bluuebunny/crossref_metadata_2025_split huggingface dataset:
Square‐Wave Voltammetry of Cathodic Stripping Reactions. Diagnostic Criteria, Redox Kinetic Measurements, and Analytical Applications
Authors: Gulaboski Rubin , Mirčeski Valentin , Komorsky‐Lovrić Šebojka , Lovrić Milivoj 
Published: March 2004

AbstractA comparative study of different types of cathodic stripping reactions under conditions of square‐wave voltammetry is presented. Cathodic stripping processes involving reactions of second order as well as reactions coupled by adsorption of the reacting ligand are analyzed The inherent parameters, controlling the overall voltammetric behavior of each cathodic stripping electrode reaction are derived. The criteria for qualitative distinguishing of each mechanism are established as well as a methodology for redox kinetic measurements is proposed. The influence of the parameters of the excitation signal on the properties of the voltammetric response is analyzed in order to find optimal conditions for analytical application. The theoretical results are illustrated by the experiments with a series of uracil derivatives.
New Ion‐Pair Based All‐Solid‐State Surfactant Sensitive Sensor for Potentiometric Determination of Cationic Surfactants
Authors: Matešic‐Puac Ruzica , Sak‐Bosnar Milan , Bilic Mate , Grabaric Bozidar S. 
Published: March 2004

AbstractCationic surfactants of different types were determined using a few potentiometric sensors based on ion‐pair complexes (dodecyldimethylbenzylammonium dodecylsulfate, dodecylmethylbenzylammonium dodecylbenzensulfonate, tetrahexadecylammonium dodecylsulfate and Hyamine (benzethonium dodecylsulfate)) as sensing materials. The response of the all‐solid state surfactant sensitive electrode based on a Teflonized graphite conducting substrate, coated with a PVC membrane containing sensing material, was investigated in the solutions of Hyamine and hexadecyltrimethylammonium ion in the concentration range from 1 μM to 10 mM. Potentiometric surfactant cation titration has been performed using sodium dodecylsulfate as titrant and an ion‐pair‐based surfactant sensitive electrode as a potentiometric indicator. Several commercial surfactant products have also been titrated and the results were compared with those obtained with two‐phase standard titration method.
Label‐free DNA Hybridization Based on Coupling of a Heated Carbon Paste Electrode with Magnetic Separations
Authors: Wang Joseph , Flechsig Gerd‐Uwe , Erdem Arzum , Korbut Olga , Gründler Peter 
Published: March 2004

AbstractThe technique of electrically heated carbon paste electrodes is applied for label‐free detection of DNA hybridization after magnetic isolation. Coupling of both techniques leads to highly selective and sensitive detection of DNA hybridization. Minimal contributions of nonhybridized DNA are thus coupled to an enhanced signal. Application of elevated temperatures during the accumulation step yields a max. 6‐fold enhancement of guanine oxidation signals compared to room temperature deposition. Use of noncomplementary nucleic acids gives no significant peaks at room or elevated temperatures. The noise level remained unaffected. Variation of the target concentration results in linear calibration plots under hot accumulation conditions.
Determination of Cr(VI) Using a Pulse Amperometric Method with an Ionophore‐Immobilized Membrane Electrode
Authors: Choi Young‐Woo , Moon Seung‐Hyeon 
Published: March 2004

AbstractA pulse amperometric method for the determination of Cr(VI) in aqueous solution has been investigated with an ionophore‐immobilized membrane electrode. The double potential step chronoamperometry was applied to measure the current for the facilitated transfer of Cr(VI) by the membrane with N,N,N′,N′‐tetrakis(3‐aminopropyl)‐1,4‐butanediamine (DABAm4) coated on a silver electrode. The current responses were stably detected by the pulse amperometry while voltage pulses, ΔE=−240 mV, of short duration of 50 ms were employed at the interval of 5 s. In the range of 1.65–81.3 μM, Cr(VI) in water could be selectively determined in the presence of various interfering anions below 100 μM without removal of Cr(VI) from the interferences using an ion exchange column.
Novel Potentiometric PVC‐Membrane and Coated Graphite Sensors for Lanthanum(III)
Authors: Ganjali Mohammad Reza , Kiani‐Anbouhi Roya , Shamsipur Mojtaba , Poursaberi Tahereh , Salavati‐Niasari Masoud , Talebpour Zahra , Emami Mahdi 
Published: March 2004

