Analytical & Bioanalytical Electrochemistry
Volume:11 Issue: 2, Feb 2019

A sensitive electrochemical sensor was assembled by the electropolymerization of bromocresol purple on the surface of multiwalled carbon nanotubes modified carbon paste electrode i.e., poly(BC/MWCNTs)CPE. The surface network of the newly constructed electrochemical sensor was recorded by scanning electron microscope. The developed sensor has demonstrated improved electrocatalytic activity towards sulfanilic acid detection in presence of 0.1 M phosphate buffer solution at pH 7.5. The experimental parameters including the effect of scan rate, buffer pH and analyte concentration were optimized systematically. A linear relationship was found between the peak currents and analyte concentrations with limit of detection and limit of quantification values 0.98×10-7 M and 3.2×10-7 M respectively, which are significantly lower than the reported methods. The kinetic parameters such as reaction rate constant (ks), charge transfer coefficient (α), total number of electrons transferred (n) were evaluated and found to be 0.269, 3.27 and 2.0 respectively. The results deduced that the modified poly(BC/MWCNTs)CPE provides high sensitivity, good stability, excellent catalytic activity and better reproducibility along with lower limit of detection for the analysis of sulfanilic acid.

In the present study, copper ion has been separated from Phosphate Buffer Solution by 2-Amino-N-(2-Pyridyl Methyl)-Benzamide as an organic ligand through a flat type Supported Liquid Membrane (SLM). To this end, the organic ligand was dissolved in various solvents, and then the Polytetrafluoroethylene (PTFE) membrane was immersed in the resulting solutions for 24 h. Before extraction step, solvents with best performances including Ethanol and benzyl acetate were selected as solvent and as plasticizer, respectively. The optimized complexing reagent concentration on the membrane was 0.05 M. The adjusted pH was 4.5 and concentration of Cu solution was 1×10-3 M for feed solution, respectively. Copper ion was then determined using Fast Fourier Transformation Continuous Stripping Cyclic Voltammetry (FFTCCV) technique by a Carbon Paste Electrode (CPE). PTFE with 0.1 μm pore size have more permeability than 0.2 μm. Based on the obtained results, effective parameters imposing sensitivity of copper ion measurement were finally investigated at pH 3.2, at scan rate of 10 mV.s-1, stripping time of 0.1s and potential of -600 mV. Limit of detection of 0.19 μM for copper ion in optimized condition was attained. Under the optimized conditions the recovery of Copper ions from real samples were studied and recovery percentage were 45.71%, 34.28% and 22.58% for tap water, river water and sea water respectively.

Simple, precise, inexpensive and sensitive voltammetric method was developed for simultaneous determination of Ramipril (RAM) and felodipine (FLD) mixture in drug substance, drug product and human urine using carbon paste electrode (CPE). Effect of different surfactants on peak current was studied in acetate buffer solution of pH 4.8. Sodium dodecyl sulphate (SDS) is the optimum surfactant based on the enhancement of the peak current. The peak current varied linearly over the concentration ranges from 5×10-5 mol L-1 to 8×10-4 mol L-1 for both drugs. The quantification limits were 1.78×10-5 and 1.94×10-5 mol L-1 and detections limits were 4.5×10-6 and 2.7×10-6 mol L-1 for RAM and FLD, respectively. The proposed voltammetric method was successfully applied to determine RAM and FLD mixture in drug product and human urine. The results of the proposed method were statistically compared with those of the reported method and showed no significant difference. Thus, it can be applied for quality control of both drugs.

The objective of this work is the development of a new green inhibitor extracted from Aloe vera (L.) Burm. F. (syn. Aloe barbadensis Mill.) for the corrosion inhibition of bronze B66 in a neutral chloride environment (3%NaCl). The tannins extract was obtained from the green rind of Aloe vera by maceration process method. The major compound of the TAV is Linolenic acid (16.59%). The study of the tannins extract from Aloe vera (TAV) was carried out by coupling gravimetric and electrochemical (stationary and transitory) methods, namely the plot of the polarization curves and electrochemical impedance diagrams. Surface analysis of bronze samples was performed using an SEM (scanning electron microscope) coupled to EDS (energy dispersive X-ray spectroscopy), which helped to highlight the protective effect of the TAV studied. The experimental results obtained allowed to note that the inhibition efficiency reaches 89% at 150 ppm of TAV in 3%NaCl. This inhibitor acts by modifying the mechanism of the processes involved at the interface Bronze/3%NaCl.

