bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow characteristics of a versatile wall‐jet or radial‐flow thin‐layer large‐volume cell for electrochemical detection in flow‐through analytical systems
Authors: Soucaze‐Guillous Benoît , Kutner Włodzimierz 
Published: May 2005

AbstractFlow characteristics of a versatile large‐volume flow‐through electrochemical cell, which features exchangeable disk, ring‐disk or microdisk working electrodes, are presented. The cell operates in a radial‐flow thin‐layer, wall‐jet or wall‐tube mode, under amperometric or voltammetric conditions, being therefore suitable for flow analytical techniques, such as high performance liquid chromatography (HPLC) and flow injection analysis (FIA). The operation mode is selected by using the inlet capillary either of a flat or conical nozzle and by suitably adjusting the nozzle‐to‐electrode distance. The cell is equipped with a micrometer screw which allows for adjusting of this distance to be as small as 10 ± 5 μm. The inlet solution stream is centered axially against the working electrode surface. Under radial‐flow thin‐layer conditions, flow‐through detection at a ring‐disk electrode benefits from shielding and collecting properties which are enhanced as compared to those for the rotating ring‐disk electrode conditions. The HPLC extracolumn effects due to detection were determined by the peak variance analysis of a mixture of regio isomers of nitrobenzene derivatives. Despite the large (35mL) geometric cell volume, the effective detection volume of the cell is of the microliter order. Therefore, the cell is suitable for detection both in the analytical and microbore‐column HPLC. Due to the large geometric cell volume, solution composition can be different, under wall‐jet conditions, for detection than that for HPLC separation. Hence, in situ postcolumn modification of the mobile phase or analyte is feasible.
Differential pulse cathodic stripping voltammetric determination of manganese(II) and manganese(VII) at the 1‐(2‐pyridylazo)‐2‐naphthol‐modified carbon paste electrode
Authors: Khoo Soo Beng , Soh Ming Koon , Cai Qiantao , Khan Miriam R. , Guo Si Xuan 
Published: May 2005

AbstractA carbon paste electrode modified with 1‐(2‐pyridylazo)‐2‐naphthol was fabricated and used to preferentially accumulate Mn(II) at open circuit. After medium exchange, the accumulated Mn(II) at the electrode surface was electrochemically oxidized. The hydrated MnO2 thus formed was then cathodically stripped using differential pulse voltammetry. Various factors influencing the accumulation and stripping were studied. An optimized procedure was then developed for the determination of Mn(II). Mn(VII) could also be determined by chemical conversion to Mn(II) using acidified H2O2. Following this, the Mn(VII) concentration could be obtained by subtraction. Under optimum conditions, a detection limit of 6.9 × 10−9 M Mn(II) (0.38 ppb) was found for 200s accumulation. For 8 determinations, each of Mn(II) concentrations of 1.00 × 10−6 M, 1.00 × 10−7 M and 1.00 × 10−8 M, relative standard deviations of 2.90%, 4.46% and 7.20% were obtained, respectively. Selected metal ions were tested for interferences and it was found that, when determining 1.00 × 10−6 M Mn(II) (150s accumulation), Co(II), Hg(II) and Fe(II) at 1.00 × 10−5M interfered. These interferences were readily eliminated by masking with complexing agents such as sodium citrate and sodium diethyldithiocarbamate. The developed method was tested using a certified sample and then applied to the determination of manganese in seawater.
Organized self‐assembled lipoyl‐β‐cyclodextrin derivative monolayer on a gold electrode
Authors: He Pingang , Ye Jiannong , Fang Yuzhi , Suzuki Iwao , Osa Tetsuo 
Published: May 2005

AbstractAn organized self‐assembled monolayer of β‐cyclodextrin (β‐CD) derivatives on a gold surface has been prepared using two lipoyl‐β‐cyclodextrin derivatives with different chain lengths, which are more flexible than heptakis (dodecyl sulfide) β‐cyclodextrin. The surface coverage of the monolayers were found to be in agreement with the surface coverage of a highly organized monolayer of β‐CD. It has been revealed by cyclic voltammetry that the β‐CD derivative monolayers have the characteristics of: (a) selective barriers blocking the permeability for those molecules, such as ferricyanide, and p‐aminophenol, which are incapable of complexing with β‐CD; and (b) have selective transport for electroactive organic species, such as ferrocene carboxylic acid and hydroxyquinone, which can form host‐guest inclusion complexes with β‐CD receptors. The selective transport can be controlled by blocking the β‐CD cavities with some guest molecules such as cyclohexanol borneol and ursodeoxycholic acid, and the controlling mode can be expected for detection of organic compounds.
Electrochemical behavior of mutagenic nitro and amino derivatives of carbazole
Authors: Carlier Roger , Raoult Eugène , Tallec André , Andre Vèronique , Gauduchon Pascal , Lancelot Jean‐Charles 
Published: May 2005