AbstractPreliminary theoretical studies revealed the selective complexation of bis (2‐mercaptoanil) diacetyl (BMDA) with La3+ over several alkali, alkaline earth and heavy metal ions. Thus, novel PVC‐based membrane (PBM) and coated graphite membrane (CGM) sensors for La(III) based on BMDA were prepared. The electrodes display Nernstian behavior over wide concentration ranges (i.e., 1.0×10−5–1.0×10−1 M for PBM and 1.0×10−6–1.0×10−1 M for CGM). The potential response of sensors was pH independent in the range of 4.0–8.0. The sensors possess satisfactory reproducibility, fast response time (<15 s), and specially excellent discriminating ability for La3+ ions with respect to most of the cations. The membrane sensor was used as an indicator electrode in potentiometric titration of lanthanum ions with EDTA. The coated graphite membrane electrode was applied in determination of fluoride ions in mouth wash preparations.
Study of the Electrochemical Behavior of Disperse Blue 1‐Modified Graphite Electrodes. Application to the Flow Determination of NADH
Authors: Stergiou Dimitrios V. , Prodromidis Mamas I. , Veltsistas Panayotis G. , Evmiridis Nikolaos P. 
Published: March 2004

AbstractThe preparation and the electrochemical study of Disperse Blue 1‐chemically modified electrodes (DB1‐CME), as well as their efficiency for the electrocatalytic oxidation of NADH is described. The proposed mediator was immobilized by physical adsorption onto graphite electrodes. The electrochemical behavior of DB1‐CME was studied with cyclic voltammetry. The electrochemical redox reaction of DB1 was found to be reversible, revealing two well‐shaped pair of peaks with formal potentials 152 and −42 mV, respectively, (vs. Ag/AgCl/3M KCl) at pH 6.5. The current Ip has a linear relationship with the scan rate up to 800 mV s−1, which is indicative for a fast electron transfer kinetics. The dissociation constants of the immobilized DB1 redox couple were calculated pK1=4 and pK2=5. The electrochemical rate constants of the immobilized DB1 were calculated k1°=18 s−1 and k2°=23 s−1 (Γ=2.36 nmol cm−2). The modified electrodes were mounted in a flow injection manifold, poised at +150 mV (vs. Ag/AgCl/3M KCl) and a catalytic current due to the oxidation of NADH was measured. The reproducibility was 1.4% RSD (n=11 for 30 μM NADH) The behavior of the sensor towards different reducing compounds was investigated. The sensor exhibited good operational and storage stability.
3‐Indoxyl Phosphate as an Electrochemical Substrate for Horseradish Peroxidase
Authors: Fanjul‐Bolado Pablo , González‐García María Begoña , Costa‐García Agustín 
Published: March 2004

AbstractIn this work 3‐indoxyl phosphate (3‐IP), an alkaline phosphatase substrate, is demonstrated to be a suitable substrate for horseradish peroxidase (HRP). HRP catalyzes the oxidation of 3‐IP in presence of hydrogen peroxide (H2O2) generating the product indigo blue, which is an aromatic heterocycle compound insoluble in aqueous solutions. This product was easily converted into its soluble parent compound indigo carmine (IC) (by addition of fuming sulfuric acid to the reaction media) which has a reversible voltammetric peak at the formal potential of −0.15 V (vs. Ag pseudo‐reference electrode) when a screen‐printed carbon electrode (SPCE) is used. Parameters that influence the enzymatic reaction, such as pH, temperature, substrate concentration and reaction time have been optimized. Moreover, the enzyme apparent kinetic constants (Vmax, KM) for both substrates (3‐IP and H2O2) have been calculated. Indirect measurements of HRP activity in solution were carried out not only by cyclic voltammetry but also using amperometric detection in a flow system. The detection limits were 6.86×10−12 and 5.68×10−12 M, respectively. Thus, 3‐IP is the first substrate that could be used for alkaline phosphatase (AP) and HRP, the most common enzymatic labels in affinity assays.
The Electrochemical Behavior of α‐Ketoglutarate at the Hanging Mercury Drop Electrode in Acidic Aqueous Solution and Its Practical Application in Environmental and Biological Samples
Authors: Yang Li , Yang Zhengbiao , Zhang Min , Ni Haiyan , Ji Ming , Tang Yongzheng , Yang Xiaodi , Long Xiufen , Bi Shuping 
Published: March 2004

