bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fourier Transformed Large Amplitude Square‐Wave Voltammetry as an Alternative to Impedance Spectroscopy: Evaluation of Resistance, Capacitance and Electrode Kinetic Effects via an Heuristic Approach
Authors: Sher Anna A. , Bond Alan M. , Gavaghan David J. , Gillow Kathryn , Duffy Noel W. , Guo Si‐Xuan , Zhang Jie 
Published: July 2005

AbstractA detailed simulation of Fourier transformed large amplitude square‐wave voltammetry is presented in the frequency domain for the process Red⇌Ox+e−. The simulation takes into account the influence of the electrode kinetics (Butler–Volmer model), uncompensated resistance (Ru) and double layer capacitance (Cdl). Of particular significance is the prediction that the even harmonic responses are only detected in the presence of quasi‐reversibility or uncompensated resistance, and also are essentially devoid of charging current. In contrast, the DC and odd harmonic AC components exhibit much larger faradaic currents and also contain charging current. Conveniently, detailed analysis of the simulated DC and AC harmonic components reveals the presence of readily recognised patterns of behaviour with unique levels of sensitivity to electrode kinetics,RuandCdl, that facilitate quantitative analysis of these terms. These electrochemical parameters are generally calculated by small amplitude impedance spectroscopy and utilisation of linear analysis of equivalent circuits. Experimental studies on the one electron oxidation of ferrocene in dichloromethane (0.1 M Bu4NPF6) and the one electron reduction of [Fe(CN)6]3−in aqueous 0.5 M KCl electrolyte analysed via heuristic forms of data analysis based on recognition of patterns of behaviour, are presented as examples of a reversible process with significant uncompensated resistance and a quasi‐reversible process with minimal ohmic drop, respectively. Results demonstrate the advantages of a more intuitively implemented form of data analysis than presently available with conventional forms of impedance spectroscopy.
Voltammetry of Dissolved Iron(III)–Nitrilotriacetate–Hydroxide System in Water Solution
Authors: Cuculić Vlado , Pižeta Ivanka , Branica Marko 
Published: July 2005

AbstractThe investigation of the dissolved iron(III)–nitrilotriacetate–hydroxide system in the water solution (I=0.1 mol L−1 in NaClO4; pH 8.0±0.1) using differential pulse cathodic voltammetry, cyclic voltammetry, and sampled direct current (DC) polarography, was carried out on a static mercury drop electrode (SMDE). The dissolved iron(III) ion concentrations varied from 2.68×10−6 to 6×10−4 mol L−1 and nitrilotriacetate concentrations were 1×10−4 and 5×10−4 mol L−1. By deconvoluting of the overlapped reduction voltammetric peaks using Fourier transformation, four relatively stable, dissolved iron(III) complex species were characterized, as follows: [Fe(NTA)2]3−, mixed ligand complexes [FeOHNTA]− and [Fe(OH)2NTA]2−, showing a one‐electron quasireversible reduction, and binuclear diiron(III) complex [NTAFeOFeNTA]2−, detected above 4×10−4 mol L−1 of the added iron(III) ions, showing a one‐electron irreversible reduction character. The calculations with the constants from the literature were done and compared with the potential shifts of the voltammetric peaks. Fitting was obtained by changing the following literature constants: log β2([Fe(NTA)2]3−) from 24 to 27.2, log β1([FeNTA]−) from 8.9 to 9.2, log β2([Fe(NTA)2]4−) from 11.89 to 15.7 and log β2([Fe(OH)2NTA]3−) from 15.63 to 19. The determination of the electrochemical parameters of the mixed ligand complex [FeOHNTA]−, such as: transfer coefficient (α), rate constant (ks) and formal potential (E°') was done using a sampled DC polarography, and found to be 0.46±0.05, 1.0±0.3×10−3 cm s−1, and −0.154±0.010 V, respectively. Although known previously in the literature, these four species have now for the first time been recorded simultaneously, i.e. proved to exist simultaneously under the given conditions.
Comparison of the Electrochemical Behavior of the High Molecular Mass Cadmium Proteins in Arabidopsis thaliana and in Vegetable Plants on Using Preparative Native Continuous Polyacrylamide Gel Electrophoresis (PNC‐PAGE)
Authors: Kastenholz Bernd 
Published: July 2005

