سال:1397 | دوره: | شماره: |تعداد مقالات:10

In this research, an ionic liquid modified carbon paste electrode was prepared by incorporating 1-hexyl-3-methylimidazolium hexafluorophosphate (HMHP) to a carbon paste. The preconcentration and electroanalysis of riboflavin were employed using the HMHP modified carbon paste electrode (HMHP/CPE). The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the voltammetric measurement. During the preconcentration step, riboflavin was adsorbed onto HMHP surface. The influence of various experimental parameters on the HMHP/CPE response was investigated (i. e. pH, accumulation time, pulse time and pulse amplitude). Under the optimized conditions, the reduction peak showed that the peak height was found to be directly proportional to riboflavin concentration in the range comprised between 3. 5×10-8 M and 1. 5×10-6 M. With this, it was possible to determine limit of detection, which resulted in 11 nM. Common interfering species did not interfere in the determination. The method was successfully applied to the measurement of riboflavin in pharmaceutical formulations.

Herein, Poly (Congo red) modified carbon paste electrode was prepared by electropolymerization method. The poly (Congo red) modified carbon paste electrode showed an excellent electrocatalytic effect on the oxidation of Norepinephrine (NE) in phosphate buffer solution (pH 7. 4) at the sweep rate 100 mV/s. Some electrochemical parameters like sweep rate, different concentrations and effect of pH were studied. The limit of detection of NE was found to be 0. 29 μ M in the linear range of 30 to 90 μ M by CV method. The simulations determination of NE, PA and FA in their sample mixture was analyzed by using cyclic voltammetric technique. The differences of the oxidation peak potentials for NE– PA and PA– FA were about 0. 212 V and 0. 323 V in cyclic voltammetric at 100 mV/s respectively. The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of Paracetamol (PA) and Folic acid (FA). This work provides a simple and easy approach to selectively determine NE in the presence of PA and FA.

In this study, a potentiometric cobalt selective membrane sensor was prepared based on 1-(6-choloroquinoxaline-2-yl) hydrazine as a new ionophore. At first, the lowest-energy conformer of 1-(6-choloroquinoxaline-2-yl) hydrazine molecule (Ligand) and four local structure minima corresponding to their complexes with various ions were obtained using density functional theory (DFT). The calculated results of the Gibbs free energy of the reaction at B3LYP/6-31G(d) level show that the thermodynamic reactivity of complexation of cobalt ion (Co2+) with studied ligand is the best. Finally, a liquid membrane electrode for potentiometric monitoring of ultra-trace amounts of Co2+ was prepared by using this ligand. The electrode exhibits a Nernstian response for Co2+ ion over a wide concentration range of 1. 0×10-1 to 3. 0×10-6 mol L-1. The limit of detection of the sensor is 1. 0×10-6 mol L-1. The sensor has a relatively fast response time (~10 s) and a useful working pH range of 3. 0-8. 0. Interferences of some cations were also evaluated. It was used as an indicator electrode in potentiometric titration of Co2+ with EDTA and in indirect determination of vitamin B12 in pharmaceutical samples. The results indicate that this electrode is sensitive for determination of Co2+ and vitamin B12.

A non-enzymatic glucose sensor was successfully developed based on platinum (Pt) particles immobilized on Pt electrode modified with polyaniline film (PANI) modified Pt electrode. The optimal conditions for maximum dispersion of Pt particles on PANI were evaluated. The electrochemical behavior of the Pt/PANI/Pt sensor towards oxidation of glucose was studied in both alkaline (NaOH) and neutral (PBS) electrolytes using cyclic voltammetry and chronoamperometry techniques. The sensor showed a wide linear response to the glucose concentration from 0. 1 mM to 12 mM with linear regression coefficient of 0. 997. Furthermore, high sensitivity of 215. 8  A mM-1cm-2 is obtained with fast response time of less than 2 s. The as prepared sensor showed good stability, excellent reproducibility, and high selectivity to only glucose in presence of interferents. Finally, the applicability of the sensor was successfully verified with detection of glucose in juice samples. The results obtained were in good agreement with commercial glucose meter. These observations indicate that our sensor is promising in the field of non-enzyme based glucose sensors.

