bluuebunny/crossref_metadata_2025_split huggingface dataset:
Submicromolar determination of NADH by means of graphite and glassy carbon electrochemical transducers
Authors: Palleschi G. , Rathore H. S. , Mascini M. 
Published: February 2006

AbstractReduced nicotinamide adenine dinucleotide (NADH) has been determined at submicromolar levels (the detection limit was 0.05 μmol/L) by using graphitized and glassy carbon electrodes obtained from different sources. Preliminary studies compared the sensitivity, stability, and reproducibility of such sensors during NADH measurements in linear‐sweep voltammetry as well as at constant applied potential. High purity graphite carbon from Ringsdorff has been found to be the most suitable for NADH oxidation. To regenerate the electrodes after each voltammetric scan, washing with a large volume of distilled water under stirring conditions is required. When the sensitivity of the electrode decreases drastically, the sensor surface must be ground and polished with alumina. The nature of the carbon surface has a pronounced effect on the NADH response.
Comparison of the voltammetric behavior of adsorbed or dissolved unsaturated alcohols at vacuum‐annealed and electrochemically cycled Pt(111) and Pt(polycrystalline) electrodes
Authors: Batina Nikola , Kahn Bruce E. , Lin Chiu‐Hsun , McCargar James W. , Salaita Ghaleb N. , Hubbard Arthur T. 
Published: February 2006

AbstractThese studies compare the voltammetric behavior of solutions and adsorbed layers of the following unsaturated alcohols: benzyl alcohol (BZA), 4‐pyridylcarbinol (4PC), allyl alcohol (AA), propargyl alcohol (PGA), cis‐2‐butene‐1,4‐diol (CBED), and 2‐butyne‐1,4‐diol (BYD). They were undertaken for well‐characterized Pt(111) electrode surfaces which were either annealed in an ultrahigh vacuum (UHV) or electrochemically cycled, as well as for annealed (UHV) Pt(poly). Electrochemical oxidation of BZA, AA, PGA, CBED, and BYD in aqueous fluoride electrolyte proceeds in two stages: first the alcohol moiety is oxidized to CO2 (0.4 V), followed by oxidation of the resulting adsorbed hydrocarbon (alkene, alkyne, or phenyl, 1.0 V); 4PC is relatively inert. The alcohol moiety in 4PC, which is located opposite the pyridine ring from the surface, does not undergo oxidation at an appreciable rate. in fact, 4PC effectively passivates the surface and poisons the electrochemical activity. Electrochemical cycling of the annealed Pt(111) single‐crystal surface greatly increases the oxidation rates of the aliphatic alcohols and, to a lesser extent, increases the oxidation rate of BZA. The oxidation rate enhancement is somewhat smaller if the electrode is electrochemically cycled in the presence of the alcohol. The majority of the difference effected by cycling can be observed after only one cycle. Voltammetry on polycrystalline Pt surfaces resembles that on cycled Pt(111) surfaces for PGA and AA, but resembles that on cycled Pt(111) surfaces for PGA and AA, but resembles that on annealed Pt(111) more closely for the diols CBED and BYD.
Glucose enzyme electrode preparation by the codeposition of platinum and glucose oxidase onto glassy carbon
Authors: Gunasingham Hari , Tan Chee‐Beng 
Published: February 2006

AbstractA glucose enzyme electrode was fabricated by the simultaneous electrodeposition of enxyme and platinum particles onto a glassy carbon substrate. The electrode combines the electrocatalytic activity of platinum and the stability of glassy carbon. The application of the electrode in flow‐injection detection of glucose is shown. A wide linear range and good precision is possible.
The use of chemisorbed electrocatalytic polymers for detection in flowing solutions
Authors: Barisci Jose N. , Wallace Gordon G. , Wilke Ellen A. , Meaney Mary , Smyth Malcolm R. , Vos Johannes G. 
Published: February 2006

AbstractThe use of a chemically modified electrode for amperometric detection in flowing solutions is described. The modifier is a ruthenium‐containing polymer ([Ru(bpy)2(PVP)5Cl]Cl) that exhibits electro‐catalytic properties. The polymer‐coated electrodes are less prone to fouling (product adsorption) problems and show enhanced sensitivity for various dithiocarbamate metal complexes and nitrite ions. Limitations of the chemisorbed polymer coatings are discussed.
Chemically modified carbon paste and carbon composite electrodes
Authors: Stará Věra , Kopanica Miloslav 
Published: February 2006

