bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalytic‐adsorptive stripping voltammetric determination of chromium in environmental materials
Authors: Gao Zhiqiang , Siow Kok Siong 
Published: May 2005

AbstractTrace levels of chromium in natural water, soil and plants can be determined directly after accumulation of the chromium(III)‐2,2‐bipyridine complex on a hanging mercury drop electrode, coupled with the catalytic effect of the adsorbed complex on the reduction of nitrite. The adsorptive‐catalytic characteristic of the complex provides the needed sensitivity and selectivity for direct determination of ultratrace concentrations of chromium in environmental samples. The effect of various experimental parameters on the catalytic current was investigated. Under optimal conditions, the adsorptive‐catalytic stripping voltammetric procedure produces a detection limit of 20 pM (1.0 ppt) chromium and a linear catalytic current‐chromium concentration relationship up to 50 nM, following 5 s of accumulation. Most of the coexisting metals do not interfere with the measurements.
Characterization of tyrosinase‐teflon/graphite composite electrodes for the determination of catechol in environmental analysis
Authors: Puig David , Ruzgas Tautgirdas , Emnéus Jenny , Gorton Lo , Marko‐Varga György , Barceló Damia 
Published: May 2005

AbstractAmperometric biosensors incorporating tyrosinase into Teflon/graphite composite were developed for the detection of catechol. The homogeneity of Teflon/graphite was elucidated by means of chronoamperometry (using ferricyanide) and the calculation of the electrochemically active and total surface area of the electrodes. The homogeneity of composite is increased when working with the frozen Teflon. The mechanical strength, sensitivity, apparent Michaelis‐Menten constant, maximum currents, and the compatibility with methanol and acetonitrile of the bioelectrodes were investigated. It was found that 10–30% of graphite in Teflon were suitable for the preparation of electrodes of high mechanical strength and low electrical resistivity. The sensitivity was found to be dependent on the ratio of Teflon/graphite where higher percentage of graphite gave the highest sensitivity. Electrode responses for catechol decreased 5% during one hour of its operation in buffer solution containing 10% methanol.
Regression by least median squares in the calculation of transition times for calibration in chronopotentiometry
Authors: Ortiz María C. , Palacios Jesús López , Sarabia Luis A. , Piangerelli Maria G. , Cingolani Deborah 
Published: May 2005

AbstractThe ability of the least median squares (LMS) method in detection of several straight segments in experimental continuous curves is tested using chronopotentiometric data. As a common experimental system, the chronopotentiometric reduction of Fe(CN)on a Pt electrode is used for this purpose. LMS allows for the correct estimation of transition times and then, for the calibration of the system. LS calibration without outliers detected by LMS assures a better prediction and therefore better calibration quality, because the standard error of estimation is 32.43% less than one obtained with the whole data.
A PVC‐based benzo‐15‐crown‐5 membrane sensor for cadmium
Authors: Srivastava Suresh K. , Gupta Vinod K. , Jain Suresh 
Published: May 2005

AbstractA plasticized poly (vinyl chloride) (PVC)‐based membrane of benzo‐l5‐crown‐5 exhibits a good response for Cd2+ in a wide concentration range (3.16 × 105−1.00 × 10−1M) with a slope of 20mV per decade of [Cd2−]. The response time of the membrane sensor is < 30 s and the same can be used in a pH range 3.8 to 7.0. The electrode has been used, at one stretch, for a period of two months and displays good selectivity for Cd2+ over alkali, alkaline earth and transition metal ions. The membrane sensor has also been used as an indicator electrode in potentiometric titration involving cadmium(II) ions.
Rapid calibration‐free determination of lead in microliter amounts of whole blood
Authors: Jagner Daniel , Ma Feng , Wang Yudong 
Published: May 2005

AbstractA calibration‐free method using portable instrumentation and thus suitable for field screening of lead in whole blood is described. Whole blood (2.5 μL) is diluted first with distilled water (5.0 μL) and then with a matrix‐modifying solution (17.5 μL) containing 0.50M HCl, 600 mg/L HgII, 5% v./v. Triton X‐100 and l00 μg/L of cadmium(II), the latter being used for performance check. A 12 μL subsample is then electrolyzed for 2 min. on a vibrating glassy carbon electrode whereby 90% of the lead(II) ions are reduced to amalgamated lead. Stripping oxidation is then performed with a constant current of 40μA. In two consecutive stripping oxidations the chemical contribution (chemical current) to the oxidation is determined facilitating calculation of the total amount of lead(II) in the sample using Coulombs law subsequent to correction for nonquantitative electrolysis. Results obtained on analysis of certified blood standards deviated less than 14 μg/L on the 3 sigma level in the concentration range 22–118 μg/L and by less than 13% on the 3 sigma level in the range 220–616 μg/L.
Controlled incorporation of heavy metals from aqueous solutions and their electrorelease using composite polypyrrole films
Authors: Hepel Maria , Dentrone Laura 
Published: May 2005

