Cyclic Voltammetry Determination of Epinephrine with a Nano-gold Modified Glassy Carbon Electrode in the Presence of High Concentration Ascorbic Acid

Nano-gold (NG) modified glassy carbon electrodes (GCEs) were used for determination of epinephrine (EP) in the presence of high concentration ascorbic acid (AA) by cyclic voltammetry (CV). This modified electrode can not only catalytically oxidize EP and AA, but also separate the catalytic peak potentials of EP and AA by about 183.5 mV. In pH = 7.0 ogisogate byffer solution, the linear range of epinephrine was 5 106 ~ 1 ?10-4 mol/L.

Preparation and Electrochemical Application of Praseodymium Modified TiO2-NTs/SnO2-Sb Anode by Cyclic Voltammetry Method

A Pr-doped TiO2-NTs/SnO2-Sb electrode was prepared by a simple method, cyclic voltarnmetry （CV）. The methyl orange （MO）aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO2-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseo- dymium oxide was successfully doped into the SnOz-Sb film by CV method. Due to the doped Pr, the oxygen evo- lution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The Ct/C0（φ） was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.099 3 min-1. The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.

Determination of Metamizole Sodium by Cyclic Voltammetry Under Microwave Activation

Microwave radiation was applied to the detection of metamizole sodium by cyclic voltammetry. The electrochemical characteristics of metamizole sodium were studied by cyclic voltammetry at GC electrode under microwave radiation and a considerable current enhancement was observed for metamizole sodium in aqueous 0.05 mol/L H2SO4. Under the optional conditions, metamizole sodium was determined in the absence and presence of microwave activation. In the absence of microwave activation cyclic voltammogram of metamizole sodium shows good linear relationship in a concentration range of 8.0×10^-5-1.0×10^-3 mol/L in aqueous 0.05 mol/L H2SO4 with a detection limit of 6.75× 10^-6 mol/L（S/N=3） and the equation of linear regression is Ip=12.973c-0.1905（R^2=0.9996, n=6）; in the presence of 80 W microwave activation cyclic voltammogram of metamizole sodiumin shows good linear relationship in a concentration range of 4.0× 10^-5-1.0×10^-3 mol/L in aqueous 0.05 mol/L H2SO4 with a detection limit of 4,41 × 10^-6 mol/L（S/N=3） and the equation of linear regression is Ip=25.107c-0.1193（R^2=0.9973, n=7）. The current in the presence of 80 W microwave activation increases to about 2 orders of magnitude compared with that in the absence of microwave activation. The proposed method in the presence of microwave activation showed high selectivity and sensitivity, and the sampling of the disposal method is simple. The method was verified by the determination of Metamizole Sodium tablet with satisfactory results.

Assessment of Defects and Collapsed Sites in Self-Assembled Alkanethiol Monolayer on Gold by Cyclic Voltammetry and A.C.Impedance

Self-assembly of octadecyl mercaptan on gold was investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy (EIS). Results of CV experiments show thatthere are no structUral defects exposed directly to the redox couple in solution, but EISexperiments indicate that collapsed sites exist in the monolayer. A method to estimate the degree ofdisorder in the Au/thiol monolayer surface is proposed by using admittance plane plot.

Studies on the Nucleophilicity and Scavenge of Superoxide Ion by Cyclic Voltammetry

Superoxide ion was generated by the electrochemical reduction of oxygen at a platinum electrode in dimethylsulphoxide (DMSO). This work was focused on the nucleophilicity and scavenge of electrogenerated\|superoxide ion by cyclic voltammetry. The nucleophilic displacement reactions of superoxide ion with ethyl acetate and diethyl adipate were discussed and the reason for remarkable influence of diethyl adipate was elucidated. The scavenging activity of ascorbic acid was evaluated and the result allowed the conclusion that the scavenging ability of ascorbic acid is much lower in DMSO than in aqueous phase. UV\|spectrum of electrogenerated superoxide ion in DMSO exhibited a single absorption band with λ max at 275 nm, which certified further that the method of electrogeneration was reliable and superoxide ion was stable in DMSO.