AbstractIn Arabidopsis cytosol (supernatant) and in supernatants of vegetable plants high molecular mass cadmium proteins with molecular mass 200 kDa were isolated by using preparative native continuous polyacrylamide gel electrophoresis (PNC‐PAGE). Because of a different electrochemical behavior of the Cd proteins in Arabidopsis and endive supernatants on using the same PAGE method, it is concluded that the high molecular mass cadmium proteins of Arabidopsis and endive possess different isoelectric points. Consequently, different chemical structures of the Cd proteins with molecular mass 200 kDa are present in Arabidopsis thaliana and in endive. During the electrophoretic separation of vegetable metalloproteins by using the Model 491 Prep Cell from BioRad, electroanalytical processes like electrode reactions may play an important role.
Electrochemically‐Induced Deposition of Amine‐Functionalized Silica Films on Gold Electrodes and Application to Cu(II) Detection in (Hydro)Alcoholic Medium
Authors: Walcarius Alain , Sibottier Emilie 
Published: July 2005

AbstractWell‐adherent amine‐functionalized porous silica films have been deposited on gold electrodes by combining the self‐assembly technology, the sol–gel process, and the electrochemical modulation of pH at the electrode/solution interface. A partial self‐assembled monolayer of mercaptopropyl‐trimethoxysilane (MPTMS) was first formed on disposable gold electrodes from recordable CDs (Au‐CDtrodes). The so pretreated MPTMS‐Au‐CDtrodes were immersed in a stable sol solution (pH 3) containing (3‐aminopropyl)‐triethoxysilane (APTES) and tetraethoxysilane (TEOS). Polycondensation of the APTES and TEOS precursors was then achieved by applying a negative potential for a given period of time to generate a local pH increase at the electrode/solution interface and promote the deposition of the amine functionalized silica film adhering well to the electrode surface owing to the MPTMS monolayer acting somewhat as a “molecular glue”. Various parameters affecting the electrodeposition process have been studied and the film permeability to redox probes in solution was characterized by cyclic voltammetry. The amine‐functionalized silica film electrodes were then applied to the preconcentration of copper(II) species prior to their electrochemical detection by anodic stripping differential pulse voltammetry. Getting high sensitivity has however required the application of an electrochemical pre‐activation step as the majority of the organo‐functional groups were in the form of ammonium moieties (because the film was prepared from an acidic sol). This was achieved by applying a sufficiently negative potential to the electrode surface to reduce protons and increase consequently the amine‐to‐ammonium ratio within the film and, thus, the efficiency of the precocentration process. The resulting device was then optimized for copper(II) determination in hydroalcoholic medium, giving rise to a linear response in the 0.1–10 μM concentration range.
Electrochemically Deposited Polymer‐Coated Gold Electrodes Selective for 2,4‐Dichlorophenoxyacetic Acid
Authors: Weetall Howard H. , Hatchett David W. , Rogers Kim R. 
Published: July 2005

AbstractElectropolymerized membranes on gold electrodes doped with 2,4‐dichlorophenoxyacetic acid (2,4‐D) were prepared from a solution containing resorcinol, o‐phenylenediamine and 2,4‐D. Fourier Transform Infrared (FTIR) spectroscopy was used to evaluate the incorporation and interaction of 2,4‐D with the polymer matrix prior to and after the sensing experiments. The FTIR data indicate that 2,4‐D does not leach appreciably from the polymer matrix under experimental conditions employed for the sensing studies. The electrochemical current response for 2,4‐D is compared for the doped polymer‐coated and control polymer‐coated electrode. The response of the doped polymer‐electrode was dependent on increasing concentrations of 2,4‐D and 2,4‐dichlorophenol while unresponsive to benzoic acid.
Thinly Insulated Wire Cells – A New Device for Sensitive Contactless Conductivity Detection in Flow Analyses
Authors: Hoherčáková Zuzana , Opekar František , Štulík Karel 
Published: July 2005