AbstractThe electrochemical behavior of nitro and amino carbazole derivatives has been investigated. In aprotic medium, both in reduction and oxidation, the electrochemical process is complicated by “father‐son” protonation reactions. In protic medium, the hydroxylamines resulting from 4‐electron reduction of nitrocarazoles are unstable in very acidic medium, but relatively stable in acetic or ammoniacal buffer, except for 3‐hydroxyl‐aminocarbazole; reduction of amino‐nitrocarbazoles leads to unstable hydroxylamines. Oxidation of aminocarbazoles is a 2‐electron process, the 2‐amino compounds being more difficult to oxidize than the 3‐amino derivatives. The relationships between these electrochemical behaviors and mutagenic properties of the studied compounds are also discussed.
In situ electrochemistry of Ru(NH3) in a perfused rat heart
Authors: Schoenfisch Mark H. , Pemberton Jeanne E. , Ovadia Marc , Levy Margaret 
Published: May 2005

AbstractSimple two‐electrode potential sweep and potential step electrochemical measurements are reported in a perfused living rat heart prepared using a modified in situ Langendorff preparation. Cyclic voltammetry of Ru (NH3) at Pt electrodes is performed in vivo after retrograde aortic perfusion of Ca2+‐and albumin‐free, oxygenated Krebs buffer containing Ru(NH3) to assess uniformity of perfusion. Four types of voltammetric response are observed depending on the placement of the working electrode. These types are distinguished on the basis of the relative contributions of diffusive and hydrodynamic mass transport as mnifest in the shapes of the current‐potential curves. Chronoamperometric measurement of double layer charging was used to estimate extracellular tissue resistance. These chronoamperometric experiments are performed in buffer solutions by small potential steps around a set potential of non‐Faradaic activity. Tissue. resistance was estimated to be ca. 598 ± 138 Ω from the chronoamperometric data. The electrochemical responses observed from both measurements exhibit good reproducibility between individual heart preparations.
Flow‐injection potentiometric detection of metal ions based on tungsten oxide electrode
Authors: Chen Zuliang , Alexander Peter W. 
Published: May 2005

AbstractThe use of a tungsten oxide electrode for potentiometric flow‐injection analysis of transition metal ions is described. The effect of a variety of experimental conditions, including the carrier pH, the types of ligands and their concentrations, was studied. It was found that the best sensitivity for the ions tested was obtained using EDTA as a ligand. The electrode exhibited a linear response for Fe3+, Cu2+, Pb2+ and Ca2+ in the range of 2.5 × 10−4 M to 2 × 10−3 M using with 1 × 10−3 M EDTA at pH 5.0 as carrier. The detection limits were found to be between 1 × 10−5 to 5 × 10−5 M. Reproducibility for Fe3+ was about 1.7% with a stable baseline potential.
Electrochemical oxidation of isoniazid catalyzed by the 2,2,6,6,‐tetramethyl‐4‐acetylpiperidine‐1‐oxy radical and its analytical application
Authors: Tong Jian , Dang Xiao‐Jun , Li Hu‐Lin 
Published: May 2005

AbstractThe electrochemical oxidation of isoniazid catalyzed by the 2,2,6,6‐tetramethyl‐4‐acetylpiperidine‐1‐oxy(TMAPO) radical at a glassy carbon electrode in phosphate buffer solution has been studied. The rate constant of the reaction for isoniazid and the oxoammonium salt evaluated by rotating disk voltammetry is (2.36 ± 0.12)×104 dm3 mol−1 s−1. The electrochemical behavior of the TMAPO radical and the stability of the oxoammonium salt have also been investigated by cyclic voltammetry. The linear relationship between the catalytic peak current and the isoniazid concentration over the range of 4 × 10−4‐2 × 10−3M was used for the determination of isoniazid in isoniazid tablets. A method for analysis of isoniazid was established.
Thin‐film gold electrodes produced by magnetron sputtering. Voltammetric characteristics and application in batch injection analysis with amperometric detection
Authors: Brett Ana Maria Oliveira , Matysik Frank‐Michael , Vieira M. Teresa 
Published: May 2005

