bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of the medium on the polarographic behavior of Cu(II)
Authors: Lurdes S. M. , Gonçalves Sim˜Es , Sigg Laura 
Published: May 2005

AbstractThe critical evaluation of the determination of copper, by pulse and stripping voltammetric methods in the presence of ligands occurring in natural waters was performed. The conditions under which Cu(I) can be detected, either due to its presence in solution or as an electrochemical intermediate, were investigated. The ligands Cl− and NH3 were considered and their effects in analytical determinations of Cu in natural waters are discussed. Concentrations of Cl− > 1.6 × 10−2 M and NH3 > 10−3 M lead to the reduction of Cu( II) in two steps with Cu(I) intermediates. We illustrate that the stability constants of complexes of Cu(I) can be determined by starting with the more stable solutions of copper(II) and electrochemically (in situ) producing Cu(I).
Determination of transition metals in natural waters by microprocessor‐controlled voltammetry in comparison with zeeman graphite furnace atomic absorption spectrometry
Authors: Buldini Pier Luigi , Ferri Donatella , Nobili Dario 
Published: May 2005

AbstractInformation on the transition metals content in natural waters is of great environmental interest. The procedures presented in this paper deal with the simultaneous determination of copper, cadmium, lead, and zinc in 0.05 M nitric acid (0.05 M HNO3 + 0.1 M CTRAc) 0.1 M citric acid by differential pulse anodic stripping voltammetry or differential pulse polarography; manganese, nickel, and cobalt were determined in ammonia/ammonium acetate buffer at pH 9.1 by differential pulse anodic or cathodic stripping voltammetry, titanium and relevant iron concentrations by pulse polarography in 0.2 M oxalic acid in the presence of 0.1 M potassium chlorate. The voltammetric schemes and response are critically compared to Zeeman graphite furnace atomic absorption spectrometry.
Potentiometric study of the nucleation of Cu2O after its formation from fehling solutions and reducing sugars
Authors: Nanos Christos G. , Konidari Constantina N. , Karayannis Miltiades I. 
Published: May 2005

AbstractThe oxidation of glucose by Fehling solution was followed by various solid‐state ion‐selective electrode. The shape of the recorded potential vs. time transient curves at three different electrodes (Cu2 + Ph2+, and Ag+/S2−) was explained on the basis of the known mechanisms of formation of precipitates, the growth of crystals, and adsorption/desorption phenomena. The curves are peculiar in shape, are very reproducible, and show three distinct parts. The potential changes of the electrodes are due to the consumption of OH− during the reaction, as well as to its adsorption and desorption on the Cu2O precipitate. The effects on the values of different curve parameters of the concentrations of glucose, OH−, and K, Na‐tartrate, as well as the temperature, were studied.
The wall‐jet ring‐disc electrode: The measurement of homogeneous rate constants from steady state ring currents
Authors: Brett Christopher M. A. , Oliveira Brett Ana Maria C. F. , Compton Richard G. , Fisher Adrian C. , Tyley Gwynfor P. 
Published: May 2005

AbstractThe wall‐jet ring‐disc electrode is shown to provide a convenient means determining homogeneous rate constants by means of ring current measurements as a function of disc currents and electrolyte flow rates. Theory is provided for the analysis of such “collection efficiency” experiments and applied to the specific case of the bromination of anisole, where good agreement with experiment is found. Advantages with respect to the rotating ring‐disc electrode are pointed out.
Enzyme electrodes for ADP/ATP with enhanced sensitivity due to chemical amplification and intermediate accumulation
Authors: Yang Xiurong , Johansson Gillis , Pfeiffer Dorothea , Scheller Frieder 
Published: May 2005

AbstractSubstrate recycling is used for making a highly sensitive enzyme electrode for the determination of ADP/ATP. A graphite electrode is modified with an adsorbed bis(benzophenoxazinyl) derivative of terephthaloic acid and covered with a gel containing entrapped glucose‐6‐phosphate dehydrogenase, pyruvate kinase, and hexokinase, all behind a dialysis membrane. The recycling produces NADH, which is detected by oxidation at the modified electrode. The cycle is driven by conversion of phosphoenolpyruvate to pyruvate and by phosphorylation of glucose to glucose‐6‐phosphate, which is oxidized to the corresponding gluconic acid with the simultaneous production of NADH. The calibration curves for ADP and ATP were linear to about 0.4 μM and the detection limit was 1 nM. A steady‐state response was obtained after 2–10 min. Sensitivity toward ADP can be increased further by the accumulation of ATP inside the membrane.
The effect of anodic surface treatment on the oxidation of catechols at ultrasmall carbon ring electrodes
Authors: Fishman Harvey A. , Ewing Andrew G. 
Published: May 2005

