Analysis of Vitamin K_3 by a Fluorescent Spectroelectrochemistry Method

A simple and sensitive spectroelectrochemistry method for the determination of vitamin K3 was developed by combining electrolysis and fluoremetry. This method was based on that vitamin K3 was reduced at a glassy carbon electrode, and its product with characteristic fluorescence at 420 nm was determined with excitation wavelength at 309 nm. Under optimized electrochemical reaction conditions and fluorescent experiment parameters, the fluorescence intensity was proportional to the concentration of vitamin K3 in a range from 3.50×10^-7 to 1.05×10^-5 mol/L with a correlation coefficient of 0.9991, and detection limit was estimated to be 7.50× 10^-8 mol/L at a signal/noise ra- tio of 3. The relative standard deviation was less than 4.3%（n=5） and the recovery was in a range of 97%-105% for the determination of vitamin K3 in pharmaceutical preparations. The result is satisfactory for the determination of vitamin K3 as comparison to that from HPLC method.

IN-SITU REFLECTION MICROSCOPIC FTIR SPECTROELECTROCHEMISTRY AT MICRO-/ULTRAMICROELECTRODE

An in-situ reflection ultramicroelectrode microscopic FTIR spectroelectrochemical cell was constructed and demonstrated by using hexacyanoferrate redox couple in aqueous sulphate solution.An excellent microscopic SNIFTIRS reflection spectra had been obtained with no difficulty of IR beam focusing.The cell is simple in construction and convenient for use,And it will have most of all advantages of micro-/ultramicroelectrode.

Thin-layer Spectroelectrochemistry of 3,3′,5,5′-Tetramethyl-benzidine on Pt Minigrid Optically Transparent Electrode

The electrooxidation behavior of 3, 3′,5, 5′-tetramethylbenzidine(TMB) was investigated using a platinum minigrid optically transparent thin-layer spectroelectrochemical cell. TMB underwent one two-electron electrooxidation process to yield quinonediimine in the pH range from 2.0 to < 4.0, and two consecutive one-electron electrooxidation processes, gave the mediate product free radical of TMB first, then gave the oxidation product quinonediimine in the pH range from 4.0 to < 7.0. In the pH range from 7.0 to 10.0, the electrooxidation of TMB was also one two-electron electrooxidation process to yield an azo compound. The formal potential E0'and the electron transfer number of the electrooxidation of TMB at pH 2.0 and pH 8.4 were determined by spectroelectrochemical techniques.

Electrochemistry and In-situ Spectroelectrochemistry Studies of Carbazole and 9-Ethylcarbazole

Mechanisms of electron transfer of carbazole （CZ） and 9-ethylcarbazole （ECZ） were studied by electrochemistry and in-situ spectroelectrochemistry. The result indicated that the electrochemical reaction mechanism of ECZ was the same as that of CZ. Both of them undergo ECE process： the initial step is removal of one electron to generate very reactive cation radical, this species then proceeded by deprotonation-coupling reaction to form the corresponding dimer, which was oxidized continuously.

THE SENSITIVITY OF RESPONSE SIGNAL OF SPECTROELECTROCHEMISTRY(SEC)

In this paper, we propose the use of the molar absorbance/ potential ratio to measure quantitatively the sensitivity of response signal of SEC cell and the system under study. A simple equation was developed, and the major factors influencing the sensitivity were also assessed. The results obtained this way were in good agreement with actual cases.

A NOVEL OPTICALLY TRANSPARENT THIN LAYER ELECTRODE FOR IN SITU IR SPECTROELECTROCHEMISTRY

A novel design of IR OTTLE is shown to have sufficient sensitivity and experi- mental simplicity for obtaining IR spectra of the species generated during electrochemical oxidation-reduction.

THE STUDY OF PHARMACEUTICALS BY THIN-LAYER SPECTROELECTROCHEMISTRY(I)——THE REDOX MECHANISM OF NITROFURAZONE

The electrochemical behavior of nitrofurazone in dimethylformamide has been studied by cyclic voltammetry and in-situ thin-layer spectroelectrochemistry.The redox reactions are complicated at platinium electrode,and a possible electrochemical mechanism of nitrofurazone is proposed.

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.

Probing the redox process of p-benzoquinone in dimethyl sulphoxide by using fluorescence spectroelectrochemistry

Quinones are common organic compounds frequently used as model dissolved organic matters in water, and their redox properties are usually characterized by either electrochemical or spectroscopic methods separately. In this work, electrochemical methodology was combined with two fluorescence spectroelectrochemical techniques, cyclic voltafluorescence spectrometry （CVF） and derivative cyclic voltafluorescence spectrometry （DCVF）, to determine the electrochemical properties of p-benzoQuinone in dimethvl sulfoxide, an aprotic solution. The CVF results show that the electrochemical reduction ofp-benzoquinone resulted in the formation of radical anion and dianion, which exhibited a lower fluorescence intensity and red-shift of the emission spectra compared to that of p-benzoauinone. The fluorescence intensity was found to vary along with the electrochemical oxidation and reduction ofp-benzoquinone. The CVF and DCVF results were in good consistence. Thus, the combined method offers a powerful tool to investigate the electrochemical process of p-benzoquinone and other natural organic compounds.

Study on the Electrosynthesis of Coenzyme B_12 Model Compound by Spectroelectrochemistry

A lot of relevant work has been done on the important role of coenzyme B12 in various metabolism proceeding in biobody.Because the Co—C bond of coenzyme B12 and its models is instable, there are some difficulties in further studying

Piezoelectric transmission spectroelectrochemistry with a normal piezoelectric quartz crystal as an optically-transparent electrode

Piezoelectric transmission spectroelectrochemistry (PTSEC), i.e., the combination of electrochemistry and spectroelectrochemistry (SEC) with electrochemical quartz crystal microbalance (EQCM) technique is reported by using a normal piezoelectric quartz crystal (PQC) as an optically-transparent electrode (OTE). A theoretical relationship between the PQC response and the spectroelectrochemical response is derived and used to estimate the apparent molar absorptivity of the absorbing species deposited on the OTE on the PQC surface. The complex of copper with aspartic acid is used to test this new PQC-SEC technique. Results show that the combination of three such diverse techniques provides a very useful methodology for studying electrode processes and electrode surface characteristics in situ.

