In-situ circular dichroism spectroelectrochemical study on the redox process of norepinephrine

The redox process of norepinephrine in pH = 7.0 phosphate buffer solution at glassy carbon electrode was studied by circular dichroism spectroelectrochemistry with a long optical path thin layer cell. The spectroelectrochemical data were analyzed with the double logarithm method. According to the double logarithsmic plot results, the mechanism of electrochemical oxidation of norepinephrine is an irreversible process with a subsequent chemical reaction (EC) to form a norepinephrinechrome. Both of norepinephrinequinone and norepinephrinechrome are followed E mechanisms. Some kinetic parameters about the electrochemical process, i.e. the electron transfer coefficient and number of electron transfered, alpha n = 0.38, the formal potential, E-1(0)' = 0.20 V, the standard heterogenous electron transfer rate constant, k(1)(0) = 1.2 x 10(-4) cm s(-1) for the oxidation of norepinephrine, alpha n = 0.37, E-2(0)' = 0.25 V and k(2)(0) = 4.4 x 10(-5) cm . s(-1) for the reduction of norepinephrinequnone and alpha n = 0.33, E-3(0)' = -0.25V and k(3)(0) = 1.1 x 10(-4) cm . s(-1) for the reduction of norpinephrinechrome, were also estimated.

Study of electrochemical behavior of ergosterol by in situ thin layer circular dichroic spectroelectrochemistry

The electroxidation of ergosterol was studied by in situ circular dichroic (CD) spectroelectrochemistry with a long optical path length thin layer cell. It was confirmed that the oxidation of ergosterol in ethanol solution is a two-electron irreversible electrochemical process with strong adsorption of an electroinactive product at the glassy carbon electrode, which blocks the electrochemical reaction. The CD spectroelectrochemical data were treated by the double logarithm method together with nonlinear regression, from which the formal potential, E-0 = 1.00 V, alpha n(alpha) = 0.302, the standard electrochemical rate constant, k(0) = 6.1(+/-0.4) x 10(-4) cm s(-1) and the adsorption constant, beta = 19 +/- 1, were obtained. The number of electrons transferred (n = 1.86) was estimated by cyclic voltammetry.

In-situ microscopic FTIR spectroelectrochemistry of ascorbic acid in poly(ethylene glycol)/LiClO4 electrolyte paste and in the presence of dispersed cobalt hexacyanoferrate microcrystalline powder

In-situ microscopic FTIR spectroelectrochemical technique(MFTIRs) was applied to studying the electrochemical oxidation of ascorbic acid(AA) in poly(ethylene glycol)(PEG) paste at a 100 mu m diameter Pt disk electrode. Using this technique, the catalytic ability of cobalt hexacyanoferrate(CoHCF) microcrystalline toward AA oxidation was also studied, it was found that the dispersed CoHCF powder in the PEG paste can generate well-shaped thin-layer cyclic voltammetric waves with the peak height proportional to the scan rate, corresponding to the Fe centered redox reactions. This oxidation step catalyzed the AA oxidation. Also, this pasted CoHCF powder generated well-resolved in-situ MFTIRs spectra, by which a chemical interaction between C = C bond of AA ring and CoHCF lattice was revealed. A corresponding surface docking mechanism for the catalytic reaction has been proposed.

In-situ microscopic Fourier transform infrared spectroelectrochemistry of redox mechanism for electroactive species in polyelectrolyte

Studies for the development of the in-situ microscopic FTIR spectroelectrochemistry (MFTIRS) have been carried out in polyethylene glycol(PEG) polyelectrolyte, Redox reaction mechanisms of various electroactive substances involving inorganic salt, organic compound and inorganic polymeric particles have been studied.

Investigation of the self-accelerating process of ascorbic acid by in-situ circular dichroism spectroelectrochemistry

The electrode reaction process of ascorbic (Vc) was studied by in-situ circular dichroic(CD) spectroelectrochemistry with a long optical path thin layer cell on glassy carbon(GC) electrode. The spectroelectrochemical data were analyzed by the double logarithmic method together with nonlinear regression. The results suggested that the mechanism of Ve in pH 7.0 phosphate buffer solution at GC electrode was a two-electron irreversible electrooxidation followed by adsorption of the oxidation product. That is a self-accelerated process. Some kinetic parameters at free and at adsorbed electrode surface, i.e, the formal potentials, E-0' = 0.09 V, E-a(0') = 0.26 +/- 0.02 V; the electron transfer coefficient and number of transfered electron, alpha n = 0.41, alpha(a)n = 0.07;the standard heterogeneous electron transfer rate constant, k(0) = 8.0 x 10(-5) cm.s(-1), k(a)(0) = 1.9 x 10(-4) cm.s(-1) and adsorption constant, beta = 102.6 were also estimated.

Influence of cation concentration on 7,7,8,8-tetracyanoquinodimethane in polyelectrolyte by using in-situ microscopic Fourier transform infrared spectroelectrochemistry

The ion pair between the dianion of 7,7,8, 8-tetracyanoquinodimethane(TCNQ) and Li+ were investigated by in - situ microscopic Fourier transform infrared( FTIR) spectroelectrochemical technique. The effect of ion pair increases with increasing the concentration of cation. We observed a new band at 2130 cm(-1).

Preparation and luminescence properties of terbium-Sal complex in-situ synthesized in silica matrix by a two-step sol-gel process

In-situ synthesis of terbium complex with salicylic acid (Sal) in silica matrix was made by a two-step sol-gel process. The terbium complex with salicylic acid was formed in sol-gel derived silica gel, and confirmed by the luminescence excitation spectra and infrared(IR) spectra. As compared to the pure terbium complex powder, the silica gel containing terbium complex exhibits its characteristic emission and presents a longer fluorescence lifetime than that for the pure complex. The luminescence properties of the complex containing;silica gel were investigated and compared with that of both terbium doped the silica gel and thp pure complex powder. The reasons leading to the above results were also discussed.

