bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetically controlled urease electrode
Authors: Hamann H. , Scheller F. , Kühn M. 
Published: February 2006

AbstractThe parameters and the measuring principle of a urease electrode are described. The urease is physically entrapped in cellulose triacetate on the active surface of a pH glass electrode with an internal reference electrode. The Michaelis constant of immobilized urease was similar to that of soluble enzyme (KM = 2.40 mmol/L). The average apparent enzyme activity amounts to 2 IU per sensor preparation. An enzyme loading factor of 0.04 was determined. It indicates kinetically controlled reaction conditions of the sensor. A fixed‐time measuring procedure provides a response time of 30 seconds and a linear response within a concentration range of 2 to 40 mmol/L urea in real biological samples (e.g., serum).
Selective determination of Cr(VI) oxyanions using a poly‐3‐methylthiophene‐modified electrode
Authors: Teasdale Peter R. , Spencer Melinda J. , Wallace Gordon G. 
Published: February 2006

AbstractPoly‐3‐methylthiophene‐modified platinum electrodes are useful for measuring trace levels of chromium(VI) oxyanions. Chromium(III) species do not interfere. The nature of the response is elucidated using scanning electron microscopy and electron microprobe analysis.
Tensammetric determination of a rhamnolipid at mercury electrodes
Authors: Emons Hendrik , Werner Gerhard , Haferburg Dieter , Kleber Hans‐Peter 
Published: February 2006

AbstractThe electrochemical and interfacial behavior of a rhamnolipid, (R)‐3‐[(R)‐3‐(O2‐α‐L‐rhamnopyranosyl‐α‐L‐rhamnopyranosyloxy)‐decanoyloxy]decanoic acid, was studied at mercury electrodes by phase‐selective ac voltammetry, dc tast polarography, differential pulse polarography, and electrocapillary measurements. This biocompound is not electroactive, but is strongly adsorbed at mercury electrodes. The differential capacity‐potential curves show well‐shaped tensammetric peaks. The peak height can be correlated with rhamnolipid bulk concentrations between 10−5 and 10−3 M (i.e., also in the range of micelle formation).
Electrochemical determination of chlorothion
Authors: Reddy T. N. , Reddy S. Jayarama 
Published: February 2006

AbstractThe electrochemical behavior of the pesticide chlorothion has been studied employing various voltammetric techniques and different supporting electrolytes. These studies covered a pH range from 2.0 to 12.0 in 25% DMF‐water mixtures. Adsorption complications were observed by ac polarography. Millicoulometry was employed for the determination of the number of electrons in the reduction process, and kinetic parameters were evaluated. The proposed reduction mechanism was based on the results obtained. Differential pulse polarography was used to develop an analytical method for chlorothion determination in trace levels.
Conductivity monitoring by an amperometric detector with a Cu(II)‐containing poly(3‐methylthiophene) electrode
Authors: Xue Zhi‐Lun , Karagözler A Ersin , Ataman O. Yavuz , Galal Ahmed , Amer Adel , Shabana R. , Zimmer Hans , Mark Harry B. 
Published: February 2006

AbstractA conducting, chemically synthesized, Cu(II)‐containing poly(3‐methylthiophene) powder was pressed into a pellet and used as the working electrode of a three‐electrode system in a thin‐layer amperometric cell unit to detect ionic analytes in an aqueous stream by flow‐injection analysis. The electrode response was linearly correlated with the applied voltage, which was varied between 0.2 and 3.0 V (vs. Ag/AgCI). It was shown that the electrode possesses favorable sensitivity and stability in comparison with other metallic electrodes such as stainless steel and Pt. During a period of more than a year, it showed no deterioration in its performance.
The effects of complexing agents and surfactants on the deposition and stripping processes in differential pulse anodic stripping voltammetry of metals at the hanging mercury drop electrode
Authors: Morrison Gregory M. P. , Florence T. Mark , Stauber Jennifer L. 
Published: February 2006