AbstractThin‐film gold electrodes were produced by radio‐frequency sputtering using a polyvinyl chloride foil as substrate. The voltammetric behavior was characterized in various electrolyte solutions. In alkaline and neutral aqueous solutions reliable voltammetric measurements can be performed while in acidic media some nondefined phenomena occur. A novel type of electrode for batch injection analysis (BIA) is presented which is produced from circular pieces of the thin‐film material. This electrode can be used for BIA in conventional voltammetric cells. Pulsed amperometric detection is demonstrated to be viable with thin‐film gold electrodes and shows analytical advantages over constant‐potential detection in the BIA of hydrogen peroxide.
Anodic stripping voltammetric determination of vanadium(V) using a carbon paste electrode modified in situ with cetyltrimethylammonium bromide
Authors: Stadlober Monika , Kalcher Kurt , Raber Georg 
Published: May 2005

AbstractA method for the voltammetric determination of vanadium(v) using a carbon paste electrode in situ modified with cetyltrimethylammonium bromide (CTAB) is described. Vanadium is preconcentrated at the electrode surface via its anionic oxalate complex from acidic solution (0.01 M oxalic acid, 0.25 mM CTAB, pH 2.2) at a potential of −0.9 V [vs. the saturated calomel electrode (SCE)]. Simultaneously during accumulation, vanadium(v) in the complex is reduced to its tetravalent state. Differential pulse anodic stripping voltammetry exploiting the reoxidation can be used for the determination of trace levels of vanadium(v). Linearity between current and concentration exists for a range of 5 to 200 μg.L−1 Vv with a preconcentration time of 1 min. The limit of detection (calculated as 3 σ) is 0.07 μg.L−1 with a preconcentration time of 10 min.
The coulometric determination of chemical oxygen demand
Authors: Pamplin Kim L. , Johnson Dennis C. 
Published: May 2005

AbstractThe chemical oxygen demand (COD) of solutions containing various organic compounds is calculated from the net faradaic charge (Qnet) estimated for the total electrolytic oxidation of CrIII generated during oxidative degradation of the organic compounds in acidic media containing excess CrVI. Values of Qnet for conversion of CrIII to CrVI are estimated from the linearized chronoamperometric data plotted as In {itat, t} vs. t. This procedure is preferred over determinations of Qnet from the total integrals of itot over the entire electrolysis period because of large errors that can result from uncertainty in the background current (ibkg) for t → ∞. The proposed coulometric procedure offers the benefit that reagent solutions can be reused, thereby minimizing the need for disposal of wastes containing toxic CrVI. This procedure was applied in a single digest solution for consecutive determinations of COD. Average COD values for potassium acid phthalate and glucose were 103.8% (s ‐ 6.0, N ‐ 10) and 100.2% (s ‐ 4.2, N ‐ 11), respectively, based on the theoretical degradation to CO2. In comparison for these same samples, an EPA approved method, based on colorimetric determination of CrIII, gave COD values of 101.4% (S ‐ 1.4, N ‐ 5) and 100.1% (s ‐ 1.4, N ‐ 5) of the theoretical. Statistical tests indicate no significant difference in the COD values determined for these compounds using the coulometric and EPA methods.
Applications of the channel flow cell for UV‐visible spectroelectrochemical studies. Part 2: Transient signals
Authors: Wang Rui Lin , Tam Kin Yip , Marken Frank , Compton Richard G. 
Published: May 2005

AbstractThe use of the channel flow cell for ultraviolet‐visible (UV‐vis) spectroelectrochemical experiments has been developed to determine the diffusion coefficients of electrogenerated species by means of monitoring the transient absorbance response resulting from a potential step at a working electrode immediately upstream of the incident spectrophotometric beam. The technique is applied to measure the diffusion coefficient of tris(4‐bromophenyl)amine (TBPA) radical cation in acetonitrile at 25°C. It is shown that the diffusion coefficient of electrogenerated TBPA radical cation (1.64 ± 0.02 × 10−5 cm2 s−1) is very close to that of the parent molecule (1.57 ± 0.03 × 10−5 cm2 s−1).
Application of a large assembly of microelectrodes to the study of cytochrome‐c and other redox proteins
Authors: Bianco Pierre , Haladjian Jean , Fletcher Stephen 
Published: May 2005