AbstractCarbon paste electrodes and composite carbon electrodes modified by 20% silica gel (30 μm) within the electrode material exhibit many properties typical of a strand of carbon fiber microelectrodes in voltammetric measurements. Charged and uncharged species were studied on these electrodes; phenol, ferricyanide, and potassium ethylxanthogenate yield sigmoidal voltammograms with limiting currents that are virtually independent of the supporting electrolyte concentration. Phenol can be determined in the absence of the electrolyte in water containing up to 30% acetonitrile. Modified carbon composite electrodes are suitable for the determination of potassium ethylxanthogenate for the purposes of controlling flotation processes.
Electrochemical behavior of spiroplatin at carbon paste and platinum electrodes
Authors: Mebsout F. , Kauffmann J.‐M. , Patriarche G. J. , Vereecken J. , Christian G. D. 
Published: February 2006

AbstractThe voltammetric behavior of the hydrolyzed platinum(II) antitumor drug spiroplatin has been investigated at carbon paste and platinized platinum electrodes. The compound is oxidized to the corresponding platinum(IV) species at positive potentials near the solvent oxidation potential. On reversal of the potential scan, two 2‐electron reduction steps occur on the carbon paste electrode, resulting in formation of platinum metal, as confirmed by scanning electron microscopy. In the presence of chloride, different reduction peaks associated with the formation of chloro structures are observed. These depend on the chloride ion concentration. The oxidation‐reduction steps become more reversible at the platinum electrode. The nature of the oxidized species and the amount of platinum deposit were found to be related to the concentration of free chloride ions. Because the carbon paste electrode has the ability to differentiate the different oxidized forms upon reduction, its use is recommended for studying these compounds.
Automated potentiometric end point determination in the Lane‐Eynon titration of reducing sugars
Authors: Alexander Peter W. , Hartati Rahayu D. , Curtin John 
Published: February 2006

AbstractAn instrumental method which closely matches the Lane‐Eynon titration is evaluated with microcomputer interfacing for determining reducing sugars by titration into boiling Fehling's solution. Titrations using copper or platinum as indicator electrodes for end point detection gave millivolt changes at the end point, varying from 18 to 220 mV depending on the electrode couple used, and relative standard deviations of 0.44–0.67% for the precision of measured end, point volumes. Titration data measured with a copper‐platinum electrode couple are acquired in real time for 58 raw sugar samples with reducing sugar content varying from 0.10 to 0.61%. Linear regression correlation of the potentiometric titration data and the standard Lane‐Eynon method gives a correlation coefficient of 0.9960.
Electroanalytical study of indomethacin
Authors: Arcos Julia , López‐Palacios Jesús , Sánchez‐Batanero Pedro 
Published: February 2006

AbstractThe Polarographic behavior of indomethacin has been studied with the aim of developing a procedure for its determination in pharmaceutical tablets. In the study of the electrode process, linear‐sweep voltammetry and controlled potential coulometry were also considered. The electrode reactions are shown to be strongly affected by variations in pH. Adsorption phenomena appear at certain pH values. Detection limits and sensitivity in the determination of indomethacin were obtained by using tast polarography (TP), differential pulse polarography (DPP), and pseudoderivative pulse polarography (NPP).
Analytical applications of metallized membrane electrodes
Authors: Opekar František 
Published: February 2006

AbstractA survey of the analytical applications of metallized membrane electrodes with both porous and nonporous membranes is presented with emphasis on the methods for determining substances in solution that can be transferred to the gas phase and, thus, determined by the membrane electrode (pneumatoamperometry and pneumatopotentiometry). In this way, a high sensitivity of determination and considerable selectivity can be attained.
An enzyme‐amplified electrochemical immunoassay for thyrotropin
Authors: Cardosi Marco F. , Birch Stephen W. , Smith Brian M. , Johannsson Axel 
Published: February 2006