Preparation and Cyclic Voltammetry Characterization Of Cu-dipyridyl Imprinted Polymer

Polymer capable of specific binding to Cu-dipyridyl complex was prepared by molecular imprinting technology. The binding specificity of the polymer to the template (Cu-dipyridyl complex) was investigated by cyclic voltametric scanning using the carbon paste electrode modified by polymer particles in phosphate buffer solution. Factors that influence rebinding of the imprinted polymer were explored. The result demonstrated that the cyclic voltammetry was an efficient approach to explore interactions between template and imprinted polymers.

Ultrafast cyclic voltammetry with asymmetrical potential scan

Based on the perfect ohmic drop compensation by online electronic positive feedback, ultrafast cyclic voltammetry with asymmetrical potential scan is achieved for the first time, with the reduction of anthracene acting as the test system. Compared with the traditional cyclic voltammetry utilizing symmetrical triangular waveform as the excitation one, the new method allows a simpler approach to mechanistic analysis of ultrafast chemical reactions coupled with a charge transfer. And perhaps more important, it also provides a way to eliminate the interference of the adsorbed product in dynamic monitoring. 2007 Zhi Yong Guo. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

A COMPARISON OF THE DETERMINATION OF STABILITY CONSTANTS OF COMPLEXES OF Cd(Ⅱ)WITH AMINO ACIDS AND SIMPLE PEPTIDES USING MICRO—pH—METRIC TITRATIONS AND CYCLIC VOLTAMMETRY

This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly, Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra- tions and the application of convolution—deconvolution cyclic voltammetry at 25℃ and I=0.10 mol· dm^(-3)(KNO_3).Stability constants were calculated from pH—metric data using the SUPERQUAD com- puter program and cyclic voltammograms were collected,stored and manipulated using the EG and G CONDECON 300 software.A considerably larger ligand:metal ratio(e,g.50:1)was possible using voltammetry.Evaluation of results from the two techniques suggests that stability constants for the species[CdL_2]and[CdL_3]are reliable when calculated fromvoltammetry while those for[CdL]are more reliable when determined by pH-metric titration.

Evaluating the Stability of Active Manganese Sites During Electrochemical Reactions by Cyclic Voltammetry

Manganese oxides are a promising class of electrocatalysts for renewable energy devices,such as fuel cells.Mn(Ⅲ) ions with e_(g) electron filling of-1 are the active sites for manganese-based electrocatalysts.However,Mn(Ⅲ) sites may be disproportionated during electrochemical reactions,thus reducing the number of Mn(Ⅲ) active sites and decreasing the catalytic activity of manganese oxides.In this work,we developed a facile cyclic voltammetry method to monitor the evolution of Mn(Ⅲ) sites on a series of manganese oxides under "working" conditions.We proposed a descriptor S_(Mn(Ⅲ)) to describe the stability of Mn(Ⅲ).Our simulated and experimental results show that the higher is S_(Mn(Ⅲ)),the higher the active Mn(Ⅲ)density,and the higher the electrocatalytic activity of the manganese oxide electrocatalyst.

Analysis of Bacterial Cellulose/Ionic Liquid MWCNTs via Cyclic Voltammetry

Cyclic voltammetry based on an electrochemical technique is one of the current methods that measure the developments of the electrochemical properties in biomaterial samples under conditions. Biomaterial structure was changed by conductive material while these materials caused a connective network in whole of them and was able to transfer electrons inside of biomaterials. These changes in physical and chemical properties are investigated by analysis tools such as cyclic voltammetry (CV), X-radiation (XRF) and Ultraviolet-visible spectroscopy (UV-Vis). Bacterial cellulose is biodegradable, biosynthesis of A. xylinum which is a three-dimensional nano-network structure with a distinct tunnel and pore structure. In this study, the composite process produced electrically conducting bacterial cellulose pellicles containing well-dispersed and embedded multi-walled carbon nanotubes (MWCNTs) Ionic liquids (ILs), as observed in cyclic voltammetry (CV). For this purpose, we used a special tool, called OriginLab which is an industry-leading scientific graphing and data analysis software. The cyclic voltammetry graph presents the behavior of this composite which consists of a relationship between CNT dispersion, conductivity rate and changes in bacterial cellulose structure. The electrical conductivity of the cellulose/MWCNT composite was found different with respect to CNT dispersion. It was found that the incorporation process was a useful method not only for dispersing MWCNTs-ILs in an ultrafine fibrous network structure, but also for enhancing the electrical conductivity of the polymeric membranes.