The current work focuses on the development of a sensitive and selective electrochemical device based on a graphite screen printed electrode modified with indium(III) mixed-ligand nanocomplex (In(III) nanocomplex/SPE) for the analysis of amlodipine. The studies proved the sensor to have excellent electron-mediating behavior in the oxidation of amlodipine in a 0. 1 M phosphate buffer solution (PBS) (pH 7. 0), and the response of the sensor was found significantly depend on the charge and structure of the analyte. The detection limit of the method for amlodipine was 0. 2 μ M (S/N=3) and the response was found to be linear in the concentration range of 1. 0 to 500. 0 μ M. The modified electrode was use for the detection of amlodipine in real samples and found to produce satisfactory results.

The new synthesized polymer named pentaglycidyl ether penta-ethoxy phosphorus (PGEPEP) was tested in the behavior of the coating on the metal substrate in a marine environment. In the first step, we developed hybrid composites by collecting two charges respectively trisodium phosphate and natural phosphate. In the second step, we applied the different hybrid composites F1 (PGEPEP/TSP), F2 (PGEPEP/NP) and F3 (PGEPEP/TSP+NP) combined from epoxy resin and synthetic filler, natural load and both sets on E24 carbon steel in 3. 5% NaCl. Finally, the gravimetric and electrochemical measurements of the composite F3 (PGEPEP/ TSP+NP) are very encouraging and reach a maximum efficiency respectively equal to 93%, 95% and 92%.

In this study, a new modified electrode was proposed to measure ascorbic acid. Graphite screen printed electrode was modified with NiFe2O4 nanoparticles (NiFe2O4/SPE). Cyclic voltammetry (CV), Chronoamperometry (CHA) and differential pulse voltammetry (DPV) methods were used to analyze the prepared electrode. The catalytic property resulting from the synergistic effect of this modifier not only increased the oxidation current but also reduced the oxidation potential of ascorbic acid. Scan rate and pH effects on the performance of NiFe2O4/SPE were also investigated. The linear calibration curve of ascorbic acid was obtained within the linear range of 5. 0×10− 7– 1. 0×10− 4 M, and the detection limit was calculated as 1. 0×10− 7 M. Finally, the modified electrode was successfully used to measure ascorbic acid in some real samples.

This work is devoted to examining the effectiveness of aqueous extracts of olive flower pre-anthesis, anthesis and grain pollen olive (Olea europaea L. ) on corrosion of mild steel in 1 M HCl solution; The weight loss measurements, polarization curves and electrochemical impedance spectroscopy (EIS) infrared spectroscopy methods were employed to evaluate corrosion rate and inhibition efficiency. The corrosion inhibition efficiencies of olive flower inflorescence pre-anthesis, anthesis and grain pollen are achieved 94%, 95. 9%, and 94. 8% in 1 M HCl, respectively. The inhibition efficiency is greatly reduced as the temperature is increased; the experimental results show that corrosion inhibition efficiency increases with concentration of the sample extract; polarization studies show that olive flower inflorescence pre-anthesis, anthesis and grain pollen extracts acts as a mixed inhibitor.

A Cu(II) nanocomplex, [CuCl2(salophen)]. H2O[salophen=o-phenylenediaminebis(salicylidenaminato)], was synthesized. The electrochemical properties of the as-prepared Cu(II) nanocomplex modified graphite screen printed electrode (Cu/SPE) were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Moreover, as a nanosensor for the determination of norepinephrine the Cu/SPE exhibited excellent electrocatalytic activity for the oxidation of norepinephrine with a faster electron-transfer rate. The DPV technique was used for the trace determination of norepinephrine. The dependence of current vs. concentration was linear from 0. 3 to 300. 0 μ M with a regression coefficient of 0. 9992, and the detection limit of norepinephrine was 0. 09 μ M. Finally, the method was applied to the selective and precise analysis of norepinephrine in norepinephrine injection.

In this study, the effect of the formulation derived from Ceratonia siliqua L, (noted FCSL) as green corrosion inhibitor of iron in solution simulated to the rain water (at pH=3. 6) was examined by using the weight loss, the potentiodynamic polarization and the electrochemical impedance spectroscopy measurements. In addition, determination of the physico-chemical indexes of the seeds oil of Ceratonia siliqua L, showed that it is a long chain unsaturated oil. The results indicated that the inhibition efficiency (% IE) of the FCSL formulation increased with increasing both inhibitor concentrations and immersion time. The inhibition efficiency reached a value of 98. 6% at 750 ppm of the FCSL formulation. This formulation may be form a filmed and acts as a barrier, which minimize the contact area between metallic surface and corrosive solution. This leads to decrease the oxidation of the iron substrate. The metallic surface, after inhibitor treatment has been observed using SEM coupled with the EDX analysis. The obtained results indicate that the FCSL acts as an excellent mixed-type inhibitor.