AbstractComposite polypyrrole/catechol films with cation‐exchange properties have been prepared by electropolymerization on AT‐cut 10 MHz gold piezoelectrodes at constant potential. The use of the electrochemical quartz crystal microbalance allowed us to diagnose the type of ion dynamics in these films. Incorporation of a variety of heavy metals was feasible by applying potentials more negative than −200mV (vs. SCE). Regeneration of these films was performed by releasing these metals into the solution during the reverse potential step. Incorporation of the following metal ions PbII, CdII, CoII, and NiII into polymer matrix was found even in the presence of large excess of sodium ions.
Electrochemical and electroreflectance spectroscopic study of copper tetrakis(n‐butoxy carbonyl)phthalocyanine
Authors: Shim Yoon‐Bo , Jin Chang‐Soo , Feng Zhi‐Qiang , Niki Katsumi 
Published: May 2005

AbstractElectrochemical and in‐situ spectroelectrochemical behavior of copper tetrakis(n‐butoxy carbonyl) phthalocyanine (tbcCuPc) was studied using a pyrolytic graphite electrode (PGE). Cyclic voltammogram (CV) shows two consecutive one‐electron redox peaks appearing at ‐670 mV / −640 mV and −770 mV / −710 mV (vs. Ag/AgCl). The reduction processes of tbcCuPc on PGE involved only the ligand. The formal potentials of the adsorbed species determined by UV‐vis electroreflectance (ER) voltammetry were −650 mV and −760 mV (vs. Ag / AgCl electrode). The major peak in the ER spectrum of tbcCuPc appearing near 600 nm was obtained at −760 mV. The peak potential of tbcCuPc‐adsorbed electrode, as observed by ER voltammogram at 600 nm, changed linearly with pH values between 1 and 13. The heterogeneous rate constant, ks, of the electrode reaction of tbcCuPc adsorbed on the PGE surface was determined to be 8.78 × 102 s −1 by analyzing the frequency dependance of the ER signals.
Low temperature spectroelectrochemistry for the characterization of highly reduced σ‐alkyl iron halogenated porphyrins
Authors: Gueutin Claire , Lexa Doris 
Published: May 2005

AbstractLow temperature spectroelectrochemistry was performed to generate highly reduced σ‐alkyl iron porphyrins, which were unstable at room temperature and oxygen sensitive. Suitable conditions for obtaining a stable compound were provided by keeping the thin‐layer cell under strictly anaerobic conditions. To calibrate the cell and check the deoxygenation the electrochemically produced radical anion of ZnTPP was used as an oxygen probe. By satisfying the anaerobic conditions, mainly due to the fact that no Teflon or Kel F spacers were used, it was possible for the first time to generate and characterize highly reduced σ‐alkyl iron porphyrins at low temperatures. The ligation reactions of these species were also stabilized.
Linear and cyclic sweep voltammetry at a rotating disk electrode. A digital simulation
Authors: Strutwolf Jörg , Schoeller Wolfgang W. 
Published: May 2005

AbstractThe transport equation for the rotating disk electrode is solved numerically with appropriate boundary conditions for reversible and nonreversible redox reactions. A comparison of the computational mode with experimentel data is presented. The adaption of a steady state under variations of experimental parameters ν (scan rate) and ω (angular frequency of rotation) is investigated. It is shown that a triangular voltage scan can be used to indicate the attainment of a steady state in every zone of the current‐voltage curve.
Simultaneous determination of chloride and fluoride ions in waters by sequential injection analysis
Authors: Alpízar Jesús , Crespí Antonio , Cladera Andreu , Forteza Rafael , Cerdà Víctor 
Published: May 2005