Interaction between Eu-phenylalanine and DNA Using Cyclic Voltammetry and UV Spectroscopy

The interaction between DNA and the Eu(Phe) 3+ 3 complex ion has been studied by means of cyclic voltammetry and differential UV spectroscopy The results depicted an obvious decrease of peak current in CV plot after the reaction between the two species studied The observed peak potential separation was increased but the diffusion coefficient of Eu complex ion was decreased Hypochromicity was observed at 226 and 258 nm after the predicted interaction of them A preliminary interpretation is proposed for discussion

Imprinted Polymeric Film-Based Sensor for the Detection of Dopamine Using Cyclic Voltammetry

The imprinted polymeric film was synthesized on the glass-carbon electrodes directly. The response to the template molecule-dopamine and other molecules with similar structure was measured by cyclic voltammetry. The response of dopamine on imprinted electrode was much higher than that of other molecules, because of the existing of micro-cavities in polymeric film fitting with the size and shape of dopamine in the imprinted polymer. Experimental results showed that dopamine can be enriched by the imprinted film, therefore increasing the sensitivity of the sensor. The imprinted film could also efface the interference of ascorbic acid, indicating that dopamine can be determined with a large excess of ascorbic acid.

Study on Mechanism of Electrodeposition of Y(Ⅲ) in Molten LiF-YF_3-Y_2O_3 by Cyclic Voltammetry

The mechanism of the cathodic process of Y(Ⅲ) on platinum and molybdenum electrode in molten LiF YF 3 Y 2O 3 was investigated by means of cyclic voltammetry. The number of electron transferred was calculated. The results show that the electrochemical reduction of Y(Ⅲ) is a reversible one step three electrons reaction and the cathodic process is diffusion controlled. The reductive product easily forms the intermetallic compounds with the platinum electrode, but it is pure yttrium on the molybdenum electrode.

Reaction between tetravalent cerium ion and chloride ion and effect of thiourea using cyclic voltammetry

To monitor the reaction between Ce^(4+) ion and Cl-ion at the electron level,an electrochemical experiment was designed in this work.Herein,the intermediate and final products that may be produced during the redox reaction are directly tracked by using cyclic voltammetry,and the influences of Ce^(4+) ion concentration,temperatu re and F-ion on the reduction peak potential of Ce^(4+) ion were investigated.The results show that Ce^(4+) ion reacts with Cl-ion through an irreversible reaction without any intermediate products,and the rate-determining step of the reaction is diffusion during the electrode reaction.The effects of temperature(20-40℃) and Ce^(4+) ion concentration(0.04-0.12 mol/L) on the reduction peak pote ntial of Ce^(4+) ion can be ignored,but the higher the molar ratio of F-to Ce^(4+)(0-3 mol/mol),the mo re easily the reduction of Ce^(4+) ion to Ce^(3+) ion occurs.Additionally,the Ce^(4+) ions are preferentially reduced by thiourea when thiourea is added in the HCl solution,and thiourea inhibits the oxidation of Cl-ions to Cl_(2) by forming a complex with Cl-ions.This work provides a theoretical basis for the role of thiourea in inhibiting Cl_(2) production and offers a new way to find new reductants.