AbstractA novel microelectrode assembly containing more than 1000 carbon microdisks has been used to study the interfacial electron transfer kinetics of cytochrome c and several other redox proteins. It is demonstrated that near‐steady‐state current–voltage curves can be obtained without solution stirring, and without significant mains interference or capacitive charging currents. In addition, it is demonstrated that concentrations of redox proteins as low as 1 μM can be detected in solution. Finally, it is shown that the surfaces of carbon microdisk assemblies can be successfully coated with thin films of poly(ester sulfonic acid), which allows reactants to be studied in a membrane‐like environment.
Response of the jalpaite membrane copper(II) ion‐selective electrode in marine waters
Authors: De Marco Roland , Mackey Denis J. , Zirino Alberto 
Published: May 2005

AbstractThe response of the Orion 94‐29 CuII ion‐selective electrode (ISE) [employing a jalpaite membrane] in seawater has been related to levels of free CuII yielding results for the Derwent River and San Diego Bay that are 2 to 3 orders of magnitude higher than those for the Pacific Ocean. Response data for the electrode in acidified seawater at pH 2 are internally consistent with total CuII levels determined using differential pulse anodic stripping voltammetry (DPASV) and graphite furnace atomic absorption spectrometry (GFAAS). It has been found that, even in acidified seawater, the organic ligands influence the response of the electrode, and this effect can be compensated successfully by either analyzing UV‐photooxidized seawater and/or using a standard addition technique. The assigned ISE results for total CuII in acidified seawater fall within ± (0.1–0.5) pCu unit of values determined using GFAAS. Electrode drift in seawater can be minimized by using a polished electrode that has been conditioned in seawater for 24 h. The improved response rate of a conditioned ISE minimizes electrode soaking times and sample contamination through membrane corrosion.
Arrays of gold microelectrodes made from split integrated circuit chips
Authors: Nascimento Valberes B. , Augelli Márcio A. , Pedrotti Jairo J. , Gutz Ivano G. R. , Angnes LúCio 
Published: May 2005

AbstractA simple and inexpensive way to fabricate arrays of gold microelectrodes is proposed. Integrated circuit chips are sawed through their middle, normal to the longest axis, leading to destruction of the silicon circuit and rupture of the gold wires that interconnect it with the external terminals. Polishing the resulting rough surface converts the tips of the wires embedded in the chip halves into arrays of gold microdisks of about 25 μm diameter. The number of active microelectrodes (MEs), of an array depends on the number of pins in the chip, n, being typically (n/2)‐4. These MEs can be used individually or externally interconnected in any combination. X‐ray images of the chips and micrographs of the resulting surface of the polished arrays have revealed variable distances between neighbor MEs, which are however, larger than 10 times the radius of the disks. This feature of the MEs prevents diffusional cross‐talk between electrodes. The use of these microdisk electrodes for analytical purposes exhibits sigmoidal voltammograms, and chronoamperometric experiments confirm the nonlinear i vs. t1/2 plots, typical for processes where radial diffusion prevails, Satisfactory uniformity was observed for the response of each electrode of an array, indicating similarity of geometry and disk areas. The potentialities of these MEs were demonstrated by the determination of cadmium at ppb levels using square wave voltammetry with preconcentration. Due to the relative ease with which these MEs can be manufactured and their good performance in (chemical) analysis, wide applications in electrochemistry and electroanalysis is envisioned.
Quantification of the adsorption of methyl viologen on pyrex glass using a renewable perfluorosulfonated ionomer carbon paste electrode
Authors: Pailleret Alain , Rapicault Stéphane , Degrand Chantal 
Published: May 2005