In this paper, magnetic iron oxide nanoparticles capped with glucose/sucrose/starch have been synthesized though a simple and easy electrochemical method. In this method, OH– anions were produced via galvanostatic cathodic current on the cathode surface, and then reacted with metal cations (i.e. Fe2+, Fe3+ and Ni2+) to form Ni-doped Fe3O4 deposit. At the same electrochemical conditions, saccharides capped Ni-doped iron oxides were also synthesized from saccharide-added electrolyte. The prepared samples were specified using FE-SEM, XRD, VSM, FT-IR and thermal gravimetric analyses. The FT-IR, XRD and FE-SEM data approved the formation of Ni-doped Fe3O4 particles with size of 30 nm. In the TG profiles, the sharp weight loss (15.5%wt.) at the temperatures of 150-300 oC proved the capping of iron oxide surfaces by saccharide layer. The measured magnetic data by VSM analyses indicated that the prepared samples exhibit high saturation magnetization and low remanence at the applied external fields, and have proper superparamagnetic characters.

The properties of a glassy carbon electrode (GCE) were modified using reduced graphene oxide (rGO) for use in the analysis of levofloxacin (LEV). The behavior of the modified GCE (mGCE) were assessed based on cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and UV-Vis spectroscopy, and its surface was studied through scanning electron microscopy (SEM) tests Electrochemical measurements were performed using the electrode in differential pulse voltammetry (DPV) and CV experiments. The operational factors affecting the results, including the potential scan rate, the pH of the solution, were evaluated and optimized. The linear range for LEV determination were from 100 to 3000 μM and 0.2 to 100 μM. The limit of detection of the electrode was 6.0×10−8 M. The modified electrode by rGO demonstrated a number of advantages: a simple preparation route, high sensitivity and excellent reproducibility. The mGCE was used to determine LEV in serum samples and the results were acceptable.

Nickel molybdate (NiMoO4) nanopowders were prepared by a new method in low temperature. For the first time, we used carboxymethyl cellulose as a new capping agent in synthesis procedure. The formed nickel molybdate products have been characterized by means of UV–vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray microanalysis (EDX). Glassy carbon electrode modified with NiMoO4 nanopowders was prepared and used for oxidation of ethanol and methanol. The study of the different scan rates indicates a diffusional process for oxidation of ethanol. The detection limit obtained for ethanol was also 3.8 mM.

Supercapacitors (SCs) are promising energy sources with high power densities. In the recent years, many efforts have been made to enhance the low energy density of SCs through improvement of the electrode materials. As electrode materials, metal oxides/hydroxides (MOHs) and their composites usually offer high energy densities as a result of their high theoretical capacitances. Up to now, various synthetic methods have been developed for preparing MOHs. In this regards, cathode electrodeposition through base electrogeneration has been intensively used as a one-step simple technique for obtaining various nanostructures of MOHs composites as high-performance SC electrode materials. In this paper, the reports on the fabrication of MOHs-based nanomaterials through the CED method and their super-capacitive abilities have been reviewed.

In this paper, a novel nanocomposite based on the magnetite nanoparticles and three-dimensional nitrogen doped porous graphene was fabricated. In this way, a typical galvanostatic electrosynthesis was carried out in the aqueous bath with composition of Mn chloride, ion chloride, iron nitrate and nitrogen doped porous graphene. The XRD data proved the magnetite phase of the deposited iron oxide onto nitrogen doped porous graphene. It is also observed that the fabricated sample has composed of Fe3O4 nanoparticles with Mn2+ doped cations in their crystal structures. VSM measurements indicated that the Mn doped iron oxide/ nitrogen doped porous graphene composite exhibits superparamagnetic behavior, and have saturation magnetization, remanence magnetization and coercivity of Ms=33.45 emu g–1, Mr=0.26 emu g–1 and Hci=2.41G, respectively. Compared with naked iron oxide and metal-ion doped iron oxide nanoparticles, the composite showed better superparamagnetic performance (i.e. lower Hci and Mr), which was related to well-dispersion of particles onto porous graphene and their single domain magnetic behavior.

In this paper, 2-(4-methyl pyperazine-1-yl methyl)-1-cyano cyclohexanone was synthesized and used as an ion carrier in Cu2+ ion selective sensor. The potentiometric sensor was worked well in a concentration range of 1.0×10-2 to 1.0×10-6 M of Cu2+ ions with Nernstian slope of 30.7±0.6 mV/decade. Workable pH range of the sensor was 3.5-8.5 and the response time of the electrode was about 10 s. Detection limit of the electrode was obtained 1.0×10-6 M. The sensor has a relatively fast response time (∼10 s) and a useful working pH range of 3.5-8.5. The proposed electrode responded to copper ions selectively respect to other common metal cations. Performance of the copper electrode as an indicator electrode was checked in a potentiometric titration of Cu2+ ions with EDTA as titrant which confirmed the monitoring ability of the copper selective sensor. Finally, direct determination of Cu2+ ions in some river water samples was done to show the analytical ability of the designed sensor.