material prior to undergoing charge transfer. A two‐step analytical procedure was then applied, involving the sequence “accumulation at open‐circuit – voltammetric detection by anodic stripping differential pulse voltammetry”. Both these steps have been optimized with respect to various experimental parameters (electrode composition, pH and composition of both detection and accumulation media, preconcentration time, detection mode, presence of interference). Linear response to copper(II) was found in the 5×10−8 M to 10−6 M concentration range, with a detection limit estimated at 4×10−9 M (0.06 ppb). This new immobilization approach for peptide‐based materials on electrode surfaces is promising for further developments of organic‐inorganic hybrids in electroanalysis.

Voltammetric monitoring of Cd (II) by nano-TiO2 modified carbon paste electrode sensitized using 1,2-bis-[o-aminophenyl thio] ethane as a new ion receptor

In this work we report preparation TiO2 hollow spheres and its application as an electrochemical sensor. Therefore the novel carbon paste electrode modified with TiO2 hollow spheres (TOHS), multi-walled carbon nanotubes (MWCNTs) and poly-glutamic acid (PGA) film (PGA/TOHS/MWCNTs/CPE) was used for simultaneous determination of dopamine (DA) and piroxicam (PRX) in the presence of ascorbic acid (AA). The electro-oxidation of dopamine(DA) and piroxicam (PRX) has been investigated by application of the modified electrode using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) methods. The modified electrode accelerates the electron transfer reactions of DA and PRX. In addition it shows no significant interference of AA as the electroactive coexistent compounds with DA and PRX in biological systems. The fabricated sensor revealed some advantages such as excellent selectivity, good stability and high sensitivity toward DA and PRX determination. Under the optimum conditions the electrode provides a linear response versus DA and PRX concentrations in the range of 0.3–60 and 0.4–80 µM and with a detection limit of 0.2µM and 0.3µM(S/N=3) respectively using the DPV method. The modified electrode was used for determination of DA and PRX in human urine with satisfactory results.

Effect of cytosine and adenine on graphene oxide for the sensing of dopamine: Electrochemical and theoretical studies

Modified carbon paste electrode with choline proline in enhancing the performance of water electrolysis system for hydrogen production

Study of kinetics aspects of the electrocatalytic oxidation of benzyl alcohol in aqueous solution on AgBr modified carbon paste electrode

A carbon paste electrode (CPE) modified with Nafion, Graphene oxide and zeolite has been prepared and characterized, and the resulting Nafion/Graphene oxide/Zeolite modified carbon paste electrode (N/G/Z/MCPE) has been applied to the electrochemical detection of Moxifloxacin hydrochloride (MOXI). It exhibited a good electrocatalytic activity in phosphate buffer (optimum at pH 7.4), as pointed out by cyclic voltammetry (CV), and N/G/Z/MCPE can be exploited for MOXI detection by chronoamperometry, electrochemical impedance spectroscopy and differential pulse voltammetry. This latter was the most sensitive one and gave rise to a linear calibration curve in the 0.04 to 250 μM concentration range, with limits of detection and qualification estimated at 1.0 nM and 3.3 nM, respectively. Contrary to previous electrochemical sensors for MOXI (e. g., CPE modified with metal nanoparticles), this new sensor can be used for multiple successive analyses without needing to refresh its surface.