AbstractElectrochemical anodic treatment at ultrasmall carbon ring electrodes appears to result in the formation of an oxide film that displays charge‐selective and pH‐dependent enhancements following treatment. Voltammetry after treatment in pH 7.4 citrate‐phosphate buffer is more Nernstian for dopamine (DA) and less Nernstian for 3,4‐dihydroxyphenylacetic acid (DOPAC). However, oxidation in pH 2.8 buffer gives rise to voltammetry that is less Nernstian for both DA and DOPAC. Extensive surface oxidation in potassium hydroxide apparently forms a thick layer that acts like a thin layer reservoir for adsorbed analyte. Voltammetry following extensive treatment is attenuated and peak shaped. Minimal surface oxidation in KOH results in more Nernstian sigmoidal voltammetry with only light current attenuation. The data suggest that an oxide layer formed following anodic treatment is non‐uniform and leaves sites of activated carbon exposed on the surface. Furthermore, it appears that this layer has cation‐exchange properties giving rise to charge transfer selectivity. A model of the surface formed following anodic oxidation is consistent with previous models involving both surface cleanliness and carbon structure orientation.
Determination of amalgam‐forming metals by anodic stripping voltammetry in solutions containing dissolved oxygen
Authors: Kopanica Miloslav , Stara Vera 
Published: May 2005

AbstractAmalgam‐forming metals can be determined by anodic stripping voltammetry in solutions containing dissolved oxygen. The procedure uses a modified mercury film electrode prepared by deposition of mercury on the surface of a silica‐gel/carbon composite electrode. Between determinations the film is removed from the electrode surface either mechanically or by a potential pulse. Lead was determined over the concentration range from 0.01 to 250 μM, with relative standard deviation values not exceeding ± 5%. The method was applied for the determination of metals in used motor oil.
Stripping voltammetry of uranium based on adsorptive accumulation of its 4‐(2‐pyridylazo) resorcinol complex at the static mercury drop electrode
Authors: Farias Pércio A. M. , Ohara Aniy K. 
Published: May 2005

AbstractA highly sensitive electrochemical stripping procedure for uranium is reported. Accumulation is achieved by controlled adsorption of the uranium/4‐(2‐pyridylazo) resorcinol complex on the static mercury drop electrode. The effect of various operational parameters on the stripping response is discussed. The detection limit is 0.2 nM with 10 min preconcentration. The response is linear over a 9.3 × 10−9−3.0 × 10−6 M concentration range, and the relative standard deviation (at the 24 μg·l−1 level) is 3%. Most cations and anions do not interfere in the determination of uranium; some interferences are eliminated by the addition of CDTA and EDTA. The applicability of the method to fresh water and seawater is demonstrated (the results obtained for uranium in reference seawater samples, NASS−2, were 2.95 μg·l−1 with standard deviations of 0.20 μg·l−1 (n = 5).
Correlation between the degree of activation by galvanostatic pretreatment and structure of biogenic amine compounds
Authors: Mattusch Jürgen , Werner Gerhard 
Published: May 2005

AbstractThe influence of steric and electronic effects of Biogenic compounds on their redox behavior at an electrochemically pretreated glassy carbon electrode in comparison to the polished electrode is elucidated by cyclic voltammetric data. The improvement of reversibility on a pretreated electrode increases mainly in order of carboxylic to amine substituent in position 1, acting by the I‐effect, and of unsymmetrical substituted compounds in positions 3 and 4, to symmetrical (dihydroxy‐) substituted compounds as attributed to steric hindrance of the electrode transfer.
Amalgam electrodes: Direct electrochemical generation of cadmium macrocyclic complexes
Authors: Boudon C. , Gisselbrecht J. P. , Gross M. 
Published: May 2005