AbstractAn enzyme‐amplified, two‐site immunoassay utilizing electrochemical detection has been developed for thyrotropin. The lower detection limit of the assay (mean plus 2 standard deviations of the zero standard) is 0.046 ml. U/L, and the precision is good, giving a working range of 0.2 to 18.5 ml. U/L (determined as a percentage dose CV < 10). The assay of a 25 μL serum sample in an eight‐well microtitre strip takes approximately 1 hour. The electrochemical detection is carried out in situ using a custom‐built electrode array comprising eight graphite indicator electrodes and eight stainless‐steel cathodes. This arrangement, together with a fast multiplexer, allows the quasisimultaneous measurement of eight samples. A good correlation between this method and a radioimmunometric assay (IRMA) procedure was obtained for the determination of thyroid‐stimulating hormone (TSH) in patient samples. The relevant properties of a novel graphite material developed for this work are described.
Fabrication of a microbial carbon dioxide sensor using semiconductor fabrication techniques
Authors: Suzuki Hiroaki , Kojima Naomi , Sugama Akio , Takei Fumio , Ikegami Kasumi , Tamiya Eiichi , Karube Isao 
Published: February 2006

AbstractA disposable bacterial CO2 sensor has been fabricated using semiconductor techniques by immobilizing autotrophic bacteria on the sensitive area of a miniature Clark‐type oxygen electrode and covering them with another gas‐permeable membrane consisting of a negative photoresist formed directly on the gel. The response time of the CO2 sensor was 2 to 3 minutes. A linear relationship for the NaHCO3 concentration was obtained between 0.5 and 3.5 mM at 30°C and pH 5.5. The CO2 sensor can be used up to 10 times.
Induction time in stripping voltammetry at solid electrodes
Authors: Hepel Maria , Bruckenstein Stanley 
Published: February 2006

AbstractThe processes and phenomena causing the appearance of induction times in stripping voltammetry are analyzed. Induction times are observed experimentally at solid electrodes. Two such examples are presented for cathodic stripping voltammetry of phenylthiourea and methylthiourea at silver rotating disk electrodes in alkaline solutions. Induction times are inherent to the formation of deposits via the nucleation and growth mechanism, which is common in stripping voltammetry at solid electrodes. Numerical calculations of the deposition charge (which is directly related to the stripping peak current) as a function of the deposition time have been performed for the hemispherical model with progressive nucleation.
Rapid coulometry with a porous carbon felt electrode using iodide or ferrocyanide ion mediators
Authors: Uchiyama Shunichi , Suzuki Shuichi , Hamamoto Osamu 
Published: February 2006

AbstractThe oxidizing agents of iodide and ferrocyanide ions, such as 1,4‐benzoquinone and the iodate ion have been determined by rapid (9–25 seconds) coulometry. The electrolytic solution is confined to the pores of the carbon felt electrode and the sample is added to the carbon felt surface, which is maintained at a fixed potential. Current efficiencies approached 100% for sample concentrations ranging from 1 × 10−5 to 1 × 10−1 M with relative standard deviation of 0.6–2.2%. The determination of residual chlorine in drinking water has been carried out using the same coulometric cell, and the results obtained by the present method are in good agreement with those obtained by the orthotolidine method.
Stripping analysis at the automatic voltammetric electrode
Authors: Yarnitzky Chaim N. 
Published: February 2006

AbstractA small pump connected to an automatic voltammetric electrode gently and reproducibly agitates the cell solution as required for efficient stripping analysis. The pump consists of a membrane and an electromagnetic vibrator. The movement of the membrane is accompanied by periodic convection due to pressure changes in the gas enclosed in the space between the membrane and the solution. The mass transport is as effective as in common magnetic stirring. The usefulness of the new system for stripping analysis (as compared to analysis carried out in common cells) is demonstrated.
Voltammetric determination of the stability constants of copper(II) complexes with folic acid
Authors: Maali Nagwa Abo El , Ghandour Mahmoud A. , Vire Jean‐Claude , Patriarche Gaston J. 
Published: February 2006

AbstractBoth differential pulse polarography (DPP) and differential pulse anodic stripping voltammetry (DPASV) have been applied to the determination of the conditional stability constants of copper(II)‐folic acid complexes. The polarographic technique does not allow the investigation of these reactions in neutral media due to the interference of a hydroxy copper complex. DPASV exhibits two complexes with 1:1 and 1:3 stoichiometry at pH 7.4. The addition of 2 mM phosphate buffer affects the complexation mechanism; three different species are formed. In a weakly acidic medium (pH 4.5), only one complex is evidenced, but, due to the protonation of the pterin moiety of folic acid, which is the active site for complexation, an increase of the proton concentration inhibits the complex formation. Copper(II) ions are shown to be more strongly complexed than lead and cadmium ions under the same conditions. Using d.p.a.s.v. Copper(II) can be determined over the 4 × 10−6 to 2 × 10−5 M concentration range in the presence of 5 × 10−6 M folic acid.
Stabilization of a ruthenium polymer‐modified electrode for use in flowing solution analysis
Authors: Wallace G. G. , Meaney M. , Smyth M. R. , Vos J. G. 
Published: February 2006

