bluuebunny/crossref_metadata_2025 huggingface dataset:
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

A 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

The 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

The 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

A 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

Both 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

Various 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

An 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

A 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

The 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

Significant 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

The 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

The 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

Polarographic 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

Horse‐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

A 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

Solvents 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

Although 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.
Kinetically controlled urease electrode
Authors: Hamann H. , Scheller F. , Kühn M.
Published: February 2006

The 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

Poly‐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

The 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

The 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

A 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

An 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

The 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

The 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

The 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

The 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

A 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

The 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

A 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

Recently, 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

Seven 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

Flow‐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

A 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

The 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

Bolton‐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

The 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

Ultramicroelectrodes 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

Battery‐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

Cyclic 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

An 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

The 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

Flexible 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.
Characterization of poly(ester‐sulfonic acid)‐coated microvoltammetric electrodes
Authors: Wang Joseph , Lin Meng Shan
Published: February 2006

Coating microvoltammetric electrodes with a poly(ester‐sulfonic acid) film offers substantial improvements in their selectivity toward cationic neurotransmitters. This charged film tends to exclude anionic interferences, such as ascorbic acid or anionic biogenic amine metabolites. The temporal response of polyester‐ionomer‐coated microelectrodes is evaluated under dynamic flow‐injection conditions. Chro‐noamperometry and cyclic voltammetry are used to explore the discriminative properties of these microelectrodes under quiescent conditions. The attractive permselective, ion‐exchange, antifouling, and dynamic properties of the polyester ionomer, coupled with its low cost and strong adherence to surfaces, could be very valuable for in vivo brain electrochemistry.
Measurement of peroxide in oils by controlled‐potential coulometry using a vapor‐grown carbon fiber electrode
Authors: Uchiyama Shunichi , Shimamoto Miwa , Suzuki Shuichi , Hamamoto Osamu
Published: February 2006

A small amount of a linoleic acid sample solution was dropped on a carbon fiber paste containing a mixture of acetic acid and methanol (1:1) saturated with potassium iodide. The present method needs no titration, and the only pretreatment needed for the sample is the dissolution of linoleic acid with an acetic acid—chloroform mixture (3:2). The complete electrolysis time of iodine produced by the reaction of iodide ion and peroxides was found to be 2–3 minutes. The results obtained by coulometry were in fairly good agreement with those obtained by conventional iodometry.
Evaluation of electrodes coated with metal hexacyanoferrate as amperometric sensors for nonelectroactive cations in flow systems
Authors: Thomsen Karsten N. , Baldwin Richard P.
Published: February 2006

Two electrodes modified with either nickel or cupric hexacyanoferrate films were evaluated and compared as sensors for nonelectroactive cations in a flow‐injection system. Both gave responses for group 1A and ammonium ions, but only the electrode modified with cupric hexacyanoferrate was sufficiently stable for use in flowing solutions. This electrode responded to K+, NH, Rb+, and Cs+ ions rather selectively. Within this group, the selectivity could be controlled from general to almost specific toward Cs+ by the potential at which the electrode was poised. The electrode was compatible with a mobile phase of dilute nitric acid commonly used in ion chromatography, and chromatographic detection limits of 2 × 10−7 M and linear responses over two decades were obtained. The electrode was applied to the ion chromatographic analysis of K+ and NH in urine and K+ in blood serum samples.
Electrochemical reduction of loprazolam mesilate in an aqueous medium
Authors: Arcos J. , El Jammal A. , Viré J.‐C. , Patriarche G. J. , Christian G. D.
Published: February 2006

The electrochemical characteristics of loprazolam mesilate have been evaluated in an aqueous solution using dc, ac, and normal and inverse pulse polarography, as well as cyclic voltammetry and controlled‐potential coulometry. This drug undergoes three different reduction steps. The first, a four‐electron transfer, corresponds to the reduction of the nitro group to give the corresponding hydroxylamine. The second, a two‐electron transfer, corresponds to the reduction of the azomethine group, either before or after (in an acidic solution) hydrolysis. The third wave corresponds to a four‐electron transfer in an acidic medium and to a two‐electron transfer in an alkaline medium. In an acidic solution, this third step involves the two‐electron reduction of the hydroxylamine group to the corresponding amine plus the two‐electron reduction of the double bond between N‐methylpiperazine and the imidazol group. In an alkaline solution, only the latter reduction takes place. Such behavior holds promise for analytical measurements of the drug.
Cathodic stripping analysis of DNA/RNA bases in nonaqueous media
Authors: Fish Judith R. , Ciszewski Aleksander , Malinski Tadeusz
Published: February 2006