Luminescence characteristics of europium and terbium complexes with 1,10-phenanthroline in-situ synthesized in a silica matrix by a two-step sol-gel process

In-situ synthesis of europium and terbium complexes with 1,10-phenanthroline (phen) in silica matrix by a two-step sol-gel process has been proposed. The formation of europium and terbium complexes with phen in sol-gel derived silica gel were confirmed by the luminescence excitation spectra. The silica gels that contain in-situ synthesized europium and terbium complex exhibit the characteristic emission bands of the rare earth ions. Furthermore. the rare earth ions present longer fluorescence lifetimes than the comparable pure complex powder and the complexes dissolved in ethanol solutions. The luminescence properties of the silica gels codoped with europium (or terbium) and phen were also investigated with respect to the gels doped with europium (or terbium). (C) 1999 Elsevier Science B.V. All rights reserved.

Investigation of ergosterol in situ circular dichroic spectroelectrochemistry

In the present paper, the electrochemical behavior of ergosterol has been investigated by in situ circular dichroism (CD) spectroelectrochemistry with long path-length thin layer cell. E-0 (1.02V), alpha n(alpha) (0.302) of the electroxidation process of ergosterol were obtained from the CD spectroelectrochemical data. The mechanism of the electroxidation process of ergosterol is suggested.

In-situ synthesis of terbium complex with salicylic acid in silica matrix by a two-step sol-gel process

A process for in situ synthesis of terbium complex with salicylic acid by a two-step sol-gel method in silica matrix has been proposed. The luminescence properties of the silica gels codoped with terbium and salicylic acid have also been discussed with respect to that of the gel doped with terbium and that of pure terbium complex with salicylic acid.

In-situ microscopic FTIR spectroelectrochemical study of the reduction of K3Fe(CN)(6) in polymer electrolyte

Cyclic voltammetry and in-situ microscopic FTIR spectroelectrochemistry were used for the electrochemical and vibrational characterizations of the reduction process of K3Fe (CN)(6) in polyethylene glycol(PEG) with LiClO4 as supporting electrolyte at a Pt microelectrode. The rate of electron transfer is a function of the concentration of the supporting electrolyte. The redox potentials and cyclic voltammetric currents vary with Li/O molar ratio. The bl-situ spectroelectrochemistry shows that the infrared spectra are influenced by the concentration of LiClO4. The bridging cyanide groups with a structure Fe-I-C drop N ... Fe-I-C drop N are formed during the reduction process of K3Fe (CN)(6). There may be an activated complex between the Lif cation and the complex anion.

In situ microscopic FTIR spectroelectrochemistry study of oxidation of L-ascorbic acid in polymer electrolyte (PEG/LiClO4)

In situ microscopic FTIR spectroelectrochemistry behavior of L-ascorbic acid (H(2)A) in polymer electrolyte is reported for the first time. H(2)A undergoes a two-step oxidation, The oxidation waves shift towards more anodic potential values when the scan rate increases. The peak currents of the oxidation waves are proportional to the square roots of scan rate up to 100 mV/s, The in situ infrared spectra suggest that the product of the oxidation be dehydroascorbic acid, which may exist as a dimer.

In situ FTIR spectroelectrochemistry of a microarray electrode

A thin-layer microdisk array electrode (TLMDAE) was designed for in situ reflectance FTIR spectroelectrochemical studies. A theoretical estimation, cyclic voltammetry, chronoamperometry and in situ IR measurements demonstrate that this novel design of array electrode results in advantages such as reduced ohmic potential drop, small cell constant and facility for diffusional exchange between thin layer and bulk solution. It has been suggested that the enhanced edge diffusion on the TLMDAE leads to a reduced accumulation of species in the thin layer. (C) 1997 Elsevier Science S.A.

Rapid automated in-situ monitoring of total dissolved iron and total dissolved manganese in underground water by reverse-flow injection with chemiluminescence detection during the process of water treatment

Measurement of iron and manganese is very important in evaluating the quality of natural waters. We have constructed an automated Fe(II), total dissolved iron(TDI), Mn(II), and total dissolved manganese(TDM) analysis system for the quality control of underground drinking water by reverse flow injection analysis and chemiluminescence detection(rFIA-CL), The method is based on the measurement of the metal-catalyzed light emission from luminol oxidation by potassium periodate. The typical signal is a narrow peak, in which the height is proportional to light emitted and hence to the concentration of metal ions. The detection limits were 3 x 10(-6) mu g ml(-1) for Fe(II) and the linear range extents up to 1.0 x 10(-4) and 5 x 10(-6) mu g ml(-1) for Mn(II) cover a linear range to 1.0 x 10(-4) mu g ml(-1). This method was used for automated in-situ monitoring of total dissolved iron and total dissolved in underground water during water treatment. (C) 1997 Elsevier Science B.V.

In-situ FTIR spectroelectrochemical investigation of cobalt(II)-cyanoferrate polymeric film coated on a glassy carbon electrode

Cobalt(II)-cyanoferrate polymeric film has been electrochemically deposited on a glassy carbon electrode and investigated by cyclic voltammetry and in-situ reflection FTIR spectroscopy. A reorientation of the terminal C=N groups upon redox reactions was proposed. The stretching vibration mode of the terminal C=N groups associated with Fe(III) was observed at 2122 cm(-1), however, the stretching vibration mode for terminal groups associated with Fe(II) did not appear. This process could result in a switch between lattice-closed and lattice-opened surface structure. (C) 1997 Elsevier Science B.V.