Analytical & Bioanalytical Electrochemistry
Volume:6 Issue: 1, Feb 2014

In this study, the electrochemical behaviour of 2-thiouracil (2TU) has been investigated using cyclic, differential pulse and square wave voltammetric techniques. The electrochemical studies were carried out in pH 3 with 0.2 M phosphate buffer as supporting electrolyte. Cyclic voltammetric studies were performed in a wide range of sweep rates and various concentrations of 2TU. The effect of surfactants was studied. The anodic peak was characterized and process was adsorption-controlled. According to the linear relation between the peak current and the 2TU concentration, differential-pulse voltammetric method for the quantitative determination in pharmaceuticals was developed. The linear response was obtained in the range of 1–11 μM with a detection limit of 2.05×10-8 M with good selectivity and sensitivity. The proposed method was successfully applied to 2TU determination in pharmaceutical samples and for the detection of 2TU in urine as a real sample.

In this study, Taguchi method has been used for optimization of chromium(VI) electroplating process and for this purpose brass materials have been electroplated under different conditions of the process to study their effects on throwing power of chromium deposit. Finally the results of main effects plot and analysis of variance showed that among the influential factors in this process, only current density of 4 A/dm2 and time of 4 minutes have the most effects in the characteristics of the response. Also SEM images confirmed that the crack density on the surface of Cr-deposit is decreased under the mentioned conditions.

The interactions between oxyphenonium bromide (OXBr) and two precipitating reagents, silver nitrate (AgNO3) and phosphomolybdic acid (PMA) have been studied by conductometric and spectroscopic techniques. The equilibrium constant, the solubility product constant and other functions related to the process of precipitating OXBr were calculated exploiting the conductometric procedure. Furthermore, new approaches towards equivalence point detection have been pursued. In this itinerary, differential conductivity methods and Boltzmann sigmoid fitting model were found to be more appropriate compared to the conventional routine. The described procedures allowed the determination of OXBr within the range of 1-20 mg using both reagents. The molar combining ratio reveals that (1:1) (drug: reagent) ion associates are formed for both reagents with OXBr. Moreover, the obtained precipitate has been spectroscopically characterized using IR and 1H-NMR. The proposed conductometric method was applied successively to pharmaceutical formulations containing OXBr and the results obtained were favorably compared with those obtained using the reference conductometric method.

A novel method for determination of tyrosine in flow-injection systems has been developed. A europium oxide nanocomposite carbon paste electrode was used to improve the sensitivity of the electrode response. Signal to noise ratio has significantly increased by application of discrete FFT method, background subtraction and current-time integration of the electrode response over a selected potential range. The effects of various parameters on the sensitivity of the method studied. The best response was obtained in pH=7.0, potential scan rate=1 Vs-1, accumulation time=0.5s, and accumulation potential=-500 mV. Detection limit was 6.6×10-9 mol L-1 of tyrosine. The technique has good accuracy and high sensitivity.

A novel carbon paste electrode modified with carbon nanotubes and 5-amino-2',4'- dimethoxy-biphenyl-2-ol (5ADMB) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for electrocatalytic oxidation of ascorbic acid, is described. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various scan rates. The apparent charge transfer rate constant, ks, and transfer coefficient, α, for electron transfer between 5ADMB and carbon nanotubes paste electrode were calculated as 7.94 s−1 and 0.5, respectively. The electrode was also employed to study the electrocatalytic oxidation of ascorbic acid, using cyclic voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. It has been found that the oxidation of ascorbic acid at the surface of modified electrode occurs at a potential of about 250 mV less positive than that of an unmodified CPE. The diffusion coefficient, electron transfer coefficient, and heterogeneous rate constant, for oxidation of ascorbic acid at the modified electrode surface were also determined. Square wave voltammetry (SWV) exhibits a linear dynamic range from 1.0×10-6 to 7.5×10−4 M and a detection limit of 0.1 μM for ascorbic acid. Finally this modified electrode was used for determination of ascorbic acid in real samples.