AbstractVery simple contactless conductivity cells have been designed, suitable for detection in flow analytical techniques (classical HPLC, FIA, SIA, continuous flow, etc.) in which this detection has so far rarely been used. The cells consist of two wire electrodes covered with a very thin layer (units of μm) of an insulating material (the dielectric) and punctured through the walls of a plastic tubing at a close mutual distance (from tenths to units of a mm) and placed either across the tube or along the tube axis, so that the detection occurs within the space limited by the two electrodes. As the thickness of the dielectric layer is substantially smaller than that in common contactless conductivity cells used in CE, the AC current flowing between the electrodes is higher and the measuring sensitivity is enhanced. The principal operational characteristics of these detectors have been tested using KCl solutions and compared with those calculated from a simple theoretical model. It has been shown that this model permits theoretical description of these cell types and reasonable prediction of their behavior. Practical application has been demonstrated on a FIA determination of inorganic carbonate.
Performance of Impedimetric Biosensors Based on Anodically Formed Ti/TiO2 Electrodes
Authors: Mantzila Aikaterini G. , Prodromidis Mamas I. 
Published: July 2005

AbstractThe advantages and limitations of impedimetric sensors based on Ti/TiO2 architectures are described. Titanium dioxide (titania) was potentiostatically formed onto titanium electrodes of 2 mm diameter, at 10 and 30 V in 1 M H2SO4. The thickness of the titania layers was ellipsometrically determined to be 30 and 86 nm respectively and they are highly insulating with charge‐transfer resistances in the MΩ range, as they were measured with electrochemical impedance spectroscopy under specific experimental conditions. Low voltage anodization (<10 V) results to amorphous TiO2, whereas at higher applied voltages (>25 V), anatase is the predominant form. SEM images are indicative of quite smooth, compact coatings without any severe cracks.
Polymeric Membrane Lanthanum(III)‐Selective Electrode Based on N,N′‐Adipylbis(5‐phenylazo salicylaldehyde hydrazone)
Authors: Shamsipur Mojtaba , Ershad Sohrab , Samadi Naser , Esmaeilbeig Ahmad Reza , Kia Reza , Abdolmaleki Amir 
Published: July 2005

AbstractA recently synthesized azao‐containing Schiff's base N,N′‐adipylbis(5‐phenylazo salicylaldehyde hydrazone) was used as a suitable neutral ion carrier in construction of a highly selective La3+‐PVC membrane electrode. The electrode exhibits a Nernstian response with a slope of 19.4 mV decade−1 over a wide concentration range (1.0×10−6–1.0×10−2 M) and a limit of detection of 4.0×10−7 M (0.05 ppm). The electrode possesses a fast response time of ca. 10 s and can be used for at least 3 months without observing any deviation. The proposed electrode revealed excellent selectivity for La3+ over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.0–8.0. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of La3+ ions with EDTA and in determination of F− ion in some pharmaceutical preparations.
Simultaneous Determination of Platinum and Rhodium with Hydroxylamine and Acetone Oxime by Catalytic Adsorptive Stripping Voltammetry (CAdSV)
Authors: Huszał Sylwester , Kowalska Joanna , Sadowska Monika , Golimowski Jerzy 
Published: July 2005

AbstractThis paper describes a very sensitive catalytic adsorptive stripping voltammetry (CAdSV) procedure for the simultaneous determination of traces of platinum and rhodium in new supporting electrolyte containing hydroxylamine or acetone oxime and formaldehyde in sulfuric acid medium. Platinum and rhodium were pre‐accumulated simultaneously and after 120 s of accumulation time at 0.0 V, the achieved detection limits were equal 0.1 ng L−1and 0.2 ng L−1for platinum and rhodium respectively in the presence of acetone oxime and 0.6 ng L−1and 0.2 ng L−1for platinum and rhodium respectively in the presence of hydroxylamine. Described reagents were successfully applied to the determination of platinum and rhodium in plant material. Inductively coupled plasma mass spectrometry (ICP MS) was used as a reference method to the CAdSV measurements.
Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity
Authors: Milardovic Stjepan , Iveković Damir , Rumenjak Vlatko , Grabarić Božidar S. 
Published: July 2005