AbstractAn analysis scheme is presented that separates the individual effects of complexing agents and surfactants on the deposition and stripping steps in trace metal determination by differential pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode. The method involves DPASV measurements of total and electroactive (ASV‐labile) metal in pH 7.0 phosphate buffer before and after medium exchange, with and without acidification of the sample solution. Copper, lead, and cadmium were determined in the presence of Triton X‐100, a nonionic detergent, and the complexing agents fulvic and humic acids. Both the complexing agents and the surfactant affected deposition more than stripping, although Triton X‐100 had a significant effect on the stripping process. Triton X‐100 also acted as a complexing agent towards copper. Application of the analysis scheme to pristine and polluted freshwater samples showed that the decrease in the electroactivity of copper and lead was principally caused by the effect of surfactants on deposition. This study underlined the limitations of high‐frequency ASV techniques (e.g., DPASV) at a hanging mercury drop electrode for the determination of the toxic fraction of metals in water samples and raised questions about the usefulness of ASV copper complexing capacity titrations for water toxicity investigations.
The construction of a column‐shaped, thin‐layer ESR spectroelectrochemical cell for use at both ambient and low temperatures in nonaqueous solvents
Authors: Mu X. H. , Kadish K. M. 
Published: February 2006

AbstractThe construction and utilization of a column‐shaped in situ thin‐layer ESR spectroelectrochemical cell for both ambient and low temperature operation is reported. The working electrode is a columnshaped expanded platinum sheet of 9.4 × 4.0 mm that is placed in a 0.25 mm thick column‐shaped, thin‐layer chamber. The solution volume in the thin‐layer chamber is 12 μL, and the total solution volume in the cell ranges between 1 and 3 mL. The application of this cell is demonstrated by time‐resolved ESR spectra for electrooxidized porphyrins in methylene chloride solutions containing 0.3 M tetrabutylammonium perchlorate. The electrochemical behavior of this cell is also demonstrated by the oxidation of ferrocene under the same solution conditions at temperatures between 23 and −75°C. Well‐defined ESR spectra are obtained in as short as 5–10 seconds without data manipulation.
Amperometric determination of ozone in water at disposable graphite reinforcement carbon electrodes
Authors: Aoki Koichi , Kobayashi Atsushi , Kato Nakahide 
Published: February 2006

AbstractThe voltammetric reduction behavior of ozone in an acidic solution was examined at gold, platinum, glassy carbon, and graphite reinforcement carbon (GRC) electrodes. The GRC electrode, the lead of a mechanical pencil, exhibited a well‐defined ozone reduction wave at 0.8–0.9 V versus a saturated calomel electrode (SCE) on a flat base current, whereas gold and glassy carbon electrodes were insensitive or nonselective to ozone. The platinum electrode showed no base current and, hence, made background correction difficult. The response was not degraded by long exposures of the GRC electrode to the ozonized solution. The reduction of ozone at the GRC electrode was controlled by a sluggish charge‐transfer step and diffusion. Differential pulse voltammetric peak current showed a linear variation with ozone concentration up to the detection limit of 6 × 10−7 mol/dm3 ozone in acidic solutions. Residual ozone in tap water disinfected by chlorine was determined by the present method; a linear calibration curve was also obtained.
Mechanism of electrochemical oxidation of sulfamerazine at a pyrolytic graphite electrode
Authors: Goyal R. N. , Mathur N. C. , Bhargava S. 
Published: February 2006

AbstractThe electrochemical oxidation of sulfamerazine at a pyrolytic graphite electrode was studied in phosphate buffers with a pH ranging from 3.0 to 10.8. The 2e−, 2H+ oxidation of this compound produces an azo product. A possible reaction scheme is proposed on the basis of the results of linear sweep and cyclic voltammetry, coulometry, spectral studies, and product identification.
The determination of organochlorine compounds by adsorptive stripping voltammetry, part I: p,p′‐DDT and dieldrin
Authors: Li Chiang , James Bruce D. , Magee Robert J. 
Published: February 2006

AbstractThe environmentally persistent pesticides p,p′‐DDT and dieldrin may be determined simultaneously using an indirect adsorptive stripping voltammetric procedure that takes advantage of the very different binding capabilities of the two materials toward added iron(II). The method has been applied to the determination of these organochlorines in Australian bovine fat samples by employing benzyltrimethylammonium methoxide as a digestion medium. The limits of detection are 0.4 ppb (for p,p′‐DDT) and 0.7 ppb (for dieldrin), and the relative standard deviations (for 10 determinations) are 7.4 and 10.1%, respectively.
A new sensor for the determination of nicotine in tobacco products
Authors: Kang X. J. , Wang C. Y. 
Published: February 2006