Study on the-Redox Process of Bilirubin and Biliverdin at Platinum Electrode by in Situ Spectroelectrochemistry

The electrochemical redox behavior of bilirubin(BR Ⅳ_α),biliverdin(BV Ⅳ_α)and their oxidized product bile-purpurin(Bi-Pu)have been studied by in situ spectroelectrochemical techniques,which reveals that the transformation of BR Ⅳ_α■BV Ⅳ_α■Bi-Pu can be achieved by controlling poten- tials.The kinetic investigation has shown that the heterogeneous electron transfer reactions of the couples of Ⅰ/Ⅱ and Ⅳ/Ⅲ were quasi-reversible and irreversible at a clean platinum electrode with the formal heteroge- neous electron transfer rate constants 1.5×10^(-4)cm·s^(-1)and 4.8×10^(-5)cm·s^(-1),respectively.

Simultaneous Raman and reflection UV/Vis absorption spectroelectrochemistry

In the present work,a new combination of Raman and ultraviolet and visible(UV/Vis)absorption spectroelectrochemistry in reflection mode is proposed.The new experimental setup allows obtaining the two kinds of spectroscopic data without interferences concomitantly with the electrochemical information.To the best of our knowledge,it is the first time to report the simultaneous obtention of electrochemical,electronic,and vibrational information in the same experiment.This new combination provides time-resolved information about the processes that are taking place on the electrode/solution interface which has significant implications in different fields of chemistry,such as modification of electrodes,studies of electrocatalytic reaction mechanisms,development of sensors,among others.Two different systems were used to demonstrate the advantages and capabilities of the brand-new technique,namely,the oxidation of potassium ferrocyanide,an out-sphere system that is usually employed in the validation of SEC techniques,and the electrochemical-surface enhanced Raman spectroscopy(EC-SERS)detection of crystal violet by in-situ formation of the silver SERS substrate,where the UV/Vis spectra were used to follow the formation of the SERS substrate,whereas the Raman response of a probe molecule was used to confirm either the formation of a nanostructured surface and to obtain the fingerprint of the molecule with a high time resolution.The brand-new experimental setup has shown to be useful,versatile,robust,compact,and easy to use for future applications.

ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE

The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0, respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus, the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here.

Progress of fundamental mechanism of formic acid decomposition and electrooxidation

Formic acid(HCOOH) is considered as a promising viable fuel-cell ingredient for low temperature proton-exchange membrane fuel cells as a consequence of their high safety and energy density. As one prototype reaction, the study of HCOOH decomposition and electrooxidation is also helpful to understand the reaction mechanism of other small molecular organics. Herein, we present a comprehensive overview of HCOOH decomposition and electrooxidation in different environment conditions and analyze the reaction mechanism from both experimental and theoretical point of view. Furthermore, we discuss the known strategies for improving the performance of HCOOH decomposition and electrooxidation catalysts. Finally, this review presents a prospect for the future study of HCOOH decomposition and electrooxidation.

Electrochemical and Spectroelectrochemical Studies on Electrooxidation Reactions of (TPP)Co~Ⅱ/NO_3^- System

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In-situ Microscopic FTIR Spectroelectrochemical Study of the Reduction of K_(3)Fe(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 K 3Fe(CN) 6 in polyethylene glycol(PEG) with LiClO 4 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 in situ spectroelectrochemistry shows that the infrared spectra are influenced by the concentration of LiClO 4. The bridging cyanide groups with a structure Fe Ⅱ—C≡N…Fe Ⅱ—C≡N are formed during the reduction process of K 3Fe(CN) 6. There may be an activated complex between the Li + cation and the complex anion.

In-situ Microscopic FT-IR Spectroelectrochemical Investigation of Polythiophene Film Modified Electrode

A polythiophene film was electrochemically deposited on a Pt micro plate electrode and investigated by cyclic voltammetry and in situ reflection microscopic FTIR spectroscopy. The FTIR analysis showed that the electropolymerization of thiophene on the Pt surface was affected by the surface adsorption processes of thiophene molecules. Two adsorption modes were identified. Two structure models of the polythiophene chain were observed simultaneously. It was proposed that the good conductibility of the polythiophene film was originated from a co vibratory equilibrium of the link part of model Ⅰ and model Ⅱ.

Spectroelectrochemical Studies on the Interactions of Complexes of Cu(phen)^(2+)_(2) and Cu(bpy)^(2+)_(2) with DNA

The interactions of the complexes of Cu(phen) 2+ 2 and Cu(bpy) 2+ 2 with DNA were investigated with electrochemistry and spectroelectrochemistry. Binding constants( K n + ) and the reaction model were obtained from their electrochemical behavior and electrochemical data. The binding constants( K 2+ ) for Cu(phen) 2+ 2 DNA and Cu(bpy) 2+ 2 DNA were 8 51×10 3 L·mol -1 and 3 27×10 3 L·mol -1 , and K +s were 3 09×10 4 L·mol -1 and 5 66×10 3 L·mol -1 respectively. The spectroscopic characteristics of the complexes of Cu(phen) 2+ 2 DNA and Cu(bpy) 2+ 2 DNA were studied in detail. Some significant spectroelectrochemical data were obtained. The interaction of DNA with complexes was described.