AbstractThe electrochemical oxidation of cadmium amalgam was studied in the nonaqueous solvents CH2Cl2, 1,2‐C2H4Cl2 and propylene carbonate. Significant coordination effects were observed between the electrogenerated Cd(II) ions and 18‐membered macromonocyclic ligands, each containing six Lewis bases heteroatoms: 18‐O6, 18‐S6, 18‐N2O4, and 18‐N6. The stoichiometries and the stabilities of the resulting complexes were determined. These stabilities increase from 18‐O6 or 18‐S6 to 18‐N6.
Anodic stripping voltammetry at mercury “films” deposited on conducting poly(3‐methylthiophene) electrodes
Authors: Wang Zhi , Galal Ahmed , Zimmer Hans , Mark Harry B. 
Published: May 2005

AbstractThe incorporation of mercury into a conducting poly(3‐methylthiophene) [P3MT] film results in an effective electrode for the analysis of lead in aqueous media. Mercury “films” were deposited electrochemically following the electropolymerization step. The resulting surfaces were characterized by cyclic voltammetry, scanning electron microscopy, and X‐ray analysis techniques. The analytical performance of the electrode was examined for the determination of lead (II) ions in aqueous media. The differential pulse peak current, at −0.59 V, is ca 10‐fold larger than the corresponding peak at the plain platinum electrode. Linear calibration curves are obtained for lead concentrations ranging from 0.1 to 0.8 ppm. The detection limit is 0.05 ppm. The relative standard deviation (at the 0.3 ppm level) is 2%. Interference effects were also studied. The new polymer modified electrode showed great promise toward resistance to surfactant fouling.
A new polymeric mercury thin‐film electrode
Authors: Wallace G. G. , Imisides M. D. 
Published: May 2005

AbstractA chemically modified mercury thin‐film electrode (MTFE) is presented that employs an electrochemically generated nonconducting polymer (poly‐N‐ethyltyramine), which has been derivatized with surface dithiocarbamate groups. Mercury is deposited chemically onto the electrode by complexation and, following electrochemical reduction of the mercury, is used as a substrate for anodic stripping voltammetry (ASV) of cadmium, lead, and copper. The properties of a conventional MTFE are compared with the modified electrode.
Determination of organochlorine pesticides by polarography in emulsified medium
Authors: Reviejo A. Julio , Samprón Arturo , Pingarrón José M. , Polo Luis M. 
Published: May 2005

AbstractA polarographic study of the organochlorine pesticides dieldrin, heptachlor, endosulfan, and endosulfan sulfate in an emulsified medium formed with ethyl acetate and a mixture of two surfactants, Hyamine 2389 and Triton X‐405, as emulsifying agent, is reported. Well‐defined peaks were obtained by differential pulse polarography (dpp). Neither preceding acid‐base equilibria nor mechanism changes are involved in the reduction processes. The characteristics of the electrode processes were examined at pH 8.0 for heptachlor and at pH 6.0 for the other pesticides. The diffusion coefficients were calculated as well as the kinetic parameters αna and k. The mechanisms of the polarographic reduction processes are proposed and the different behavior of heptachlor is discussed. Linear calibration plots were obtained using dpp over different concentration ranges; the analytical characteristics of the methods were determined. The effect of the presence of the other pesticides on the ip and Ep values of each one of the four pesticides was studied. Simultaneous determination of heptachlor and endosulfan sulfate was possible.
Pulsed electrochemical detection at noble metal electrodes in liquid chromatography
Authors: Johnson Dennis C. , LaCourse William R. 
Published: May 2005

AbstractThe direct electrochemical detection of numerous polar aliphatic compounds is achieved at Au and Pt electrodes under the control of multistep potential‐time waveforms. In this technique, called “Pulsed Electrochemical Detection (PED),” the waveforms manage the sequential processes of sampling the faradaic signal, from the oxidation of analyte, followed by oxidative cleaning and reductive reactivation of the electrode surfaces. The response mechanisms in PED are strongly influenced by surface properties of the electrodes and, therefore, members of each chemical classification detected are observed to produce virtually identical voltammetric response. Consequently, applications of PED have their greatest analytical significance when coupled with Liquid Chromatography (LC) to achieve a priori resolution of complex mixtures. The basic concepts of PED are reviewed and LC‐PED results are presented for a variety of samples containing mixtures of alcohols, carbohydrates, alkanolamines, amines, and sulfur compounds.
A solid polymer electrolyte amperometric detector for FIA and HPLC with mobile phases of low conductivity
Authors: Loub Lukáš , Opekar František , Pacáková Věra , Štulík Karel 
Published: May 2005

