Papers by Keyword: Voltammetry

Abstract: The graphite electrode was changed by applying cyclic voltammetry to electropolymerized curcumin. Then, the polycurcumin-modified graphite electrodes (GECU) were used to determine Cd²⁺ concentration. The results showed that the GECU electrodes had higher electrocatalytic activity toward Cd²⁺ than bare graphite electrodes. Furthermore, the effect of the scan rates showed that the electrochemical process controlling the redox behavior of Cd²⁺ on GECU is a diffusion-controlled electrochemical process. At Cd²⁺ ranging from 0.22 to 11.03 ppm, the relationship between oxidation peak current (Ip) and Cd2⁺ concentration follows the linear regression equation of Ip = 73.024[Cd²⁺] + 722.02 (μA, R² = 0.9936). It means that under experimental conditions, an increase in Cd2+ from 0.22 to 11.03 ppm can increase the Ip value. On the other hand, At Cd²⁺ ranging from 11.03 to 55.07 ppm, the relationship between Ip and Cd²⁺ concentration follows the linear equation of Ip = 24.227[Cd²⁺] + 1212.6 (μA, R² = 0.9920). The LOD and LOQ were determined at low Cd²⁺ concentrations, namely 0.86 ppm, and 2.84 ppm, respectively. Furthermore, the suggested modification has been used successfully and with satisfactory recoveries to determine the presence of Cd²⁺ in laboratory liquid wastewater.

Abstract: This work reports an electrochemical sensor for the quantification of the analyte, Tyramine. The 5-Amino-1-naphthol monomer is used to modify a PGE by electropolymerisation, which is used to develop the sensor. Utilizing SEM examination, Infrared Spectroscopy, cyclic voltammetry, and EIS, the morphological and electrochemical characterizations of the modified electrode were carried out. Using differential pulse voltammetry, the oxidation peaks of Tyramine is measured at potentials of 0.596 V. The linear range for Tyramine was observed from, 100 nM to 50 μM and 50 μM to 600 μM with an LOD of 89.8 nM with high sensitivity. As a result, food sample investigations may make use of this innovative, manufactured electrode.

Abstract: Portable electrochemical sensors based on noble metal nanoparticles (МеNPs) for the quantitative determination of hydrogen peroxide (H₂O₂) and sulfur-containing amino acids (cysteine, methionine, glutathione) are discussed. These sensors have high sensitivity (pM), with low sample requirements (<50 μl). This article discusses methods for producing sensors based on silver and gold nanoparticles and their application in voltammetry. It is shown that the sensitivity of H₂O₂ determination on a sensor based on silver nanoparticles (AgNPs) depends on their size. Their size is determined by the reducing agent. Sensors based on AgNPs of spherical shape with the smallest size from 0.5 to 17.5 nm have the highest sensitivity for determining H₂O₂, but a narrow range of determined concentrations. Sensors on medium-sized AgNPs have optimal metrological characteristics. Their size is from 10 to 55 nm, less sensitive, but with a wide range of determined concentrations from 0.1 to 1 nm H₂O₂. The linearity of the range of glutathione concentrations is 1.0-10.0 pM. The linearity of the range of determined concentrations of methionine is 1–26 рМ.

Abstract: This work presents an enhancement of the voltammetric signal on an electrochemical paper-based analytical device (ePAD) using a graphene oxide (GO) modified carbon electrode. The ePAD is fabricated using a screen printing technique for fabrication of the hydrophobic area and three electrode strips. The graphene film was directly prepared on ePAD by dropping 2 µL of GO dispersed in water onto the working electrode surface and leaving it to dry at room temperature. The electrochemical reduction process of GO was carried out by applying a constant voltage of -1.20 V (vs. Ag/AgCl electrode strip) in 0.1 M KCl for 800 s. The GO-modified carbon working electrode on ePAD was readily obtained and ready to use after removing KCl solution. We tested the enhancement of the voltammetric signal on ePAD with a 6 mM [Fe(CN)₆]^4–/3– redox couple in 0.1 M KCl supporting electrolyte solution. Our results obtained from cyclic voltammograms showed that the unmodified working electrode and the GO-modified working electrode on ePAD provided similar anodic and cathodic peaks. Due to accelerated electron transfer process, it was found that the GO-modified working electrode on ePAD provided approximately a 2-fold increase in voltammetric signals when compared to the unmodified working electrode on ePAD. The reproducibility (inter-day precision) of the voltammetric signal measurement using a GO-modified working electrode on ePAD was acceptable. The relative standard deviation (RSD) was 5-8%. Therefore, the GO-modified carbon working electrode on ePAD offers an effective approach to enhance the signal and sensitivity for chemical analysis.