AbstractA sequential flow injection method for simultaneous chloride and fluoride determination in waters with potentiometric detection is described. The method is based on the simultaneous chloride and fluoride potentiometric detection using two ion selective electrodes in two serial flow‐through cells. The necessary ionic strength adjustment is obtained by mixing the TISAB solution with the sample by diffusion during the propelling process to the detection cells. The new method was applied successfully to drinking water samples.
Electrochemical determination of nitrites in natural waters with ultramicroelectrodes
Authors: Silva S. M. , Alves C. R. , Muchado S. A. S. , Mazo L. H. , Avaca L. A. 
Published: May 2005

AbstractThis work reports the application of carbon‐fiber and gold ultramicroelectrodes for the determination of nitrites in different media. The linear‐sweep voltammetric response for nitrite oxidation on carbon fiber and gold was investigated in the anodic potential range up to 1.6 V (vs. the saturated calomel electrode). The experiments were performed in sulfate solutions, pure and natural waters. Natural water samples were obtained from a commercially available mineral water and from a heavily polluted urban creek. Very well‐defined waves were always obtained showing a half‐wave potential near to the value previously reported for NO oxidation. It was demonstrated that neither O2, or NO exert any influence in the nitrite oxidation response. The detection limits calculated were within the range of 2.6 to 9.7 μM, the highest being associated to the polluted water sample on carbon fiber and the lowest to mineral water on gold ultramicroelectrodes.
Potentiometric determination of L‐dopa, carbidopa, methyldopa and aspartame using a new trinitrobenzenesulfonate selective electrode
Authors: Badawy S. S. , Issa Y. M. , Tag‐Eldin A. S. 
Published: May 2005

AbstractA selective PVC membrane electrode based on the ion‐pair of cetylpyridinium (CP+) and 2,4,6‐trinitrobenzenesulfonate (TNBS−) as the electroactive species was developed. The electrode exhibits a rapid and Nernstian response to TNBS− from 5.0 × 10−5 to 1.0 × 10−2M at 25 ± 0.1°C. The response is unaffected by the change of pH over the range 2–12. Selectivity coefficients for a larger number of organic and inorganic anions and sugars are given. The electrode has been successfully applied to the determination of L‐dopa, carbidopa, methyldopa and aspartame in pure solutions and in their pharmaceutical formulations with a precision and accuracy of 0.9–1.3% without interference from excipients.
The standard potentials of the electrode “dissolved atomic mercury/dissolved mercury ions”
Authors: Scholz Fritz , Lovrić Milivoj 
Published: May 2005

AbstractThe standard potentials of the redox electrodes “dissolved atomic mercury/dissolved mercury ions” are calculated to be E0(Hg0/Hg2+) = 0.661 V (vs. SHE and E0/Hg0 Hg) = 0.410V (vs. SHE). The standard potential of the electrode “metallic mercury/dissolved mercury ions” E0(Hg/Hg2+) = 0.8535V (vs. SHE) is the formal potential of the electrode “dissolved atomic mercury/dissolved mercury ions” at saturation activity of atomic mercury. In all calculations involving dissolved atomic mercury below saturation activity, the standard potentials E0(Hg0/Hg2+) and E0(Hg0/Hg22+) have to be used or the relation between them and E0(Hg/Hg2+) and E0(Hg/Hg) has to be taken into account.
A novel approach to the solid‐state electrochemistry of fullerenes: Cyclic voltammetry at a C‐modified graphite‐PTFE composite electrode
Authors: Kutner Włodzimierz 
Published: May 2005

AbstractA Buckminsterfullerene (C60)‐modified graphite‐PTFE composite electrode was prepared by pelletizing a powder mixture of 10% C60, 30% graphite, and 60 % PTFE (by weight). Multicyclic voltammetry of the electrode in acetonitrile solution of tetra‐n‐butylammonium perchlorate shows reproducible, two‐step, C60 charging and discharging, in the potential range for which only the first two, i.e., C and C electroreductions occur. This behavior favorably compares to that reported earlier for the C60 solid films, in the same solution. The composite electrode is recommended as a convenient tool for investigation of the solid‐state electrochemistry of fullerenes.
Immobilization of pyrroloquinoline quinone on gold by carbodiimide coupling to adsorbed polyamines: Stability comparison to attachment via a chemisorbed thiol monolayer
Authors: Moore Andrew N. J. , Katz Eugenii , Willner Itamar 
Published: May 2005

AbstractPyrroloquinoline quinone (PQQ) was immobilized on gold electrodes by prior adsorption of the polyamines polyethylenimine, and triethylene tetraamine, followed by carbodiimide coupling of PQQ to the surface‐adsorbed amine groups. The stability and electrochemical behavior of the electrodes, in which the amino‐containing linker molecule is adsorbed on the electrode surface, were compared with those of electrodes prepared by carbodiimide coupling of PQQ to a cystamine monolayer, in which the sulfur‐containing linker molecule is associated with the gold surface. The electrodes prepared using adsorbed polyethylenimine showed comparable stability to those based on a cystamine monolayer, but reveal enhanced stability to application of negative potentials (< −1.1 V). The method provides an alternative to the conventional functionalization of Au electrodes by thiols.
Renewable, reagentless glucose sensor based on a redox modified enzyme and carbon‐silica composite
Authors: Sampath Srinivasan , Lev Ovadia 
Published: May 2005

AbstractA new type of sol‐gel derived, ferrocene derivatized glucose oxidase based amperometric biosensor is introduced. The electrode consists of graphite powder impregnated with a ferrocene modified enzyme imbedded in an organically modified silicate network. In this assembly, graphite powder provides percolation conductivity, the organic modification of the silicate ensures that the whole bulk of the material is not wetted by the analyte, thus providing a thin reactive layer. The ferrocene which is covalently attached to the enzyme acts as a mediator for the enzymatic reaction, thereby communicating with the conducting graphite in the matrix. The electrode can be reproducibly renewed by mechanical polishing. Thick film biosensors, where a drop of the analyte is sufficient for the sensing process is also demonstrated with this material.
Enhanced selectivity and sensitivity of first‐generation enzyme electrodes based on the coupling of rhodinized carbon paste transducers and permselective poly(o‐phenylenediamine) coatings
Authors: Wang Joseph , Chen Liang , Liu Jie , Lu Fang 
Published: May 2005

AbstractHighly specific oxidase‐based amperometric biosensors, based on the coupling of anti‐interference layers with selective metal‐dispersed carbon transducers are described. In particular, the efficient and preferential electrocatalytic action of rhodinized carbon pastes towards the peroxide product is combined with the discriminative properties of poly(o‐phenylenediamine) (PPD) films. Such focus on both the transducer and recognition layer offers freedom from interferences, while resulting in higher sensitivity towards the substrate. The influence of preparation parameters is explored, and the surface microstructures are discussed. Similar improvements are reported for the electrodeposition of rhodium, PPD and glucose oxidase onto glassy carbon transducers.
Fast amperometric immunoassay for hantavirus infection
Authors: Krishnan Rajesh , Ghindilis Andrey L. , Atanasov Plamen , Wilkins Ebtisam , Montoya Jim , Koster Frederick T. 
Published: May 2005

AbstractThe determination of specific antibodies against Hantavirus in blood plasma has been developed. The assay technique is based on a flow through amperometric immunoelectrode. Highly dispersed carbon material serves as an immunosorbent and at the same time as an electrode material. The analysis employed the ‘sandwich’ assay scheme. Recombinant protein of Hantavirus was immobilized on the surface of the immunosorbent. Target analyte captured by the immunosorbent at the first stage of incubation interacts with the peroxidase labeled antihuman antibodies at the second stage of incubation. The detection of peroxidase label was conducted amperometrically by electroreduction of iodine formed as a product of peroxidase catalyzed reaction. The technique permits determination of specific antibodies against Hantavirus in blood plasma using a 22 min assay time.
The effect of organic solvent properties on a catalase enzyme sensor for monitoring hydrogen peroxide in nonaqueous solutions
Authors: Campanella Luigi , Martini Umberto , Sammartino Maria P. , Tomassetti Mauro 
Published: May 2005

AbstractA catalase based biosensor for determining hydrogen peroxide in organic solvents, operating directly in nonaqueous solutions, was prepared, characterized (using water saturated chloroform as solvent) and applied in comparative tests using four different anhydrous organic solvents in order to determine their effect on biosensor sensitivity and thus on enzymatic activity in different organic solvents. Results are discussed in terms of log P and dielectric constant (DEC) values of the solvents considered.
Amperometric sulfur dioxide sensors using the gold deposited gas‐diffusion electrode
Authors: Chiou Chiou‐Yen , Chou Tse‐Chuan 
Published: May 2005

AbstractA dispersed catalyst gas‐diffusion electrode for SO2 sensors has been developed. The particle size of the catalyst electrode was obtained. A three‐electrode potentiostat was used to test the sensing electrode at an optimal constant potential. When the SO2 diffuses through the porous electrode, the electrochemical oxidation of SO2 takes place at the active gold sites. The results indicated that the SO2 sensor was stable and the response time was fast. The sensitivity of the developed SO2 sensor was l.002μAcm−2ppm−1, and its performance was good.
D‐Fructose sensing electrode based on electron transfer of D‐fructose dehydrogenase at colloidal gold‐enzyme modified electrode
Authors: Yabuki Soichi , Mizutani Fumio 
Published: May 2005

AbstractA complex of colloidal gold (Au) particles and D‐fructose dehydrogenase was prepared. A glassy carbon (GC) electrode was modified with the complex. The anodic current response to D‐fructose was measured by using the GC electrode modified with the complex at +0.5 V (vs. Ag/AgCl). Response time was within 15 s. No current response was observed in the absence of enzyme, so that the increased oxidation current was confirmed to be caused by the electron transfer from enzyme to electrode. Linear response range of the electrode was up to 0.5 mM fructose concentration. Fructose concentrations of soft drinks which were determined using the electrode agreed well with the results of the F‐kit.
A polarographic and voltammetric study of the copper‐phenazopyridine monohydrochloride system in phosphate buffer medium
Authors: Çakir Osman , Biçer Ender 
Published: May 2005

AbstractThe electrochemical behavior of copper complexed with phenazopyridine monohydrochloride (2.6‐diamino 3‐phenylazo‐pyridine monohydrochloride, pyridium) has been studied in 0.1 M phosphate buffer (pH 6.0). It was observed that CuII ions in the presence of pyridium are reduced at the mercury electrode in two distinct stages; this is a consequence of the interaction of pyridium with CuI ions. Tests showed that pyridium forms stable complexes with CuI and CuII ions. However, it was found that pyridium formed a 1 : 1 complex with CuII and a 1 : 2 complex with CuII ions.
Adsorption and detection of peptide nucleic acids at carbon paste eletrodes
Authors: Wang Jpseph , Rivas Gustavo , Cai Xiaohua , Chicharro Manuel , Dontha Narasaiah , Luo Denbai , Palecek Emil , Nielsen Pater E. 
Published: May 2005

AbstractPeptide nucleic acids (PNA) are new DNA analogs which offer great promise for highly specific DNA biosensors, for use as antisense drugs, or for various molecuilar biology applications. This article evaluates the interfacial behavior of PNA at carbon paste electrodes, in comparison to DNA. While both PNA oligomers display a strong adsorption onto the carbon surface, they differ intheir interfacial properties due to differences in change and structure. Factors influencing the adsorption behavior, including the adsorption potential or time, PNA concentration, coexisting anions and cations, or buffer concentration, are explored. The strong adsorption is exploited for an effective preconcentration step prior to the chronopotentiometric measurement. The resulting adsorptive stripping potentiometric protocol offers convenient quantitation of ng/mL levels of PNA, as desired for future diagnostic, pharmaceutical and biological applications of these DNA analogs.
Highly sensitive heavy metal analysis on platinum‐ and gold‐ultramicroelectrode arrays
Authors: Uhlig Albrecht , Schnakemberg Uwe , Hintsche Rainer 
Published: May 2005

AbstractThe use of platinum‐and gold‐ultramicroelectrode arrays for heavy metal analysis is described. The noble metal microelectrodes are structured with standard silicon technologies. The geometry of the electrode array is varied and optimized in regard to the microelectrode characteristic. Mercury film formation and–dissolution on platinum microelectrode arrays is characterized and compared with iridium electrodes of the same geometry. Gold microelectrode arrays are shown to be useful for mercury detection. The repeated use of the sensors has been studied. Optimizing the electrode gemoetry and the stripping procedure results in detection limits down to the ng/L range.
In situ monitoring of peroxodisulfate anion production
Authors: Dalrymple Ian M. , Hitchman Michael L. , Price Denis , Millington J. Peter 
Published: May 2005

AbstractA direct, continuous method for the measurement of peroxodisulfate anion has been devised and assessed. The approach is based upon the reduction of the anion under mass transfer limiting conditions at an amalgamated copper rotating disk electrode. The preparation of the disk electrode by Hg electroplating was examined in detail in order to generate a reproducible surface. The system was calibrated by demonstrating that the limiting current density for peroxodisulfate reduction was directly proportional to its bulk solution concentration. An electrochemical cell arrangement was then developed to permit the continuous, in situ measurement of peroxodisulfate concentration during electrochemical synthesis.