AbstractAn amperometric cell with a small platinum wire working electrode, a submicroliter geometric volume, and a solid polymer electrolyte (Nafion) was constructed and tested. The cell permits sensitive and reliable detection even in mobile phases of negligible electric conductivity, (e.g., distilled water or nonpolar organic solvents). The sensitivity is substantially higher than that attained with similar cells containing large‐are working electrodes; typical limits of detection amount to analyte concentrations between 10−7 and 10−6 mol/dm3, corresponding to subnanogram amounts in common HPLC sample volumes. The detector response exhibits satisfactory linearity, a linear dynamic range of at least three concentration decades, and a good precision, with relative standard deviations of 1 to 5%. This cell substantially widens the possibilities of amperometric detection, permitting direct application, for example, to normal‐phase HPLC or to methods with programmed composition of the mobile phase (gradient elution).
Electrocatalytic oxidation and flow detection of hydrazine compounds in liquid chromatography at a vitamin B‐12 adsorbed glassy carbon electrode
Authors: Zhou Jianxun , Wang Erkang 
Published: May 2005

AbstractA vitamin B‐12 chemically modified electrode (CME) was constructed by adsorption of vitamin B‐12 onto a glassy carbon surface. The electrode catalyzes the electrooxidation of hydrazine compounds over a wide pH range. The electrocatalytic behavior of hydrazines is elucidated with respect to the CME preparation conditions, solution pH, operating potential, mobile phase flow rate, and other variables. When applied to liquid chromatographic detection of the analytes, the vitamin B‐12 CME yielded a linear response range over 2 orders of magnitude, and detection limits at the picomole level. The vitamin B‐12 CME offers acceptable catalytic stability in both batch and flow systems.
Cross correlation with digital techniques in flow injection analysis and high performance liquid chromatography
Authors: Curran D. J. , McKeans R. E. 
Published: May 2005

AbstractDigital techniques are implemented to demonstrate the use of cross correlation to improve the signal‐to‐noise ratio for measurements involving analog detectors in flowing stream analysis methods. Two examples are presented. The first involves amperometric detection of dopamine using flow injection analysis. The reference and analyte signals are digitized and cross correlation performed by software using the fast Fourier transform (FFT). The second example is the determination of a mixture of catecholamines by HPLC using a UV detector. Multiplication of the digitized reference and analyte signals was carried out in the time domain followed by low pass filtering. Improvement in the signal‐to‐noise ratio up to a factor of 35 was found, depending on the compound.
Cathodic behavior of 4,5‐dimethoxy‐2‐nitroamphetamine
Authors: Squella J. A. , Pezzani M. , Cassels Bruce K. , Aillon‐Torres Milton , Rezende Marcos C. , Nuñez‐Vergara L. J. 
Published: May 2005

AbstractThe amphetamine derivative 4,5‐dimethoxy‐2‐nitrophenyl‐2‐aminopropane, a positional isomer of the potent hallucinogen DON, was studied by cyclic voltammetry and polarography. The nitro compound was reduced to the corresponding hydroxylamine under the experimental conditions used.
Simultaneous polarographic determination of ascorbic acid and dipyrone in pharmaceutical preparations
Authors: Belal F. 
Published: May 2005

AbstractA polarographic method is described for the simultaneous determination of ascorbic acid and dipyrone in dosage forms. The method is based on the anodic polarographic waves produced by both compounds in Walpole acetate buffer (pH 3.6). The separation of the two waves (>0.65 V) is sufficient to allow accurate measurements. The proposed method was successfully applied to the analysis of commercially available ampules, and the results obtained were of satisfactory accuracy and precision.
Electrochemical reduction of nitrofurazone and its determination in pharmaceutical dosage forms by differential pulse polarography
Authors: Reday C. Suresh , Reddy S. Jayarama 
Published: May 2005

AbstractThe electrochemical reduction behavior of nitrofurazone has been studied by employing dc polarography, cyclic voltammetry, and differential pulse polarography in the universal buffers of pH ranging from 2.0 to 12.0. A differential pulse polarographic method is described for the determination of nitrofurazone in its pharmaceutical formulations using the standard addition method. The kinetic parameters, such as diffusion coefficients (D) and heterogeneous forward rate constant (k) values are evaluated using these techniques.
Adsorption of lead (II) on mercury electrodes from chloride‐bromide mixtures of high ionic strength
Authors: Zelić Marina , Branica Marko 
Published: May 2005