Abstract: Marine structures and buried pipelines are constantly exposed to extreme conditions with elements such as temperature variation, soil ion content and dissolved metals posing a continuous threat on the integrity and lifespan of the structures. Quantification of these elements has been limited to studying only a few of the parameters, with the resulting corrosion behaviour not fully understood. The purpose of this study was to investigate the corrosion behaviour of carbon steel in Evian derived solution using the anodic component attained from modelled polarisation curves. The behaviour of the metal/electrolyte interface was studied using a combination of voltammetry and X-ray diffraction analysis of the mineral layer. The expression for the anodic and cathodic component of the current as a function of potential was attained from log|j| vs. potential plots. Mathematical modelling of the experimental polarisation curves was done using OriginPro Data Analysis & Graphing Software. Voltammetry around open circuit potential (VAOCP) showed the necessity for corrosion protection as the adopted electrochemical system resulted in a progressively corrosive environment. Kinetics and mechanism of the anodic and cathodic process indicated corrosion processes similar to aerated soil conditions.

Abstract: Cathodic protection induces the formation of a calcareous layer has been shown to improve metal protection against corrosion by reducing the oxygen diffusion on the metal surface. The present study focuses on the electrochemical scaling induced by the application of cathodic polarisation. A combination of non-invasive in-situ electrochemical techniques and electrochemical impedance spectroscopy was used. Metal/electrolyte interface behaviour was studied using voltammetry to determine the controlling anodic and cathodic reactions. One-week long experiments were conducted. Applied potential –1.2 V_SCE was shown to enable the formation of CaCO₃ allotropes calcite and aragonite, and brucite due to increased interfacial pH which resulted in the formation of hydrogen at the electrode surface. Time constants from bode plots for applied potential –1.2 V_SCE also illustrated the inhomogeneity of the calcareous layer. Modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. This was further validated by bode plots with the added information on the diffusion reaction process. High frequency behaviour showed a steady increase in the electrolyte resistance which may be attributed to the formation of the calcareous layer. Evidence of the initial Mg-gel porous layer, which precedes the formation of brucite, was found.

Abstract: In this study, voltammetry method for RhB determination was developed using tartrazine as sensitivity enhancement compound. The working electrode used was a molecularly imprinted poly (3-aminophenol) modified carbon paste electrodes. Measurements were conducted in 0.1 M PBS pH 7 as supporting electrolyte. RhB : tartrazine ratio of 1:10 was the best ratio for RhB determination that gave linear curve in the concentration range of 1 nM - 10 μM with a detection limit of 1.17 pM. RhB had been determined with this method in two real sample namely sekoteng and crackers. The results were similar to those found with spectrophotometry method but voltammetry method was more sensitive than spectrophotometry method.

Abstract: Cholesterol plays a crucial role in the human body. High cholesterol level in blood is a marker of CVDs. Therefore, cholesterol determination techniques are necessary for clinical practice. Currently used cholesterol determination techniques involve enzymes or expensive and complicated equipment. Electrochemical techniques are widely spread in test-systems and sensors construction. Novel modification procedure for enzymeless cholesterol determination is suggested in this study. The electrochemical behavior of cholesterol on modified electrode was studied with the usage of cyclic and differential pulse voltammetry. Obtained concentration range is linear from 0.1 up to 100 mM a conditions close to physiological (pH=6.86) with a quantification limit of 0.01 mM. Besides, the electrode surface morphology and pH-effect were studied. The developed technique is promising for the rapid determination of total cholesterol in blood.

Abstract: The electrochemical behavior of cobalt in the presence of methylviologen (MV²⁺) dichloride was investigated in choline chloride-urea (1:2 molar ratio) deep eutectic solvent containing 1 mM CoSO₄ and 1 mM MV²⁺. Cyclic voltammetry of cobalt electrolyte after reduction process at stationary potential has shown the shift of oxidation peak to cathodic region with increase of reduction process time. The investigations carried out after electrolysis of the system containing 1 mM CoSO₄ and 1 mM MV²⁺ at the reduction peak of methylviologen dichloride have shown that there was an accumulation of cobalt reduced form in near-electrode region whereas the concentration of methylviologen reduced form has not changed. This may indicate that methylviologen dichloride is a mediator in electrochemical processes with respect to cobalt in the system under consideration.

Abstract: The paper presents studies on highly porous graphene-like structures as an electrode material for supercapacitors. The experimental research was performed in inorganic (3 M sulfuric acid) and organic (1 M tetraethylammonium tetrafluoroborate in acetonitrile) electrolytes. It was found that in the inorganic medium the electrodes made on the basis of graphene-like structures possess higher specific capacitance. When increasing the potential scan rate from 5 to 100 mV/s the “electrode-electrolyte” system lost 40-80% of the capacitance. The cyclic current-voltage curves obtained for the organic electrolyte were more strongly distorted when increasing the potential scan rate, which might be related to more severe transport limitations imposed on large organic ions.