AbstractSquare wave voltammograms of methyl viologen (MV2+) were recorded at a renewable Nafion‐loaded carbon paste electrode immersed in 20 mL of phosphate buffer solution (pH 7.4) contained in a beaker‐type electrochemical cell (Pyrex glass; contact area = 33 cm2). From the calibration plot obtained in the concentration range 0.01–2.4 μM, it could be concluded that the maximum surface excess of MV2+ adsorbed on Pyrex glass (0.24 nmol cm−2) was reached at concentrations above 1.4 μM. The adsorption isotherm presented a sigmoidal shape characteristic of attractive interaction. From this plot, it was evaluated that the maximum depletion of MV2+ in solution (28%) did not occur at the lowest concentrations, but in nearly micromolar solutions. This result emphasizes the unavoidable and random errors which are involved when MV2+ solutions are purposely diluted in Pyrex glassware. The MV2+ adsorption proceeds to a less extent on Duran borosilicate glass and/or in acid or alkaline medium.
Potentiometric stripping analysis and anodic stripping voltammetry for measurement of copper(II) and lead(II) complexation by fulvic acid: A comparative study
Authors: Town Raewyn M. 
Published: May 2005

AbstractThe utility of potentiometric stripping analysis (PSA) for studying the interaction of fulvic acid with CuII and PbII at pH 1.8 and 4.8 was assessed. The impact of fulvic acid on both the deposition and stripping steps was considered. In contrast to results obtained by anodic stripping voltammetry, fulvic acid influenced both these steps in PSA, and to different degrees. Surface active substances have been claimed to have self‐compensatory effects in PSA; this work shows that this is not valid for heterogenous natural complexants such as fulvic acid.
Nickel determination in osteoblast‐like cell culture medium by adsorptive cathodic stripping voltammetry with a mercury microelectrode
Authors: Morais Simone , Carvalho Graça Simões , Sousa João Paulo 
Published: May 2005

AbstractThe purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast‐like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square‐wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10−4 mol L−1; ammonium chloride buffer: 0.10 mol L−1 (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10−9 mol L−1 for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays.
Electrochemical detection of herbicides and plant growth regulators at membrane glassy carbon electrodes
Authors: Bianco Pierre , Aghroud Nadia 
Published: May 2005

AbstractMembrane glassy carbon electrodes modified with cation‐exchangers (Eastman AQ‐29D, laponite, or polystyrene sulfonate) entrapped between the membrane and the carbon surface were used to study the electrochemical behavior of herbicides and plant growth regulators from the quaternary ammonium family. Cations are shown to incorporate in the entrapped solutions containing negatively charged cation‐exchangers, because of favorable electrostatic interactions. In the case of nonelectroactive cations, collection of mepiquat, chlormequat and difenzoquat from the bulk solution is assessed from the competition in ion‐exchange equilibrium between one of the above‐mentioned cations and the electroactive diquat cation. An attractive property results from the use of spinach ferredoxin as cation‐exchanger inside the membrane electrode. Promotion of ferredoxin is shown to be evidenced as a result of the collection of nonelectroactive cations from the bulk solution. Prospects of such modified membrane electrodes in the environmental field are discussed.
Voltammetric behavior and determination of bismuth on sodium humate modified carbon paste electrode
Authors: Wang Chunming , Sun Qiaoyu , Li Hulin 
Published: May 2005

AbstractThe preconcentration and voltammetric behavior of BiIII on a sodium humate modified carbon paste electrode was studied by means of cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The proposed measurement involves an initial nonelectrolytic preconcentration step in which BiIII is complexed by the surface modifier in a solution of 0.05 M KNO3‐0.0106 M HNO3 (pH 2.0) and a subsequent electrochemical scan step in which the preconcentrated BiIII was reduced and then oxidized promptly in supporting electrolyte of 0.5 M HNO3. The resulting DPSV anodic current was proportional to the concentration of BiIII ion over the range of 4.78 × 10−8–1.44 × 10−5 M. The detection limit was 4.78 × 10−8 M. The proposed method was used to determine bismuth in various samples. Various factors affecting the electrode behavior were also investigated at the same time.
Controlling the selectivity of glassy carbon flow detectors using covalently attached monolayers
Authors: Downard Alison J. , Roddick Alisa D. 
Published: May 2005

AbstractSignificant improvements in selectivity for amperometric detection in flow analysis are achieved at covalently modified glassy carbon electrodes. Flow detectors modified with p‐alkylbenzene (alkyl = methyl, decyl) and p‐phenylacetate monolayers demonstrate how selectivity may be obtained on the basis of solute hydrophobicity and charge. The modified electrodes are stable under hydrodynamic conditions and in aqueous and mixed aqueous/organic carrier streams.