AbstractThe adsorption of lead (II) from chloride‐bromide mixtures of a high ionic strength (I=4 mol/L) to mercury electrodes was studied using square wave voltammetry, differential, and normal pulse polarography. The presence of excess chloride ions in the solution prevents additional surface complexation of PbBr2 with previously adsorbed free bromide ions and the formation of PbBr3− at the mercury drop. Adsorption effects are highly pronounced, even when PbBr2o makes less than 1% of dissolved metal, indicating that a mixed‐ligand species could be attached to the electrode. It is possible to explain nearly all experimental results by the surface activity of both PbBr2o and a mixed‐ligand complex PbBr2Cl.
Isopolymolybdic acid‐poly(4‐vinyl)pyridine film modified electrode
Authors: Dong Shaojun , Song Fayi , Wang Baoxing , Liu Baifeng 
Published: May 2005

AbstractElectrochemical polymerization of 4‐vinylpyridine produced a uniform poly(4‐vinyl)pyridine(PVP) film on the glassy carbon (GC) electrode surface. The isopolymolybdic acid‐PVP film‐modified electrode was prepared by soaking the PVP/GC electrode in the 0.05 M H2SO4 aqueous solution containing 0.005 M isopolymolybdic acid (H4Mo8O26). The latter (catalyst) is incorporated and held in the PVP film electrostatically. The electrochemical behavior and electrocatalytic properties of this H4Mo8O26–PVP/GC electrode was described. The results indicate that this modified electrode has good stability and electrocatalytic activity on the reduction of chlorate and bromate ions in aqueous solution. The catalytic process is regarded as an EC mechanism.
Anodic stripping voltammetry of selenium(IV) at a gold fiber working electrode
Authors: McLaughlin Kieran , Boyd Damien , Hua Chi , Smyth Malcolm R. 
Published: May 2005

AbstractThe anodic stripping voltammetry of selenium (IV) in a gold fiber electrochemical flow cell is described. The cell is simple to construct and flexible in its operation. The nonlinear diffusional mass transport characteristics of such small diameter electrodes influence the anodic stripping voltammetry of Se(IV) with the result that significant deposition of metal ions occurs during the scan period from the deposition potential to the peak potential. Therefore, an extremely short deposition period of the order of 20 seconds can be employed at the gold fiber electrode. The system described resulted in a linear working range from 0–15 ng/mL, a detection limit of 0.5 ng/mL Se(IV) and a relative standard deviation of 6% at 5 ng/mL (n = 7) in pure solution.
Electrochemical oxidation of 5‐hydroxytryptamine and 5‐hydroxyindoleacetic acid by integrated pulse linear scan voltammetry at ultrasmall gold ring electrodes
Authors: Lau Yau Yi , Wong Danny K. Y. , Luo Guoan , Ewing Andrew G. 
Published: May 2005

AbstractUltrasmall gold ring electrodes have been constructed by electrodeposition of gold onto carbon ring electrodes. Electrodes thus formed show similar adsorption/desorption peaks for oxygen in H2SO4 solution compared to those obtained at conventional‐sized electrodes. These electrodes have been used in conjunction with linear scan voltammetry and subsequent cleaning pulses to obtain repeatable quantitative results for the electochemical oxidation of 5‐hydroxytrptamine and 5‐hydroxyindoleacetic acid. This technique involves the use of a linearly scanned applied potential, followed by a large positive potential to clean the electrode oxidatively and negative potential for electrode activation. The result of the cleaning pulses is that oxidation products of 5‐hydroxytryptamine are cleaned off the electrode and reproducible voltammograms are obtained.
Stripping analysis on controlled‐growth mercury drop electrode
Authors: Kowalski Zygmunt , Migdalski Jan 
Published: May 2005

AbstractIn this study, special consideration is given to the “back‐diffusion effect” accompanying the process of electrochemical preconcentration and during the time between the end of this process and the initiation of stripping (that is, during the rest period). It is shown how far these effects can be eliminated when a Controlled‐Growth Mercury Drop Electrode (CGMDE), is applied. It has been demonstrated that controlled growth of the drop during preelectrolysis allows the formation of a homogeneous amalgamate of the deposited substances in the Hg drop and prevents the occurrence of the back‐diffusion effect. Quantitative relations between these factors and the back‐diffusion into the capillary thread of mercury are presented.