The methods for the determination of nucleic acid bases by differential pulse cathodic stripping voltammetry in dimethyl sulfoxide are proposed and developed. One method uses mercury drop or film electrodes. The required anion is produced by the deprotonation of the parent molecule by added tetrabutyl‐ammonium hydroxide (TBAOH). Optimization of the method is discussed. The effects of deposition potential or time, scan rate, pulse height, TBAOH concentration, and other experimental parameters are examined. Included are the results of the determinations of thymine, uracil, cytosine, adenine, and guanine. The second method uses a mercury‐film rotating ring‐disk electrode. The anion, produced electrochemically at the disk held at a negative potential, is swept to the ring and deposited at a suitable, more positive potential. Detection limis for nucleic acid bases are 10−8 to 10−9 M.
Flow‐injection analysis of hydrogen peroxide using a horseradish peroxidase‐modified electrode detection system
Authors: Sánchez Pilar Dominguez , Blanco Paulino Tuñón , Alvarez José Maria Fernández , Smyth Malcolm R. , O'Kennedy Richard
Published: February 2006

A flow‐injection analysis (FIA) system utilizing a horseradish peroxidase‐modified amperometric electrode is described. The enzyme was immobilized through adsorption onto a glassy carbon electrode, and the system is used to determine hydrogen peroxide at submicromolar levels. The response is based on the enzymatic reduction of hydrogen peroxide in the presence of hydroquinone acting as an electron mediator. The oxidized quinone produced in the enzymatic reaction is reduced at the electrode, and the reduction current was found to be proportional to the concentration of hydrogen peroxide. Calibration curves were found to be linear between 2.5 × 10−8 and 1.0 × 10−6 M, and the method has a detection limit of 1.0 × 10−8 M.
Application of partial least‐squares regression for signal resolution in differential pulse anodic stripping voltammetry of thallium and lead
Authors: Henrion André , Henrion René , Henrion Günter , Scholz Fritz
Published: February 2006

This work addresses the problem of signal resolution by partial least‐squares regression (PLS) for differential pulse stripping voltammograms. The performance of PLS is demonstrated for an example of calibration with mixtures of two analytes (Tl+and Pb2+) with strongly overlapping voltammograms. The accuracy of the determination of concentrations for validation mixtures was found to be considerably higher with PLS than with simple evaluation using currents observed at two potentials (requiring resolution of a system of two linear equations with two unknowns). Hence, PLS is recommended for computer‐assisted, on‐line voltammetric analysis of multicomponent systems.
Influence of the adsorption of organic compounds on submonoleyer stripping voltammetry of metals at solid electrodes
Authors: Hepel Maria
Published: February 2006

The effect of the adsorption of foreign organic compounds on the stripping voltammetry of metal adatoms deposited in submonolayer amounts at solid electrodes has been analyzed. It is shown that, for irreversible metal deposition processes, the adatom deposition current and, at a constant deposition time, the deposition charge are sensitive to the presence of the adsorbed foreign species on the electrode surface. Equations describing the dependence of the metal adatom deposition charge and the stripping peak current on the deposition potential, deposition time, concentration, and lateral exchange interactions between metal adatoms and adsorbed molecules have been derived. In the case of negligible exchange interactions, the peak current for adatom probe desorption decreases linearly with the surface coverage by foreign adsorbate. Direct evaluation of the kind and strength of exchange interactions is possible because the expression derived for the metal adatom desorption peak potential was used. It was found that the shift of the peak potential to more positive potentials is due to the lateral attraction exchange interactions, while the shift to more negative potentials was caused by the exchange repulsion interactions. No shift in the peak potential occurred in the absence of exchange interactions irrespective of the adatom surface coverage after the deposition step.
Differential pulse polarography of buspirone
Authors: Squella J. A. , Borges Y. , Bobadilla L. , Nuñez‐Vergara L. J.
Published: February 2006

A new differential pulse polarographic method for the determination of buspirone pharmaceutical formulations is proposed. The method is based on the CN bond electroactivity of buspirone pirimidinic ring. Recovery study and content uniformity test are described. Adequate precision and accuracy were obtained. Sample preparation is easy, and no excipient separation is required.
Voltammetry of germanium telluride
Authors: Reddy K. V. Sridhar , Reddy S. Jayarama
Published: February 2006

The voltammetric behavior of semiconductor grade germanium telluride was studied by ac and differential pulse polarography. The electrochemical behavior and analytical procedures for the simultaneous estimation of germanium and tellurium in germanium telluride are discussed. The kinetic parameters of the electrode process are evaluated.
Electrochemical analysis for environmental control
Authors: Kalvoda R.
Published: February 2006

Electroanalysis is widely used for environmental monitoring. This review summarizes the most progressive electroanalytical methods and the development of novel sensors that are the primary part of monitors and analyzers for environmental purposes. The utility of voltammetry, pentiometry, conductometry, and coulometry for environmental monitoring is surveyed and 64 references are provided.