AbstractA new nicotine sensor for the simple, rapid determination of nicotine in tobacco products without prior separation is described. The sensor is a coated graphite electrode with silicotungstic acid as the active material in polyvinyl chloride with di(2‐ethylhexyl) phthalate as the plasticizer. At pH 5.5–6.0, it provides a Nernstian response to nicotine over 10−1 to 10−6 M; the detection limit is 7.4 × 10−7 M, and the average slope is 58 mV/pN. The analytical recovery is 98.1 to 102.3%. Satisfactory results are obtained in comparison with silicotungstate gravimetric method and UV spectrometry.
Abrasive stripping voltammetric analysis of tin—bismuth
Authors: Scholz Fritz , Nitschke Lutz , Henrion Günter 
Published: February 2006

AbstractThe analysis of tin‐bismuth alloys using a new stripping technique, abrasive stripping voltammetry, is described. Small amounts of the alloy are transferred by mechanical abrasion from the solid alloy onto the surface of a paraffin‐impregnated graphite electrode. These traces are anodically stripped off with differential pulse voltammetry. The ratio of the tin and bismuth peak currents provide a measure of their relative content in the alloy. The determinations have standard deviations of about 5%. Peak potentials are reproducible within a 20‐mV range.
Flow‐injection amperometry of cysteine and glutathione at an electrode modified with a ruthenium‐containing inorganic film
Authors: Cox James A. , Gray Thomas J. 
Published: February 2006

AbstractA film that contains ruthenium oxide of mixed valences and cyanide (mvRuCN) on a glassy carbon electrode promotes the diffusion‐controlled oxidation of cysteine and glutathione at 0.92 V vs. Ag/AgCl. These mediated oxidations allow the determination of these thiols by flow‐injection amperometry in pH 2 solutions of 0.2 or 0.02 M K2SO4. Calibration curves are linear over about three orders of magnitude, and detection limits are in the submicromolar range with 7.5 μL injections. The sensitivity for cysteine is about 50 nA/μM with a flow rate of 1.0 mL/min. The throughput calculated on the basis of peak widths was 140 samples/h. Experimentally, with a manual injector, 60 samples/h were routinely analyzed. The sensitivity for glutathione in 0.2 M K2SO4 at pH 2 is somewhat lower, 36 nA/μM. A single electrode was used for hundreds of injections over a 2‐week period with no change in sensitivity. The mvRuCN‐coated electrode is operated in a potentiostatic mode; reactivation of the surface between series of experiments was not necessary. The electrode was stored at open circuit in contact with an electrolyte solution when not in use.
Resistance measurements as a simple diagnostic tool for ion‐selective electrode performance
Authors: Diamond Dermot , Regan Francis 
Published: February 2006

AbstractRecently, potentiometric sensors have found numerous applications involving on‐line monitoring in flow systems [1–4]. With trends toward the use of multielectrode arrays and electrode miniaturization, simple diagnostic tests for the routine assessment of device performance will become increasingly important. In this work, we present the possibility of using dc resistance measurements for this purpose. Mini‐sodium‐selective electrodes with polyvinyl chloride (PVC) membranes incorporating the ionophore methyl p‐t‐butylcalixaryl acetate [4, 5] were constructed, and a gradual increase in resistance with lifetime was observed. A lifetime mimicking study was set up in which leaching of the active components from the membrane was simulated by a series of dilutions, and the effect on overall electrode performance was monitored at each stage. Complete electrode malfunction has been shown to occur abruptly when the active membrane component concentration falls below a critical level. Electrode failure is accompanied by a sharp increase in membrane resistance.
Synthesis and potentiometric study of acyclic monoxadiamides as ionophores in ion‐selective electrodes
Authors: Attiyat Abdulrahman S. , Kadry Azza M. , Badawy Mohamed A. , Hanna Hishmatt R. , Ibrahim Yehia A. , Christian Gary D. 
Published: February 2006

AbstractSeven compounds of a new class of ionophores, acyclic monoxadiamides, were synthesized and tested for the potentiometric selectivity for lithium ion, in polyvinyl chloride (PVC) membrane electrodes. Four different plasticizers were studied: o‐nitrophenyloctyl ether (NPOE), o‐nitrophenylphenyl ether (NPPE), o‐nitrophenylbutyl ether (NPBE), and o‐nitrophenylbenzyl ether (NPBnE), as was the addition of trioctylphosphine oxide (TOPO). The ionophore o‐carboxyphenoxyacetic acid dimorpholide (Ig) exhibited sodium‐lithium selectivity, K, of 0.018 by the matched‐potential method in the presence of 1% TOPO using NPBE plasticizer. The presence of TOPO generally causes a substantial increase in the lithium selectivity, but it decreases the slopes of the calibration curves. Selectivities are reported for sodium, potassium, ammonium, barium, and calcium ions with respect to the lithium ion.
Precise analysis of silver by flow‐injection analysis with stripping voltammetric detection
Authors: Zhang Li Qun , Sturrock Peter E. 
Published: February 2006

