Analytical & Bioanalytical Electrochemistry
Volume:1 Issue: 1, Mar 2009

The electrochemical effects of adenosine triphosphate (ATP), guanosine 3',5'- tetraphosphate (GTP), guanosine diphosphate (GDP) and guanosine monophosphate (GMP), on the cytochrome c, were investigated with the iodide modified silver electrode in 0.01 M KNO3 at pH 7.0. Anodic and cathodic peaks were observed at 550 and 94 mV vs. Ag/AgCl, and the formal potential was calculated to be 322 mV vs. Ag/AgCl. The effects of ATP, GTP, GDP and GMP concentrations were determined on the anaerobic redox reaction. ATP led to a positive shift in the anodic and cathodic peaks of cytochrome c (Cyt c) to 599 and 141 mV, respectively. These shifts caused a facilitated-reduction reaction whilst the oxidation one became harder in the presence of ATP. GTP caused a positive shift in the cathodic peak up to 152 mV and a negative shift in the anodic peak to 495 mV, resulting in facilitated oxidation and reduction reactions of Cyt c. GDP decreased the anodic and cathodic peak currents without changing their potentials, whilst GMP did not affect the cathodic and anodic peaks of Cyt c, indicating the lack of affinity of Cyt c for this material.

Copolymers of aniline with m-chloroaniline were synthesized for different molar ratios of the respective monomers in acid medium. The structural properties of these co-polymers were characterized by using FT-IR and UV-VIS spectroscopic methods. The electrical conductivity was measured by two probe method. It was found that the conductivity of these co-polymers decreases with increase of the chloroaniline content in the copolymerization reaction. Temperature dependence of electrical conductivity data was discussed in terms of Arrhenius and variable range hopping model to elucidate the conduction mechanism. The thermal degradation of these polymers was analyzed using thermo gravimetric analysis.

The characteristics, performance and application of membrane electrode based on ion associate of diclofenac with basic dye Rhodamine 6G are described. The electrode response to diclofenac has the sensitivity of 60±1.0 mV decade-1 over the range of 5× 10-4–5×10-2 M at pH 8–11.6, and the detection limit of 2.0×10-5 M. The electrode is easy assembled at a relatively low cost has fast response time (2–4 s) and can be used for a period up to 5 months without any considerable divergence in potential. The proposed sensor displayed good selectivity for diclofenac in the presence of different substances. It was used to determine diclofenac in pharmaceuticals by means of the standard addition method. The analytical results obtained by using this electrode are in good agreement with those given by the Ukraine Pharmacopoeia.

Formal potentials of some Para-dihydroxybenzene derivatives in non aqueous solution were computed theoretically using second order Møller–Plesset perturbation theory. The calculations were carried out at the MP2 level by the continuum solvation method of PCM to mimic the role of the solvent, and obtain experimental data with the aim of cyclic voltammetry (as an electrochemical technique). The theoretical and experimental values for the formal potential of studied para-dihydroxybenzene were in agreement with each other and the average error of calculation of formal potentials was less than 0.005 V. The agreement mutually verifies the accuracy of the experimental method and the validity of the mathematical model. For the first time, the effect of electrolyte concentration in the calculation of electrode potential was considered. The results showed that with an increase in electrolyte concentration, the electrode potential slightly decreased, but these changes were not significant.

In this research the novel potentiometric sensors have been evaluated for the selective determination of Cochineal Red A (CRA) in colored food. PVC membrane (PME) and coated graphite electrode (CGE) have been prepared based on tetraphenylphosponium-CRA ion pair as the electro active substance. The electrodes reveal linear emf-pCRA responses over wide concentration ranges of (1.0×10-4-1.0×10-1 M with a slope -19.0 mV decade-1 for PME) and (1.0×10-6-1.0×10-1 M with a slope -20.2 mV decade-1 for CGE) and limits of detection of 7.8×10-5 for PME and 8.0×10-7 for CGE. The potentiometric responses were independent of the pH of the test solution in the pH range 4-7. The proposed electrodes showed very good selectivity over a wide variety interfering ions. Electrodes have been successfully applied to the determination of Cochineal Red A in food products by direct potentiometric method. The results were in good agreement with the value obtained by using the official method (HPLC measurements).