AbstractA novel electrochemical method for selective determination of antioxidant activity based on 2,2‐diphenyl‐1‐picrylhydrazyl | 2,2‐diphenyl‐1‐picrylhydrazin (DPPH⋅|DPPH) redox couple and biamperometric technique is proposed. Two identical glassy carbon disk electrodes were mounted in a classic electrochemical cell and the tested working potential difference was between 50 and 200 mV. The DPPH⋅|DPPH redox couple exhibited a high degree of reversibility. Selectivity of detector was tested by different antioxidant compounds in ethanol‐phosphate buffer solution, pH 7.40. The results of antioxidant activity of pure antioxidant compounds and of actual samples of beverages, expressed as Trolox equivalents and determined by proposed biamperometric and spectroscopic measurements, were in good correlation (R=0.9959). The detection limit for Trolox established by the applied biamperometry was 0.05 μM while the resulting current was linear up to 25 μM of Trolox.
Electrochemical Study of the Interactions of DNA with Redox‐Active Molecules Based on the Immobilization of dsDNA on the Sol‐Gel Derived Nano Porous Hydroxyapatite‐Polyvinyl Alcohol Hybrid Material Coating
Authors: Wang Huai‐Sheng , Wang Gui‐Xiang , Pan Qian‐Xiu 
Published: July 2005

AbstractA novel type of sol‐gel inorganic‐organic hybrid material coated on glassy carbon electrode used for immobilization of double‐stranded DNA (dsDNA) and study of dsDNA with redox‐active molecules was developed. The hybrid material coating was produced by sol‐gel method with nano hydroxyapatite (HAp)‐polyvinyl alcohol (PVA). The optimum composition of the hybrid material was first examined, and the morphology of the nano HAp‐PVA coatings was investigated with the help of Scanning Electron Microscope (SEM). DsDNA was immobilized in/on the nano HAp‐PVA hybrid coatings by adsorption and the characteristics of the dsDNA/HAp‐PVA/GCE were studied by cyclic voltammetry (CV) using the probes of Co(phen)$\rm{ {_{3}^{3+}}}$ and Fe(CN)$\rm{ {_{6}^{3-}}}$. The results indicate that the dsDNA can be immobilized on the nano porous HAp‐PVA coating effectively and its stability can satisfy the necessity of study on the interactions of dsDNA with redox‐active molecules on the electrode surface. Co(bpy)$\rm{ {_{3}^{3+}}}$ and Co(phen)$\rm{ {_{3}^{3+}}}$ were used as the model molecule to study the interactions of dsDNA with redox‐active molecules. Information such as ratio (KOx/KRed) of the binding constant for the oxidized and reduced forms of a bound species, interaction mode, including change in the mode of interaction, and “limiting” ratio K$\rm{ {_{Ox}^{^{o}}}}$/K$\rm{ {_{Red}^{^{o}}}}$ at zero ionic strength (μ) can be obtained using dsDNA/HAp‐PVA/GCE with about 2 μg of DNA samples.
Electrochemical Study of the Lipid‐Transfer Protein
Authors: Gorjanović Stanislava , Beljanski Miloš V. , Sužnjević Desanka 
Published: July 2005

AbstractElectrochemical study of barley grain lipid‐transfer protein (LTP) revealed that it may belong to the metal‐binding protein class. Using differential pulse polarography the presence of Cu(II) and Zn(II) ions in the native LTP structure was proved, as well as its affinity for binding Ni(II) ion. Application of a more sensitive electroanalytical technique, such as anodic stripping voltammetry with analyte preconcentration, revealed the presence of Pb(II) and Cd(II) ions and also enabled the following Hg(II) ion binding. Possible biological role of LTP in plant stress response and its contribution to barley phytoextraction potential are discussed.
Incorporation of Disposable Screen‐Printed Electrodes for Use in Capillary Electrophoresis End‐Column Amperometric Detection System
Authors: Tsai Dong‐Mung , Tai Hsiu‐Wen , Shih Pei‐Rong , Chang Ren‐Lin , Wu Han , Conte Eric D. , Zen Jyh‐Myng 
Published: July 2005

AbstractThe development and performance of an end‐column amperometric detection system integrated with disposable screen‐printed electrodes for capillary electrophoresis is presented. In this system, the electrode and capillary can be easily replaced and the capillary/electrode alignment procedure is straightforward. The use of easily replaceable screen‐printed electrodes offers a tremendous benefit for capillary electrophoresis applications requiring frequent replacement of the working electrode due to fouling. This simple and convenient system is very attractive for routine analyses by capillary electrophoresis with electrochemical detection. The separation and determination of uric acid in human urine is presented.
Electrochemical Characterization of Archaeological Tin‐Opacified Lead‐Alkali Glazes and Their Corrosion Processes
Authors: Doménech‐Carbó A. , Doménech‐Carbó M. T. 
Published: July 2005