AbstractFlow‐injection analysis (FIA) with voltammetric detection can be used in either the direct voltammetric or the stripping mode. In this study, a locally designed and constructed instrument with features not available in commercial instruments was used for the precise analysis of silver in aluminum. The carrier solution was 0.1 M Al(NO3)3 with 2 × 10−3 M HNO3. Silver solution was introduced by timed, partial‐loop injection. After cathodic deposition, a square‐wave or staircase voltammetric stripping sweep was applied. The data were recorded and analyzed by computer. Silver solutions of 8 × 10−8 to 4 × 10−5 M were tested. The standard deviations of repeat determinations of artificial samples varied from 0.12 to 0.78%. This precision was limited by the stability of the pump flow.
Simultaneous enzymatic determination of glucose and ascorbic acid using flow‐injection amperometry
Authors: Matuszewski Wojciech , Trojanowicz Marek , Ilcheva Liliana 
Published: February 2006

AbstractA flow‐injection procedure involving the glucose oxidase‐catalyzed oxidation of glucose and direct am‐perometric determination of ascorbic acid was developed for simultaneous determination of the two compounds. Experimental conditions of measurement, including the sample volume, flow rate, and delay coil length, were optimized to obtain satisfactory resolution for the two flow‐injection peaks. The principle of analytical interpretation of the obtained signal is presented, and the applicability of the determination of glucose and ascorbic acid in fresh fruit juices samples is illustrated.
Voltammetric behavior of perborate on prussian‐blue‐modified carbon paste electrodes
Authors: Boyer Abelkad , Kalcher Kurt , Pietsch Reinhold 
Published: February 2006

AbstractThe voltammetric behavior of the catalytic reduction of perborate at carbon paste electrodes modified with Prussian blue is compared with that of hydrogen peroxide. Good linearity is observed between the voltammetric current and the concentration from 1 to 100 ppm H2O2 as perborate. The influence of the paste composition and other variables is studied.
Electrochemical detection of aliphatic amines by HPLC after derivatization with 3‐(4‐hydroxyphenyl)propionic acid ester
Authors: Smith Roger M. , Ghani Asri Abdul 
Published: February 2006

AbstractBolton‐Hunter reagent, 3‐(4‐hydroxyphenyl)propionic acid‐N‐hydroxysuccinimide ester, has been investigated for its application as a derivatizing agent to introduce an electrochemically active group into aliphatic amines. The phenolic derivatives form readily and could be detected at low concentrations in chromatographic effluents.
Voltammetric behavior and measurement of nimorazole
Authors: Sivasankar P. , Reddy S. Jayarama 
Published: February 2006

AbstractThe electrochemical reduction behavior of nimorazole has been studied by employing dc polarography, differential pulse polarography, cyclic voltammetry, and chronoamperometry in the supporting electrolytes of pH ranging from 2.00 to 12.50. Parameters such as transfer coefficients, diffusion coefficients, and heterogeneous forward rate constant values are evaluated using these techniques. The analytical measurement of the drug is also discussed.
Ultramicroelectrodes for fast electrochemical kinetics
Authors: Andrieux C. P. , Hapiot P. , Savéant J.‐M. 
Published: February 2006

AbstractUltramicroelectrodes are shown to be extremely useful for investigating fast electrochemical kinetics due to the effects of decreased ohmic drops obtained by reducing electrode dimensions. Scan rates above 1 MV/s can be reached.
A battery‐powered, microprocessor‐controlled, programmable function generator for field‐based stripping voltammetry with conventional and microsized electrodes
Authors: Bond A. M. , Luscombe D. L. , Tan S. N. , Walter F. L. 
Published: February 2006

AbstractBattery‐powered, complementary metal oxide semiconductor (CMOS) devices have been used to develop a programmable function generator. When used in conjunction with commercially available, battery‐powered potentiostats or electrometers and recording devices, the technique of field‐based direct current stripping voltammetry becomes available. The instrumental performance of a range of modular, battery‐powered instruments has been evaluated with conventional and microsized electrodes and compared with ac‐powered laboratory instruments using conventionally sized electrodes. Stripping experiments with the field‐based instrument and with microelectrodes can be carried out under linear potential sweep conditions because the limit of detection is similar to that obtained with transient techniques at conventional sized electrodes. Other simplifications to the instrumentation and voltammetric procedures that are valuable in field‐based studies (e.g., neither stirring nor deoxygenation of the solutions is required) also are achieved by using microelectrodes and are illustrated by the determination of copper in a river water sample.
Cyclic voltammetry involving amalgam formation at mercury film microelectrodes
Authors: Ciszkowska Malgorzata , Penczek Martin , Stojek Zbigniew 
Published: February 2006