AbstractVarious methods have been investigated to stabilize a ruthenium polymer‐modified electrode for use in flow‐injection analysis. These include treatment with ultraviolet irradiation as well as coating the modified electrode with electrochemically generated conductive and nonconductive polymer layers. The stabilization procedures tested proved effective in improving the operational half‐life of a nonstabilized electrode from 8 hours to more than 48 hours for the determination of test analyte species such as nitrite and nickel bis‐2‐hydroxyethyl dithiocarbamate.
Determination of tin(IV) oxide with a mixed carbon paste electrode and using computerized instrumentation
Authors: Tascón M. Luz , Vázquez M. Dolores , Pardo Rafael , Batanero Pedro Sánchez , Iza Jon 
Published: February 2006

AbstractAn analytical method is proposed for the determination of tin(IV) oxide in solid casiterite samples (at the milligram level) by using a mixed carbon paste electrode. The construction of an analog‐digital interface for the acquisition and processing of voltammetric data with a microcomputer is also described, together with the associate software. The proposed system and method are applied to solid samples with good agreement to results obtained with gravimetric analysis.
Polarographic determination of molybdenum in water
Authors: Pardo Rafael , Barrado Enrique , Castrillejo Yolanda 
Published: February 2006

AbstractA direct method for determination of Mo(VI) at trace levels in water samples is described. The reaction used, between salycilaldoxime, bromate, and Mo(VI), produces a differential pulse catalytic peak proportional to the Mo(VI) concentration. A detection limit of 0.12 μg/L can be achieved. The procedure, which has been applied to several natural and tap water samples by means of a standard additions method, achieved satisfactory results. A computer‐based system that controls these experiments is also discussed.
Use of mercury drop electrodes for polarographic measurements in flowing solutions
Authors: Kubiak Wladyslaw W. 
Published: February 2006

AbstractThe use of dropping mercury, hanging mercury drop, and static mercury drop electrodes in flow analysis and liquid chromatography is reviewed. Theoretical considerations (particularly flow rate dependence), measuring techniques, designs of flow‐through detectors, and methods of oxygen removal in flow systems are discussed. A brief guide to flow applications of mercury electrodes is also given.
Improved anodic stripping voltammetric measurements of silver by codeposition with mercury
Authors: Wang Joseph , Li Ruiliang , Huiliang Huang 
Published: February 2006

AbstractSignificant improvements in the stripping voltammetric response of silver are observed in the presence of low levels (20 μg/L) of mercury. The formation of amalgam results in a higher sensitivity, sharper peak, improved reproducibility, and extended linear range when compared to analogous measurements in the absence of mercury. Even though mercury has a slightly more negative stripping potential than silver, no interference is observed because of its low level. The silver response is evaluated with respect to mercury and silver concentrations, deposition time and potential, coexisting metals, organic surfactants, and other variables. The detection limit is 1.4 × 10−10 M (16‐min deposition), and the relative standard deviation (at 5 × 10−8 M) is 1.3%. Applicability to speciation work and river water samples is demonstrated. Additional work in this laboratory should lead to further improvements.
The application of adsorptive voltammetry to the study of the interaction of human chronic lymphocytic leukemia cells with two murine monoclonal antibodies raised against them
Authors: Lannon Bernadette , O'Kennedy Richard , Flores Juana Rodriguez , Fennelly James J. , Smyth Malcolm R. 
Published: February 2006

AbstractThe electrochemical behavior of whole and lysed chronic lymphocytic leukemia (CLL) cells, as well as that of two murine anti‐CLL antibodies, has been studied using differential pulse adsorptive voltammetry. Conditions have been optimized for the determination of these cells and antibodies with respect to the accumulation potential, the accumulation time, the scan rate, and the pulse amplitude. This technique has also been used to investigate the interaction of CLL cells with two monoclonal antibodies in solution.
Mechanism of nickel(II) ion reduction in the presence of ampicillin
Authors: Sužnjević D. , Kapetanović V. 
Published: February 2006