AbstractThe electrochemical response of weathered and unweathered archaeological tin‐opacified glazes attached to paraffin‐impregnated graphite electrodes is described. Upon comparison with the square wave voltammetric response of SnO2, PbO and PbO2, Sn‐ and Pb‐centered reduction processes can be characterized. Reduction of Sn(IV) involves the stepwise formation of solid Sn(II) and Sn metal, successively, at potentials of −0.08 and −0.55 V vs. AgCl/Ag. Reduction of network‐modifier Pb(II) in glazes occurs at −0.5 V and is accompanied by the reduction of network‐forming Pb(IV) at potentials ranging from +0.65 to +0.20 V, confirming the presence of such centers in glazes. Voltammetric data suggest the presence of small amounts of Sn(II) resulting from the reduction of cassiterite during the firing process. A series of correlations between the peak currents can be established, indicating that the weathering process obeys a kinetic process rather than a equilibrium‐like situation.
A local‐analytic‐based discretization procedure for the numerical solution of incompressible flows
Authors: Pontaza J. P. , Chen H. C. , Reddy J. N. 
Published: July 2005

AbstractAn Erratum has been published for this article in International Journal for Numerical Methods in Fluids 2005, 49(8): 933. We present a local‐analytic‐based discretization procedure for the numerical solution of viscous fluid flows governed by the incompressible Navier–Stokes equations. The general procedure consists of building local interpolants obtained from local analytic solutions of the linear multi‐dimensional advection–diffusion equation, prototypical of the linearized momentum equations. In view of the local analytic behaviour, the resulting computational stencil and coefficient values are functions of the local flow conditions. The velocity–pressure coupling is achieved by a discrete projection method. Numerical examples in the form of well‐established verification and validation benchmarks are presented to demonstrate the capabilities of the formulation. The discretization procedure is implemented alongside the ability to treat embedded and non‐matching grids with relative motion. Of interest are flows at high Reynolds number, 𝒪(105)–𝒪(107), for which the formulation is found to be robust. Applications include flow past a circular cylinder undergoing vortex‐induced vibrations (VIV) at high Reynolds number. Copyright © 2005 John Wiley & Sons, Ltd.
Generic head models for atlas‐based EEG source analysis
Authors: Darvas Felix , Ermer John J. , Mosher John C. , Leahy Richard M. 
Published: July 2005

AbstractWe describe a method for using a generic head model, in the form of an anatomical atlas, to produce EEG source localizations. The atlas is fitted to the subject by a nonrigid warp using a set of surface landmarks. The warped atlas is used to compute a finite element model (FEM) of the forward mapping or lead‐fields between neural current generators and the EEG electrodes. These lead‐fields are used to localize current sources from the subject's EEG data and the sources are then mapped back to the anatomical atlas. This approach provides a mechanism for comparing source localizations across subjects in an atlas‐based coordinate system, which can be used in the large fraction of EEG studies in which MR images are not available. The Montreal brain atlas was used as the reference anatomical atlas and 10 individual MR volumes were used to evaluate the method. The atlas was fitted to each subject's head by a thin‐plate‐spline (TPS) warp. The spatial locations of a generic 155‐electrode configuration were used to constrain the warp. For the purposes of evaluation, dipolar sources were placed on the inner cortical surface in the atlas geometry and transferred to each subject's brain space using a polynomial warp. The parameters of the warp were computed using an intensity‐based matching of the atlas and subject brains, thus ensuring that the sources were placed at approximately the same anatomical location in each case. Data were simulated in the subject geometry and a dipole fit was performed on these data using an FEM of the TPS warped atlas. The source positions found in the warped atlas were transferred back to the original atlas and compared to the original position. Sources were simulated at 972 locations evenly distributed over the inner cortical surface of the atlas. The mean error over all 10 subjects was 8.1 mm in the subject space and 15.2 mm in the atlas space. In comparison, using an affine transformation of the electrodes into atlas space and an FEM model generated from the atlas produced mean errors of 22.3 mm in subject space and 19.6 mm in atlas space. With a standard three‐shell spherical model the errors were 27.2 mm in the subject space and 34.7 mm when mapped to atlas space. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.