AbstractThe voltammetric behavior of α‐ketoglutarate (α‐KG) at the hanging mercury drop electrode (HMDE) has been investigated in acetate buffer solution. Under the optimum experimental conditions (pH 4.5, 0.2 M NaAc‐HAc buffer solution), a sensitive reductive wave of α‐KG was obtained by linear scan voltammetry (LSV) and the peak potential was −1.18 V (vs. SCE), which was an irreversible adsorption wave. The kinetic parameters of the electrode process were α=0.3 and ks=0.72 1/s. There was a linear relationship between peak current ip, α‐KG and α‐KG concentration in the range of 2×10−6–8×10−4 M α‐KG. The detection limit was 8×10−7 M and the relative standard deviation was 2.0% (Cα‐KG=8×10−4 M, n=10). Applications of the reductive wave of α‐KG for practical analysis were addressed as follows: (1) It can be used for the quantitative analysis of α‐KG in biological samples and the results agree well with those obtained from the established ultraviolet spectrophotometric method. (2) Utilizing the complexing effect between α‐KG and aluminum, a linear relationship holds between the decrease of peak current of α‐KG Δip and the added Al concentration C in the range of 5.0×10−6–2.5×10−4 M. The detection limit was 2.2×10−6 M and the relative standard deviation was 3.1% (C=4×10−5 M, n=10). It was successfully applied to the detection of aluminum in water and synthetic biological samples with satisfactory results, which were consistent with those of ICP‐AES. (3) It was also applied to study the effect of AlIII on the glutamate dehydrogenase (GDH) activity in the catalytically reaction of α‐KG+NH$\rm{ {_{4}^{+}}}$+NADH⇌L‐glutamate+NAD++H2O by differential pulse polarography (DPP) technique. By monitoring DPP reductive currents of NAD+ and α‐KG, an elementary important result was found that Al could greatly affect the activity of GDH. This study could be attributed to intrinsic understanding of the aluminum's toxicity in enzyme reaction processes.
Development of a Tubular Sensor Based on a Polypyrrole‐Doped Membrane for the Potentiometric Determination of the Dodecylsulfate Anion in a FIA System
Authors: Álvarez‐Romero Giaan Arturo , Morales‐Pérez Adriana , Rojas‐Hernández Alberto , Palomar‐Pardavé Manuel , Ramírez‐Silva Maria Teresa 
Published: March 2004

AbstractPotentiostatic polymerization of polypyrrole doped with dodecylsulfate anion (DS−) was carried out in situ over a tubular composite (graphite‐epoxy resin) support in order to develop a potentiometric DS− sensor (TISE) suitable for flow injection analysis (FIA). The sensibility of the TISE was maximized using the SIMPLEX algorithm in terms of the concentration of the pyrrole monomer, the concentration of DS−, the potential imposed and polymerization time. Response times between 2 and 4 minutes were observed. The analytical parameters obtained with the flow system were compared with those obtained in batch studies. In both, flow and batch analysis, potential vs. DS− concentration curves displayed two linear regions with different slopes. Flow analysis for DS− ion brings a total linear range of 1.58×10−5 M to 3.88×10−3 M with a maximum sensibility of 36.4 mV/concentration decade, meanwhile in batch studies the total linear range found was of 6.31×10−6 M to 1.0×10−3 M with a maximum sensibility of 54.49 mV. The flow system response pH range was from 5 to 8. The reproducibility in terms of the relative error of the mean of different experiments was 1.58%. Two salient features of the system designed and built are worthy of mention: the sensor presented high selectivity to the dodecyl sulfate ion as compared to other inorganic anions including other anionic surfactants. The sensor lifetime in the FIA system by means of the sensibility changes was found to be of approximately four months.
Electrochemical Overoxidation of Polyindole and Its Cation‐Permselective Behavior
Authors: Ghita Mihaela , Arrigan Damien W. M. 
Published: March 2004