AbstractThe nature of polarographic precurrents of nickel(II) ion in the presence of ampicillin as well as the behavior of ampicillin in the electrical double layer has been investigated, and the reduction mechanism has been proposed. The rate of the homogeneous chemical reaction was calculated to be kf = 1.5 × 104 L mol−1 s−1.
Differential pulse polarographic investigation of nickel(II)‐5‐hydroxytryptophan complex
Authors: Kapetanović V. , Milovanović L. 
Published: February 2006

AbstractPolarographic studies illustrate that Ni(II) ion forms a complex with 5‐hydroxytryptophan (aqueous medium, pH = 7.20, μ = 0.2). The stoichiometric composition of the complex and its concentration and thermodynamic stability constants (log K = 4.46 and log β = 4.60) have been determined.
An electrochemical sensor for hydrogen peroxide based on peroxidase adsorbed on a spectrographic graphite electrode
Authors: Jönsson G. , Gorton L. 
Published: February 2006

AbstractHorse‐radish peroxidase was found to strongly adsorb on the surface of spectrographic graphite with retained catalytic activity. Efficient electron transfer from the graphite to the oxidized form of adsorbed peroxidase could be achieved without the deliberate addition of a mediator. The peroxidase‐modified graphite was used as a sensor for hydrogen peroxide in a flow‐injection system. Response currents to hydrogen peroxide start at +600 mV vs. SCE and reach a maximal value at −200 mV. Highest activities were found between pH 4 and 6. Linear calibration curves for hydrogen peroxide were obtained from 0.1 to 500 μM with an injection volume of 50 μL.
Anodic oxidation of mercury in the presence of monocyclic ligands in propylene carbonate
Authors: Boudon C. , Gisselbrecht J. P. , Gross M. , Hosseini M. W. 
Published: February 2006

AbstractA series of 12 macrocycles containing 4, 6, or 8 N, S, and O heteroatoms (with increasing size from 14 to 24 atoms in the cycle) was studied to ascertain size and heteroatoms effects on the formation and 14 redox characteristics of their mercuric complexes. The concentration dependence of anodic currents at mercury electrodes in solutions of these ligands led to the determination of the formation constants of the complexes generated according to the folling of

In propylene carbonate, the resulting mercuric complexes were stable (log Ks up to 40) mono‐ and dinuclear species. Their stability depends both on the nature of the heteroatoms and on the size of the macrocycle. For identical ligand sizes, the stability sequence N > S > O was established for mercuric complexes.
Some solvents and supporting electrolytes studied for electrochemical measurement at liquid/liquid interface
Authors: Sun Zhisheng , Wang Erkang 
Published: February 2006

AbstractSolvents used as the organic phase of electrochemical measurement at liquid‐liquid interfaces, including phenyl isothiocyanate, o‐dichlorobenzene, benzyl cyanide, propiophenone, methyl cyclohexanone, cyclohexanone, and methyl amyl ketone, have been studied. Mixing solvents of different polarities in different ratios gives a number of new solvent systems that are suitable for showing a useful “potential window,” including the mixed‐solvent systems with nitrobenzene plus phenyl isothiocyanate, nitrobenzene plus o‐dichlorobenzene, nitrobenzene plus ketones, and the mixed solvent without nitrobenzene, such as phenyl isothiocyanate plus benzyl cyanide, phenyl isothiocyanate plus benzonitrile, o‐dichlobenzene plus benzyl cyanide, and chlorobenzene plus benzonitrile. Supporting electrolytes such as cetylpyridinium tetraphenylborate, ethyl violet tetraphenylborate, and triheptyl dodecylammonium tetraphenylborate are also introduced as the organic phase in order to extend the potential range in the negative direction.
Electrochemical analysis of oxygen content in samples of whole human saliva
Authors: Cohen Florence , Burdairon Gerald , Rouelle François , Chemla Marius 
Published: February 2006

AbstractAlthough dissolved oxygen plays an important role in chemical and biochemical processes in oral medium, no quantitative result exists concerning its concentration in saliva. Using a micro‐computer operated polarographic device, we could measure the two consecutive waves of O2 reduction in whole human saliva samples. After correction of the charging current contribution, we have found that the oxygen concentration is quite low, most often less than 0.08 p.p.m. In order to explain this unexpected result, a study of oxygen consumption by enzymatic reactions in saliva has been undertaken. We could demonstrate that enzymatic reactions of glucose oxidase and catalase are responsible for the complete consumption of oxygen in whole saliva samples.