AbstractCyclic voltammetry involving amalgam formation at mercury microelectrodes is described experimentally and theoretically for reversible systems. Silver microdisks were used to support the mercury deposit during the preparation of electrodes. The ratio of the mercury film thickness to the disk radius is much lower than 1 (e.g., a 1 μm thick layer of Hg on a silver disk with a radius of 15 μm) justifies the name mercury film microelectrode. When the substrate is present in the solution, the original shape of the cyclic voltammograms (one or more cathodic waves followed by one or more anodic symmetrical peaks) is the result of the combination of spherical diffusion in the solution and restricted diffusion in the mercury film. When the substrate is present initially in the mercury phase, an anodic symmetrical peak is followed by a negligibly small cathodic peak. The alternate dimension implicit and the alternate direction Galerkin methods were used in the calculations.
Glassy carbon microband electrochemical detector for high‐performance liquid chromatography
Authors: Zadeii Javad M. , Mitchell Rosalind , Kuwana Theodore 
Published: February 2006

AbstractAn elecrochemical microband thin‐layer flow cell that incorporates a thin glassy carbon electrode was fabricated and tested. The microband, tested with ferrocyanide and catecholamine oxidation, exhibited properties of a microelectrode with excellent electroactivity and signal‐to‐noise (S/N) response. For the chromatographic determination of several catecholamines at the 100 fmol level, the relative standard deviation as measured by the peak height ranged from 3–8%. The detection limit for DOPAC was 5 fmol (S/N = 3). The microband thin‐layer cell gives an improved S/N ratio at an applied potential of 0.6 V vs. Ag/AgCl compared to that of a conventionally sized glassy carbon electrode. The small surface area of the microband allows rapid stabilization of chromatographic background (baseline) following the application of the potential. The microband thin‐layer flow cell has a volume of 5 μL and exhibits a flow‐rate‐independent response, reduced ohmic drop, and gradient elution capability. The microband cell has great potential for commercialization as a universal detector for liquid chromatography.
Analytical microelectrode voltammetry with minimal instrumentation
Authors: Lafleur Rick D. , Myland Jan C. , Oldham Keith B. 
Published: February 2006

AbstractThe manual recording of near‐steady‐state diffusion currents at inlaid disk or shrouded hemispherical microelectrodes provides a simple and accurate analytical method for a variety of electroactive species in the micromolar and millimolar concentration ranges. The only instrumentation needed is a battery, a chain of resistors, and a battery‐powered picoammeter. A two‐electrode cell suffices. Ferrocene in an acetonitrile solution can be analyzed at concentrations as low as 2.0 μM, but the detection limits are higher in aqueous solutions. Using a simple microcell, as little as 100 pmol of ferrocene could be detected. This work resembles some of the earliest voltammetric studies, but the use of smaller electrodes provides a firmer theoretical foundation to the experiments.
Flexible ultramicroline electrodes
Authors: Lay Peter A. , McAlpine Neale S. , Harding Geoffrey L. 
Published: February 2006

AbstractFlexible ultramicroline electrodes have been made from a variety of materials, including Au, Pt, Ir, and C. The thickness of these materials ranges from 3.5 nm (approximately 13 atoms thick) to 700 nm. The smallest electrodes are comparable to the smallest rigid line electrodes produced by other techniques. The electrode material is sandwiched between flexible polymer supports, and the bottom is cut with a scalpel to produce the working face of the ultramicroline electrode. The special method of attaching the films to the polymer support allows a high degree of electrode flexibility without causing fractures and concomitant increases in resistance and altered electrode characteristics. The flexibility of these electrodes offers the potential for easy fabrication of a variety of electrode configurations, including spirals, rings, concentric rings, linear arrays, and ring‐disc electrodes. Examples of the electrochemical behavior of ultramicroline and ultramicroring electrodes are described and are similar to those of rigid ultramicroelectrodes that are produced using other technologies. The carbon ultramicroline electrodes are somewhat more susceptible to mechanical damage than the metallic electrodes when they are flexed, and the resistivity increases on bending, thus indicating some fracturing of the film. Nonetheless, they can still be bent into various geometries and are electrochemically useful.