AbstractPolyindole films prepared by potentiostatic growth in dichloromethane solution were subjected to overoxidation studies in aqueous media. Overoxidation at potentials greater than 1.1 V (vs. SCE) in 0.1 M KNO3 or 0.1 M H2SO4 was possible. Overoxidation in 0.1 M NaOH resulted in mechanically unstable films which were not adherent to the electrode surface. The overoxidation process in 0.1 M KNO3 involved removal of one electron per four indole monomer moieties in the polymer film. Nucleophilic attack led to introduction of carboxylate functionality and to cation permselective behavior, as tested by cyclic voltammetry and hydrodynamic voltammetry of hexamminoruthenium(III) and hexacyanoferrate(III). Such films may be useful in various electrochemical sensor applications.
Square‐Wave Voltammetric Transfer of Silver Ions Across the Water|1,2‐Dichloroethane Interface
Authors: Sherburn Amanda , Arrigan Damien W. M. , Dryfe Robert A. W. , Boag Neil M. 
Published: March 2004

AbstractRecently reported studies on the transfer of silver ions across the aqueous|1,2‐dichloroethane interface using cyclic voltammetry (CV), facilitated by organic phase electrolyte anions, have been augmented by square‐wave voltammetry (SWV) and square‐wave stripping voltammetry (SWSV) studies and by consideration of the possible transfers of additional metal cations. Using SWV and SWSV, detection limits have been improved, from the 0.02 mM obtained by CV, to 1.4 μM (SWV) and 2 nM (SWSV). Additional studies show that mercury(I and II) ions, platinum(II) ions and gold(III) ions are also transferable across this interface, to differing extents. Of these three ions studied, highest sensitivity is achieved for the gold species.
Highly Stable Voltammetric Detection of Nitroaromatic Explosives in the Presence of Organic Surfactants at a Polyphenol‐Coated Carbon Electrode
Authors: Wang Joseph , Thongngamdee Sompong , Kumar Arun 
Published: March 2004

AbstractA polyphenol‐coated screen‐printed carbon electrode is used for highly sensitive voltammetric measurements of the 2,4,6‐trinitrotoluene (TNT) explosive in the presence of surface‐active substances. The permselective/protective polyphenol coating offers excellent resistance to surfactant fouling, while allowing facile transport of the target TNT. High levels of gelatin, humic acid and sodium dodecyl sulfate (SDS) (up to 50 mg/L) have negligible effects upon the square‐wave voltammetric TNT response. The TNT peak current and potential remain nearly the same in the presence of these organic macromolecules, as compared to substantial peak suppressions and shifts at the bare electrode. Control of the electropolymerization time was used for achieving the desired exclusion of interfering surface‐active macromolecules while allowing transport of the target TNT. The response for ppm levels of TNT is highly linear and stable for prolonged operations in the presence of surface‐active substances. By meeting the high sensitivity, selectivity, stability, portability and low‐cost demands, such voltammetric sensing holds great promise for field‐based voltammetric monitoring of nitroaromatic explosive compounds.
Electrochemical Investigation of Binding of Heavy Metal Ions to Turkish Lignites
Authors: Pehlivan Erol , Richardson Amie , Zuman Petr 
Published: March 2004

AbstractAdsorption and desorption of Cu2+, Pb2+, Cd2+, Ni2+ and Zn2+ ions on samples of lignites (young brown coal) from three areas in the vicinity of Konya (Anatolia, Turkey) were followed using the polarographic method of analysis. This method enables the determination of free metal ions in suspensions containing both small and colloidal particles of lignite. Effects of pH, nature of the metal ion, and origin of the lignite on its adsorption capacity were followed. Binding is only between 5 and 30% reversible, indicating that ion exchange is not the predominant factor. The role of the size and shape of cavities inside pulverized lignite and of the functional groups inside these cavities was considered.
Cyclic Voltammetric Study of the Oxidation of Catechols in the Presence of Cyanide Ion
Authors: Nematollahi Davood , Alimoradi Mohammad , Husain S. Waqif 
Published: March 2004

AbstractElectrochemical oxidation of catechols has been studied in the presence of cyanide ion as nucleophile in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate that the participation of catechols in the Michael reaction with cyanide ion to form the corresponding o‐dihydroxybenzonitrile. Based on an EC mechanism, the homogeneous rate constants were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results.
Catalytic Au Electrodes Based on SAMs of per(6‐deoxy‐6‐thio‐2,3‐di‐O‐methyl)‐β‐cyclodextrin
Authors: Chmurski Kazimierz , Koralewska Anna , Temeriusz Andrzej , Bilewicz Renata 
Published: March 2004