Significant capacitance enhancement induced by cyclic voltammetry in pine needle-like Ni-Co-Cu multicomponent electrode

Poor conductivity and rate capability are the obstacles faced by nickel-cobalt composites as electrode materials for supercapacitor application.Herein,simple electrochemical treatment conducted by cyclic voltammetry is applied and the overall performance of the active material is considerably enhanced.We discover that this treatment triggers the formation of Ni-Co-Cu ternary composite and optimizes the crystal structure of the untreated counterpart.The areal capacitance of the treated sample rockets up to 6.13 F cm^(-2)at 2 m A cm^(-2),almost 13 times higher than the untreated ones.Besides,the resistance is substantially reduced by cyclic voltammetry treatment.Moreover,the Coulombic efficiency and stability are concurrently elevated.The reasons behind this treatment are mulled over and reasonable hypothesis is suggested.This study provides a cheap and effortless way to reform the structures of as-obtained samples as well as vigorously raise the performance of current available materials.

Theory and application of cyclic voltammetry for measurement of fast electrode kinetics at microdisk electrode

An analytical expression describing voltammetric behaviors responses at microdisk electrode for various diffusion conditions and degrees of reversibility is reported in this paper. Results of theoretical calculation made it possible to use cyclic voltammetry to evaluate heterogeneous rate constants under intermediate diffusion conditions. At relatively low scan rate, the distortion of current-voltage can be reduced due to small iR drops and charging current. The effects of transfer coefficient, alpha, kinetic parameter, lambda(=k(0)r/4D), and switching potential, xi(8), on potential peak separation are discussed in detail. The relationship obtained in this paper between potential peak separation and lambda is in good agreement with that in Ref. 14, whose authors have got their results by using digital simulation technique. After the experiment of Fe(CN)(6)(4-) oxidation, k(0) and alpha were obtained by the theory of this paper. The result agrees with that in Ref. 19.

Study on surface acid-base property of carboxylic acid-terminated self-assembled monolayers by cyclic voltammetry and electrochemical impedance spectroscopy

Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the surface acid-base property of carboxylic acid-terminated self-assembled monolayers (SAMs). A carboxylic acid-terminated thiol, such as thioctic acid (l,2-dithiolane-3-pentanoic acid), was self-assembled on gold electrodes. Electron transfer between the bulk solution and the SAM modified electrode was studied at different pH using Fe(CN)63? as a probe. The surface pKa. of thioctic acid was determined by cyclic voltammetry and electrochemical impedance spectroscopy to be 5.6 ± 0.1 and 5.8 ± 0.1, respectively. The method is compared with other methods of monolayer pKa measurement.

A comparison of the determination of stability constants of complexes of Pb(II) with amino acids using micro-pH-metric titrations and cyclic voltammetry

This paper reports the determination of stability constants for complexes of Pb(Ⅱ) with Gly, Ala, Asp and Gly-Gly using both micro-pH-metric titrations and the application of convolution-de- convolution cyclic voltammetry at 25℃ and I = 0.10 mol.dm^(-3)(KNO_3). Stability constants were calculated from pH-metric data using the SUPERQUAD computer program and cyclic voltammograms were collected, stored and manipulated using the E G and G CONDECON 300 software. A consider- ably larger ligand: metal ratio (e.g. 50:1) was possible using voltammetry. Under these conditions, hydroxy complex formation was minimised and the formation of bis-complexes optimised. Computer based calculations were carried out on PC-compatible microcomputers fitted with mathematics co- processors. Evaluation of results from the two techniques suggests that stability constants for the species [PbL_2] are reliable when calculated from voltammetry while those for [PbL] are mote reliable when determined by pH-metric titration.

Electrochemical behavior and cyclic fading mechanism of LiNi_(0.5) Mn_(0.5) O_2 electrode in LiNO_3 electrolyte

Electrochemical behavior of layered LiNi0.5Mn0.5O2 in LiNO3 aqueous solution and its cyclic fading mechanism in electrolytes with different pH values were investigated. CV results show that LiNi0.5Mn0.5O2 has good electrochemical reversible behaviors in 5 mol/L LiNO3 solution. Meanwhile, the electrode in 5 mol/L LiNO3 with pH value of 12 demonstrates the best electrochemical stability. Based on the electrochemical impedance spectroscopy （EIS）, X-ray diffraction （XRD） and scanning electron microscopy （SEM） results, it is proposed that suppressed charge-transfer resistance is the major reason, which is probably ascribed to the more stable electrode surface and less structure change.