In this study, a carbon paste electrode modified with carbon nanotubes and benzoylferrocene (BF) was used to prepare a novel electrochemical sensor. The objective of this novel electrode modification was to seek new electrochemical performances for the detection of glutathione. The response of catalytic current with glutathione concentration showed a linear relation in the range from 1.0×10−7 to 1.0×10−4 M with a detection limit of 3.0×10−8 M. Finally, this method was used for the determination of glutathione in real samples.

Electrocatalytic transformation of barbituric acid, aldehyde and malononitrile in ethanol in an undivided cell in the presence of potassium bromide as an electrolyte results inthe formation of substituted pyrano[2,3-d]pyrimidinones at room temperature in 65-85%yields. The progress and completeness of electrolysis were monitored by cyclic voltammetry (CV). The voltammograms were recorded with μAutolab FRA2 Potentiostat-Galvanostat. A three-electrode system was used with a platinum rod as working electrode, a GC electrode as the counter electrode and an Ag/AgCl as the reference electrode. The structure of products was characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. In this electrosynthesis, the first step is electrochemical that follows by chemical reaction. Therefore the proposed mechanism is EC.

The electrochemical behaviour of hydrazine studied at the surface of 1-[4-(ferrocenyl ethynyl) phenyl]-1-ethanone (as an organo-metallic mediator) modified carbon paste electrode in aqueous media using cyclic voltammetry (CV) and double step potential chronoamperometry. It has been found, that under optimum condition (pH 8.00) in cyclic voltammetry, the oxidation of hydrazine is occurred at a potential about 300 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and the catalytic reaction rate constant, k/h were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of hydrazine showed a linear dependent on the hydrazine concentration and the linear calibration plots were obtained in the ranges of 7.0×10-5 M - 1.8×10-2 M and 8.0×10-6 M - 1.0×10-3 M of hydrazine concentration with CV and differential pulse voltammetry (DPV) methods, respectively. The detection limits (2σ) were determined as 1.4×10-5 M and 1.2×10-6 M by CV and DPV methods. The RSD% for seven replicates determination of 20.0 and 50 μmol L-1 of hydrazine were 1.8 and 1.6%, respectively. This method was also examined as a selective, simple and precise new method for voltammetric determination of hydrazine in real sample.

The electrochemical behavior of a multiwalled carbon nanotube paste electrode modified with 2-((7-(2, 5-dihydrobenzylideneamino) heptylimino) methyl) benzene-1, 4-diol (DBHB) was studied. The pH dependent, apparent charge transfer rate constant and transfer coefficient were investigated for the electrochemical behavior of DBHB. This electrode showed high electrocatalytic activity toward oxidation of epinephrine (EP) relative to an unmodified carbon paste electrode. Cyclic voltammetry and chronoamperometry were used to study the electro-oxidation of EP at the modified electrode and electrocatalytic mechanism, catalytic rate constant and diffusion coefficient was obtained for oxidation of EP. Using differential pulse voltammetry (DPV) a highly selective and simultaneous determination of EP, acetaminophen (AC) and folic acid (FA) has been obtained at the modified electrode as an electrochemical sensor. The present method provides a simple method for selective detection of EP in biological samples.

This paper presents pulse potential electrodeposition of platinum nanoparticles on fluorine doped tin oxide (FTO) from AlCl3-NaCl molten salt containing K2PtCl6 at 393K. The results showed that by optimizing the deposition parameters including the on potential, off potential, on time and duty cycle we are able to improved catalytic performance of PtNPs/FTO modified electrode for ethanol electrooxidation. The two- level factorial design was used to screen and optimize the pulse potential electrodeposition variables. The prepared PtNPs/FTO electrodes were characterized by scanning electron microscopy, Energy-dispersive X-ray spectroscopy and cyclic voltammetry. The prepared PtNPs/FTO exhibited high performance in the electrocatalytic oxidation of ethanol in alkaline solution.