Analytical and Bioanalytical ElectroChemistry
Year:2020 | Volume:12 | Issue:1|Papers Count:10

Corrosion inhibition of mild steel by two new glassy materials correlated with the ternary system Bi2O3-B2O3-P2O5 in HCl 1. 0 M medium was evaluated using different technics: Gravimetry and electrochemical methods (polarization and electrochemical impedance spectroscopy (EIS)). The results show that the inhibition efficiency depends on the concentration of the two compounds studied (1BHP, 2BHP) and the temperature. The adsorption model obeys to Langmuir isotherm. Thermodynamic parameters were calculated and analysed. The morphology of the steel surface was characterized by scanning electron microscopy (SEM) coupled with EDX.

The corrosion inhibition performance of the natural honey in H2SO4 acidic medium containing mild steel and stainless steel, using weight loss and electrochemical techniques was investigated. The study involved the determination of the effects of the variation of the concentrations of natural honey inhibitor on the corrosion process. Potentiodynamic polarization for the electrochemical measurements was carried out by using Autolab PGSTAT 101 Metrohm potentiostat. Results obtained showed that increase in natural honey concentration (0– 10 v/v%) retards the rate of metal dissolution and hence inhibits the corrosion of the metals. And the efficiency of the natural honey inhibitor increased with increased inhibitor concentration. The Tafel plots showed that the natural honey significantly decreased the corrosion potential (Ecorr) and current density (Jcorr); but increased the surface coverage (ɵ ) and polarisation resistance. Adsorption and thermodynamics studies revealed that the Langmuir adsorption isotherm was obeyed and the large values of ∆ G ads obtained as well as its negative sign implied strong interaction and high efficiency of adsorption. SEM analysis of the metals (before and after corrosion) revealed significant reduction in corrosion rate as the concentrations of natural honey inhibitor increased.

Pharmaceutical compounds such as Cefixime (CFX) as an antibiotic were detected in water resources. These compounds in water has caused many problems including bacterial resistance to antibiotics. Some processes have been used to remove these compounds from water sources. In this research the effect of electrocoagulation process was investigated on CFX removal from water. Experiments were carried out as a batch mode in electrochemical reactor that was made from Plexiglas with dimensions of 10×15×10 cm (1 L volume) and Aluminum/Aluminum electrodes (48 cm2 effective area) that immersed vertically, monopole configuration and in parallel. Central Composite Design (CCD) utilizing a response surface methodology (RSM) was used with experimental points of pH, Initial CFX concentration, current intensity and Reaction time and employed by different model such as linear, interaction and quadratic models. The results of this study showed that the efficiency of four dependent parameters on CFX removal represent with four linear and six interactions effects that the reaction time and initial concentration of CFX have the most positive and negative effects on the removal of CFX (%), respectively. The optimum conditions for the electrocoagulation process was pH=7. 5, a primary concentration of CFX=5. 75 mg/L, a current intensity=6. 0 amperes and a reaction time=72. 5 minutes (CFX removal=85. 6%).

In this project, using a molecularly imprinting polypyrrole (MIP) modified with functionalized multi-wall carbon nanotubes (MWCNTs), a selective and sensitive electrochemical sensor constructed to measure ketorolac tromethamine (KT). Cyclic Voltammetry (CV), differential pulse Voltammetry (DPV) and chronoamperometry methods, respectively was performed in preparation of MIP, quantitative measurements and deposition of MWCNTs on the bare paper graphite electrode (PGE) surface. The nine factors were chosen for the investigation, which are: the concentration of MWCNTs, deposition time of MWCNTs onto the bare PGE surface, concentration of pyrrole, concentration of KT, number of cycles in electropolymerization, the pH of the polymerization solution, scan rate of CV process, electrode loading time, and stirring rate of loading solution. The multivariate methods, including Plackett-Burman design (PBD), and central composition design (CCD) were used for screening and optimizing of factors that could influence on the analytical response, respectively. Under the optimized conditions, the proposed MIP sensor showed a linear range from 4. 0×10-6 to 6. 0×10-3 M KT concentration with a correlation coefficient (R2) of 0. 9903. The limit of detection was obtained 0. 12 μ M (3Sb/m, n=6) with a highly reproducible response (RSD 4. 45%, n=4). The electrochemical sensor showed good results for the determination of KT in pharmaceutical and biological samples.

This work continues to focus on evaluating the electrochemical behavior of the steels Hastelloy C2000 and SAF 2205, after heat treatment in 700 ° C and 900 ° C in 1 M phosphoric acid. In addition, it reports on the effect of sulfate as a corrosion inhibitor of the two steels by using two electrochemical methods Tafel polarization and Electrochemical Impedance Spectroscopy (EIS). The electrochemical characterization of the two steels showed that the corrosion resistance decrease with the elevation of temperature from 700 ° C to 900 ° C in 1 M H3PO4. This decrease is about 76. 21% for SAF 2205 and 19. 37% for Hastelloy C2000. From these results, SAF 2205 is less resistant to corrosion than Hastelloy C2000 after heat treatment in acid environment. The comparison of the behavior of the two steels in the presence of sulfate showed that the corrosion current intensity of SAF 2205 is higher than that of the Hastelloy C2000. However, the separate analysis of each steel showed, an inhibitory efficiency of 99. 99% with the addition of 0. 1 g/l of SO42-for Hastelloy C2000 and about 91. 06% for 0. 2 g/l of SO42-for SAF 2205 as optimums concentrations.

This paper reported a selective and sensitive electrochemical approach for detection of rhodamine B (RhB) in real samples based on a multi-walled carbon nanotubes paste electrode (MWCNT/CPE). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronocoulometry were used to investigation of electrochemical behavior of RhB. The modified electrode showed an excellent electrocatalytic property toward the oxidation peak current of RhB. Analytical parameters such as linearity, selectivity, repeatability, and stability are also investigated. After optimizing the experimental conditions, the anodic peak current of RhB was linear to its concentration in the range of 0. 1– 15. 0 μ M, and the limit of detection was 20. 0 nM (S/N=3) in 0. 1 M phosphate buffer solution (pH=3. 0). Furthermore, the proposed sensor was successfully applied for the detection of RhB in real samples (water samples and Hair colors) with the recoveries of 95. 0– 110. 0%, indicating a promising potential in practical application.

Herein, we report simultaneous electrochemical determination of Paracetamol (PAR) and Caffeine (CAF) at activated glassy carbon electrode (aGCE) using cyclic voltammetry (CV) and square wave voltammetry (SWV). Comparison was made for cyclic voltammetric response of PAR and CAF at bare glassy carbon electrode (bGCE) and aGCE in 0. 1 M phosphate buffer solution (PBS) of pH 7. 0. The experimental result showed that the redox process of PAR was both diffusion and adsorption controlled, whereas the oxidation reaction of CAF is diffusion controlled at aGCE. The aGCE showed a linear response to PAR in the concentration range of 10-180 μ M when the concentration of CAF was kept constant (25 μ M). Similarly, the linear range for CAF was from 10-95 μ M at a constant concentration of 10 μ M PAR. The detection limit (LOD) of PAR and CAF was found to be 2. 55 μ M, 2. 36 μ M (3σ /m), respectively. The validity of the demonstrated method was checked by using commercial tablet which contain different amount of PA and CAF and satisfactory percent recoveries were obtained.

Materials of ultrafine– grained (UFG) have attracted great attention in the last twenty years. Some severe plastic deformation (SPD) procedures have been utilized for producing UFG materials in which the accumulative roll bonding (ARB) process acts as the most effective procedure among them. UFG Structure demonstrates a progress in mechanical properties in addition to different corrosion behavior. Nevertheless, it does not always lead to better corrosion resistance. Various relevant investigations will be reviewed in this paper to consider semiconducting behavior of UFG Cu that has been produced by ARB process. Analysis of Mott– Schottky (M– S) is a major in-situ method to analyze semiconductor properties of passive layers. Thus, the effect of grain size arising from ARB process on copper semiconducting behavior has been evaluated in relevant passive media by M– S analysis in this study.

In this report, a new electrochemical sensor was developed for sertraline (STR) analysis. The sensor was prepared based on modified Pt electrode with graphene nanoparticles and molecular imprinting polymer (MIP) by coating a very thin layer of polymer onto a support. Through this approach, all of the binding sites of the polymer immobilized on the electrode surface are available for target molecules. The STR binding experiments indicated that the sensor modified by MIP have much higher adsorption ability than non− imprinted polymer (NIP) based sensor. Also, using of graphene in preparation of Pt electrode leads to a significant improvement in response of electrode because of their high electrical conductivity and large surface areas as the platform of the polymer that makes the graphene-MIP an excellent electrical transducer for direct electrical sensing. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) tests were used to evaluate the performance of the electrochemical sensor. Some parameters affecting the sensor performance such as MIP suspension, extraction pH and preconcentration time were optimized and under optimal conditions, the modified sensor with MIP-graphene showed linear responses with STR concentration in the range of 1. 0×10-8 to 1. 0×10-6 mol L-1 (R2 = 0. 985) with a detection limit of 7. 0×10-9 mol L-1. This developed sensor with the MIP was consequently capable of selective sensing of STR in human serum sample with recovery values in the range of 98. 2-103. 5%.

After modifying an electrogenerated chemiluminescence sensor with a Ru(bpy)32+/Sm2O3 Nanoparticles(NPs)/chitosan composite, the resulting electrode was used as a sensitive tool for the detection of phenylalanine. The electrochemiluminescence (ECL) signal resulting from the electrochemical interaction between tris(2, 2-bipyridyl) ruthenium(II) (Ru(bpy)32+) and the analyte on the surface of the modified sensor. The presence of the Sm2O3NPs was found to enhance the ECL signal. Further the influences of Ru(bpy)32+ concentration, potential scan rate and solution pH on the intensity of the signal were monitored and optimized. The method showed a linear response in the range of 5. 0×10-11 to 5. 0×10-7 M (R2=0. 9824) with a detection limit of 1. 4×10-11 M. The modified ECL sensor was further used for the analysis of phenylalanine in human serum samples and an RSDs of 4. 4% was observed, proving the high sensitivity, selectivity, and good stability of the sensor.