AbstractA three‐step sequential self‐assembly procedure was applied in preparing gold electrodes modified in a stable and controlled way by a monolayer of thiolated β‐cyclodextrin (β‐CD), with methylene blue (MB) included in its cavity as the active component of the monolayer, and octanethiol as the nonelectroactive spacer blocking the electrode surface not occupied by β‐CD. MB acted as a mediator of electrons with respect to a solution soluble analyte, H2O2, and provided electrical contact between the electrode and solution resident enzyme, laccase, catalyzing reduction of oxygen to water.
Selective Electroanalytical Assay for Cysteine at a Boron Doped Diamond Electrode
Authors: Nekrassova Olga , Lawrence Nathan S. , Compton Richard G. 
Published: March 2004

AbstractThe electrochemical oxidation of the cysteine‐quinone adduct has been examined as a means of providing an electroanalytical cysteine specific detection protocol. The appliance of square‐wave voltammetry allowed 0.5 μM as a limit of detection. The effects of various biologically relevant interferences including other thiols were studied and found to present no change in the voltammetric profile. The practical applicability and efficiency of the methodology was probed through the determination of cysteine concentration in growth tissue medium.
Electrochemistry at High Pressures: A Review
Authors: Giovanelli Debora , Lawrence Nathan S. , Compton Richard G. 
Published: March 2004

AbstractHigh pressure electrochemical studies are potentially dangerous and less immediately implemented than conventional investigations. Technical obstacles related to properties of the working electrode material, preparation of its surface, availability of suitable reference electrodes, and the need for specially designed high pressure equipment and cells may account for the relative lack of experimental data on electrochemistry at high pressures. However, despite the stringent requirements for system and equipment stability, significant developments have been made in recent years and the combination of electrochemical methods with high hydrostatic pressure has provided useful insights into the thermodynamics, kinetics, and other physico‐chemical characteristics of a wide range of redox reactions. In addition to fundamental information, high pressure electrochemistry has also lead to a better understanding of a variety of processes under non‐classical conditions with potential applications in today's industrial environment from extraction and electrosynthesis in supercritical fluids to measurement of the pH at the bottom of the ocean. The purpose of this article is to detail the experimental pressurizing apparatus for electroanalytical measurements at high pressures and to review the relevant literature on the effect of pressure on electrode processes and on the properties of aqueous electrolyte solutions.
Analysis, testing, and implementation of seismic isolation of buildings in Chile
Authors: De la Llera Juan C. , Lüders Carl , Leigh Patricio , Sady Henry 
Published: March 2004

AbstractThis article summarizes the work done by the authors in seismic isolation over the past six years in Chile. First, a general evaluation of the optimal values of the yield level of the isolation system is performed, focusing on the idea of, but not restricted to, the use of lead–rubber bearings. These optimal values are obtained for two performance objectives: to minimize the base shear in the superstructure and to control the isolator deformation. They were used in the design and construction of two important isolated buildings that are described herein; a short description of the more relevant aspects of the design and implementation of the isolation system in these two buildings is also presented. Furthermore, results from a long testing program conducted on more than 260 full‐size elastomeric isolators are summarized and discussed. It is shown that these experimental results enable the elastomeric compounds to be characterized quite accurately by testing reduced‐scale specimens with elastomer thickness identical to that used in the full‐size isolators. Also, results from isolator constitutive modeling, scragging, and creep in the short term are briefly discussed. Inelastic analyses were performed in the structures in order to evaluate realistic interstory drift and floor acceleration response reduction factors due to the isolation design used. It is shown that in spite of the isolation system, minor inelastic excursions of the primary structure are expected, leading to smaller drift and acceleration reduction factors than those obtained from assuming an elastic response of the superstructure. In any case, seismic isolation is shown to be a very competitive alternative, technically and economically, for building design in Chile. Although it may be difficult to extrapolate this experience to other environments, the results presented herein demonstrate that seismic isolation is a technique that can be effectively used to mitigate seismic hazards in developing countries. Copyright © 2004 John Wiley & Sons, Ltd.
Frequency domain modal analysis of earthquake input energy to highly damped passive control structures
Authors: Takewaki Izuru 
Published: March 2004

AbstractA new complex modal analysis‐based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non‐linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis‐based method is developed. The importance of overdamped modes in the energy computation of specific non‐proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis‐based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd.