bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polypyrrole‐based amperometric biosensor for sulfite determination
Authors: Adeloju S. B. , Shaw S. J. , Wallace G. G. 
Published: May 2005

AbstractAn amperometric biosensor for sulfite determination, based on the incorporation of sulfite oxidasen (SOD) into a polypyrrole film by galvanostatic formation, has been successfully developed. The use of the biosensor involves the application of a constant potential of –700 mV, which promotes oxgen reduction as the predominant reaction. The optimum analytical conditions for the biosensor were 0.1 M phosphate buffer with 0.5 M KC1. pH 7.0, and a platinum disk electrode. The response of the biosensor to sulfite was linear from 0 to 80 mg/L, and the minimum detectable amount was found to be 5 mg/L. Usual interferants in sulfite determination such as ascorbic acid, sodium nitrite, and sodium sulfate did not interfere with the biosensor. The excellent resproducibility of the sulfite response with 4 hours of repeated use provides the basis for the construction of a disposable or renewable biosensor for sulfite determination.
Simultaneous determination of copper, lead, cadmium, and zinc in previously lyophilized biological tissues using flow‐injection analysis/anodic stripping voltammetry
Authors: Izquierdo A , de Castro M. D. Luque , Valcárcel M. 
Published: May 2005

AbstractImprovements in three main aspects of the analysis of metal traces in biological tissues are proposed, namely: (a) lyophilization of the samples both to preserve them and to favor the digestion process; (b) digestion of the lyophilized tissues using an effective and fast procedure; and (c) automatic determination of the target analytes by flow‐injection analysis/anodic stripping voltammetry (FIA/ASV). After optimization of these steps, the overall procedure was successfully applied to the simultaneous determination of copper, lead, cadmium, and zinc in certified reference materials (CRMs) and fresh bovine liver samples with good results. Finally, the performance of the method was validated by a statistical study using parameters of the certification campaign of the CRMs; the results obtained being within, or close to, the confidence levels of the certification campaign.
A biosensor for L‐amino acids using polytyramine for enzyme immobilization
Authors: Cooper Julia C. , Schuber Florian 
Published: May 2005

AbstractElectrodeposition of polytyramine is demonstrated to be a simple and convenient procedure for electrode modification, generating amine groups to which L‐amino acid oxides can be covalently bound. An L‐amind acid oxidase (L‐AAOD)‐polytyramine electrode can be used for detection of L amino acids, via the current due to oxidation of enzymatically produced hydrogen peroxide. The calibration graph of the sensor for phenylalanine is linear up to 1.4 mM with a lower limit of detection of 0.07 mM. The useful measuring range for leucine is between 0.07 and 3 mM. The enzyme‐polytyramine electrodes are stable for more than 1 month. The polymer coating affords some protection of the elearode from direct (nonenzymic) oxidation of electroctive amino acids, which may otherwise cause elecatrode fouling, although at present, the polymer selectivity is insufficient to prevent errors in estimation of analyte concentration.
Electrochemical characterization of a novel organic electrolyte gel
Authors: Nahir Tal M. , Qiu Yong‐Jian , Williams Joel L. 
Published: May 2005

AbstractThe fabrication and electrochemical characterization of a variety of self‐supported thermorevrsible organic electrolyte gels prepared using l,3:2,4‐dibenzylidene sorbitol (DBS) as a gelling agent are reported. Impedance analysis and cyclic voltammetry were used to examine these gel systems, which exhibit ionic conductivities similar to corresponding liquid electrolyte solutions.
Amperometric glucose sensor containing nondiffusional osmium redox centers: Analysis of organic‐phase responses
Authors: Iwuoha Emmanuel I. , Smyth Malcolm R. , Vos Johannes G. 
Published: May 2005

AbstractGlucose oxidase (GOx) electrodes were constructed by complexing GOx with the redox osmium macromolecule, [Os(bpy)2(PVP)20Cl]Cl (abbreviated Os‐Polymer). The biosensor produced high catalytic current densities in response to β‐D‐glucose in solvent media that were up to 100% in acetonitrile. The sensor, which functions by relaying electrons between GOx flavin adenine dinucleotide redox sites {GOx(FAD/FADH2)} and the electrode, showed great improvement in its organic‐phase responses in the presence of certain amounts of water. Cyclic voltammograms were analyzed for the elucidation of reaction mechanism and determination of the formal electrode potential (E°′). The electrode potential E°′ decreased as water content of the medium increased. Steady‐state responses of the sensor in CH3CN/H2O mixtures, 1 to 35% v/v in H2O, were observed at 450 mV. The kinetic analysis of the steady‐state amperometric response of the biosensor was based on a rapid charge propagation within the polymer compared to the enzyme kinetics. Maximum steady‐state current density jmax and apparent Michaelis‐Menten constant KM were evaluated from electrochemical Eadie‐Hofstee plots. Our results show that jmax reached an optimal value of 282 μA cm−2 in CH3CN/H2O (80 + 20% v/v). There was no drastic change in KM for the different CH3CN/H2O media. This indicates that CH3CN does not bind to, or act as a cosubstrate for, the immobilized GOx. Effect of water on sensor response in the polar organic solvent has been explained on the basis of its role in increasing the flexibility of the immobilized GOx active site environment.
A study of the differential pulse polarographic and stripping voltammetric behavior of the H+/K+ ATPase inhibitor SK&F 95601 and its degradation products
Authors: McClean S. , Maxwell T. , Ramachandran V. N. , O'Kane E. , Smyth W. F. 
Published: May 2005

AbstractThe differential pulse polarographic (DPP) behavior of SK&F 95601 (I) has been studied I the pH range 0 to 14. At pH ≤ 2, (I) rapidly degrades into the sulfenamide (D) and (D), which are both reduced by 2e− processes, the former being subject to strong reactant adsorption. SK&F 95601 itself is reduced in a 4e process up to pH10, and either pK2 or pK3 values, determined spectrophotometrically, are manifested polarographically at neutral pH. A pK5 value of 9.0 corresponding to the benzimidazole N‐H group deprotonation is manifested polarographically with a pK′5 value of ca. 11. SK&F 95601 and its degradation produce D, degraded D, and D can all be determined by adsorptive stripping voltammetry (AdSV) with limit of detections (LODs) of 10−8 mol dm−3, except for the latter molecule with an LOD of 10−7 mol dm−3. These LODs are superior to those determined by DPP. Mixtures of these molecules can also be resotved with similar LODs. Cd2+ can be determined by ASV with a superior LOD in the presence of (I), i.e 0.08 ppb as compared to 0.57 ppb in its absence, due to chelation phenomena.
The adsorption of 1,4‐dibromobenzene on gold electrodes: A combined in situ infrared and surface‐enhanced raman spectroscopic investigation
Authors: Schomaker Silke , Holze Rudolf 
Published: May 2005

Abstract1,4‐dibromobenzene (DBB) was adsorbed on a polycrystalline gold electrode from aqueous solutions. In situ vibrational infrared (IR) and Raman spectroscopy yielded results implying an edge‐on coordination of the adsorbed molecule. Adsorption does not only involve the ring an system of the molecule, but also its bromide substituents. In comparison to the potential‐modulated in situ IR method, the Raman spectroscopy shows higher sensitivity for adsorbate detection.
Wall‐Jet electrode system for anodic stripping voltammetry
Authors: Omanović D. , Peharec Ž , Magjer T. , Lovrić M. , Branica M. 
Published: May 2005

AbstractA construction of an electroanalytical cell with a wall‐jet electrode (WJE) system consisting of a built‐in centrifugal pump and a thin mercury film‐covered glassy carbon stationary disk working electrode and its application to the differential pulse anodic stripping voltammetric measurements of traces of cadmium and lead are described. Characteristics of the new hydrodynamic electrode system are compared with the properties of the rotating disk electrode (RDE). The new described system yields rather high flow rates (2 to 12 mL/s) exhibiting about a twofold higher accumulation rate than the RDE. It allows shorter deposition time, faster analysis, and lower determination limits of trace metals in water samples. Experimental determination limit for lead ions of 8 × 10−12 M, after accumulation of 7.5 minutes with turbine rotating of 2500 rpm, was obtained.
Ligand‐catalyzed metal ion reduction: Kinetics and analytical applications of nickel reduction catalyzed by nicotinamide
Authors: Bǎnicǎ Florinel‐Gabriel , Doicin Luminiţa‐Irinel , Fodor Alexandrina , Ion Ana 
Published: May 2005

AbstractThe catalytic reduction of Ni (II) in the presence of nicotihamide (NA) at pH < 7 was studied by direct‐current and differential‐pulse polarography (DPP). The prewave (with E1/2 around –0.78 V (versus saturated calomel electrode (SCE)) shows the typical behavior of an electrode process with regeneration of the reactant by a second‐order, rate‐determining chemical reaction. This reaction consists in the formation of the reducible nickel complex. The kinetics of the electrode process was studied by means of an adapted form of the equation derived by Koutecký for electrochemical reactions with a parallel chemical step. The rate constant for the formation of nickel‐nicotinamide complex is slightly dependent en pH and buffer composition and ranges between 4.5 and 6.7 × 103 mole−1 L s−1. This electrode process enables the selective determination of Ni (II) in presence of a large excess of cobalt. For example, nickel impurity in cobalt salts can be determined by DPP, in acetate buffer (pH 4.6) containing 0.01 M nicotinamide and about 0.1 M cobalt salt sample.
An ion‐gate response of a glutathione monolayer assembly highly sensitive to lanthanide ions
Authors: Takehara Kô , Aihara Makoto , Ueda Nami 
Published: May 2005

AbstractThe self‐assembled glutathione (γ‐L‐glutamyl‐L‐cysteinyl‐glycine, GSH) monolayer was formed on a gold electrode via a sulfur attachment of the cysteinyl residue. The effect of lanthanide ions (La3+, Eu3+ and Lu3+) on the ion‐gate behavior of this electrode was studied by using cyclic voltammetry (CV) and Fe(CN)63– as a probe ion. These ions were found to open the ion gate with a few micromoles, and the effect was in the order of La3+ > Eu3+ Lu3+.
The amperometric titration of copper(II) sulfate with potassium permanganate in surfactant suspensions
Authors: Franklin Thomas C. , Nnodimele Remi A. 
Published: May 2005

AbstractIt has been demonstrated that it is possible, in the presence of a cationic surfactant, to oxidize copper(II) sulfate (CuSO4. 5H2O) with potassium permanganate in aqueous sodium hydroxide solutions and to oxidize the solid copper(II) sulfate with solid potassium permanganate in methylene chloride. Presumably the surfacant solubilizes the solids and protects the unusual valence from reaction with water. In both solvents, the rate of reaction was fast enough to be followed with an amperometric titration. The stoichiometric reactions in these solvents were found to involve one potassium permanganate for three copper(II) sulfates, indicating that copper(II) was oxidized to in copper(III) while permanganate was reduced to manganese(IV). The results show that both ions and solids, suspended and coated with surfactants, can react rapidly enough for the reactions to be used in titrations and that copper(III) can be formed by chemical reaction and stabilized by a cationic surfactant film.
Catalytic determination of traces of uranium in rocks by chronocoulometry
Authors: Cantagallo Maria Inês C. , Gutz Ivano G. R. 
Published: May 2005

AbstractThe chronocoulometric method for the determination of trace levels of uranium based on the catalytic reduction of nitrate described in a preceding article, was applied and evaluated with real and synthetic samples Samples with complex matrixes like rocks were first solubilized in h9ot acid (HF+ HNO3) by digestion under pressure in a PTFE bomb. When necessary, liquid‐liquid exraction with tri‐n‐ butyl phosphate (TBP) followed by reversion to aqueous phase was used for previous separation of interferents. Results for a feldspar, a phosphorite, and three granitic rock in the range of 2 to 100 ppm, are in good agreement with those obtained by other tedhniques such as X‐ray fluorescence, isotopic dilution‐mass spectrometry (ID‐MS), and instrumental activation analysis (differences of 4 to 16% in relation to the unweighted mear for different techniques).
A high‐speed computerized polarographic system for cathodic stripping voltammetry in seawater
Authors: Hernández‐Brito J. J. , Cardona‐Castellano P. , Siruela‐Matos V. , Pérez‐Peña J. 
Published: May 2005

AbstractA low‐cost computer‐controlled high‐speed polarographic system has been devised to determine heavy metals in seawater using adsorptive stripping voltammetry. The system consists of a potentiostat that has been developed in our Department, a 303A PAR polarographic cell, a personal computer with an I/O digital board PIO‐96, and a hp7440 plotter. The potentiostat operates between –2.5 and +2.5 V, with a multirange selection current between ±100 nA and ±1000 μA. There are various outlet channels with different time constants and noise levels. The quickest channel can detect processes in a 10 μs range with a noise level of ±4 nA (seawater matrix), while for a range of 30 ms, the noise is ±100 pA. The software controls different signal patterns, techniques, and a complete set of operations and has been developed in the C language to accelerate the data acquisition. The system has been successfully applied to high‐speed cathodic stripping voltammetry (HSCSV) on seawater samples, showing promising results in that there is an increase in the sensitivity over standard methods in the presence of oxygen and in stirred solutions. The analysis time can be reduced significantly at a high speed, and also, determinations aboard a ship are improved.
Ultrasensitive adsorptive–catalytic stripping voltammetry of iron in the presence of hydroxamic acids and hydrogen peroxide
Authors: Lu J. , Wang J. , Yarnitzky C. 
Published: May 2005

AbstractAn ultratrace catalytic–adsorptive stripping voltammetric procedure for the determination of trace amounts of iron is reported. The method is based on the interfacial accumulation of the iron‐N‐benzoyl‐N‐phenylhydroxylamine complex on the hanging mercury drop electrode, followed by catalytic reduction of the adsorbed complex in the presence of hydrogen peroxide. The presence of hydrogen peroxide greatly amplifies the adsorptive stripping response. Optimum experimental conditions have been explored to give an extremely low detection limit of 1.8 × 10−10 M (10 ng/L) iron following 10min accumulation. Analogous improvements are reported for other hydroxamic acid complexes of iron. Such acids hold great promise for developing additional adsorptive stripping procedures.
Differential pulse polarographic investigation of the nickel(II)–orotic acid complex
Authors: Blázquez L. Calvo , Gil E. Pinilla , Carra R. M. García‐Moncó , Misiego A. Sánchez 
Published: May 2005

AbstractDifferential pulse polarographic studies illustrate that the NiII ion forms a complex with orotic acid (aqueous medium, pH = 9.5, ionic strength μ = 0.2). The stiochiometric composition of this complex has been determined, and a method for its determination in an aqueous medium is proposed.
Dual enzyme amperometric biosensor for putrescine with interference suppression
Authors: Yang X. , Rechnitz G. A. 
Published: May 2005

AbstractA putrescine biosensor has been developed. Putrescine oxidase, peroxidase, and bovine serum albumin were cross‐linked directly on the surface of a graphite electrode by glutaraldehyde. The sensor was used to determine putrescine at 0 mV (vs. Ag/AgCl reference electrode) in a potassium phosphate buffer (pH 7.4) solution containing 4 mM dopamine (3‐hydroxytyramine). The response of putrescine was linear up to 600 μM with a standard deviation of 2.8%. The detection limit was 5 μM. The response time was around 30 s. The lifetime was over 30 days when the electrode was used every day. The interferences of cadaverine and spermidine could be eliminated by added dopamine which, apparently, inhibits the enzymatic conversion of these substrates more strongly than that of putrescine.
Kinetic and mechanistic study of the copper(II)–oxamate complexation, monitored by the CuII solid state ion selective electrode
Authors: Karayannis M. I. , Veltsistas P. G. , Merkoci A. X. 
Published: May 2005

AbstractThe complexation process of copper(II) with oxamates was followed by the use of a copper solid state ion selective electrode. The shape of the recorded potential vs. time was interpreted on the basis of the known kinetic expressions for a two step reaction, monitoring the consumption of the reagent. The potential changes of the electrode are attributed to a decrease in the copper concentration. The curves are of an exponential form with two distinct parts, the first due to the intermediate activated complex, which is produced very rapidly, and the second is due to the slow formation of the soluble chelate. The effects of various parameters are studied in relation to the retardation of the first step. The reaction rate constant k, the equilibrium constant K* for the first step, the stability constant K, the activation energy Ea, the change in enthalpy, and the product (pZ) of the frequency and steric factors were determined. On the basis of the above data, a mechanistic scheme for this complexation reaction is proposed.
Cation determination in aqueous solution using the methyl viologen‐doped zeolite‐modified carbon paste electrode
Authors: Walcarius A. , Lumberts L. , Derouane E. G. 
Published: May 2005

AbstractMethyl viologen (MV2+) initially exchanged in a zeolite Y modified carbon paste electrode (ZMCPE) is reduced after being exchanged for the supporting electrolyte cation. The use of an electrolyte cation that cannot enter zeolite channels to a great extent does not give rise to appreciable currents while a non‐size‐excluded cation allows liberating MV2+ from zeolite particles and their subsequent reduction at the electrode–solution interface. Following those observations, the MV2+‐based ZMCPE has been used for the constant potential (−0.85 V) amperometric detection of nonreducible:, non‐size‐excluded cations in aqueous medium. The performance of this electrode was investigated in both batch injection analysis (BIA) and flow injection analysis (FIA). The great advantage of BIA coupled to the amperometric detection is the ability to use electrolyte‐free sample solutions. For FIA experiments, dissolved oxygen was eliminated by using an electrochemical scrubber containing porous carbon electrodes. With the MV2+‐doped ZMCPE, alkali and alkali‐metal cations can be detected at the submillimolar level for both batch and flow injection analysis.
Determination of metal–organic complexation in natural waters by SWASV with pseudopolarograms
Authors: Lewis B. L. , Luther G. W. , Lane H. , Church T. M. 
Published: May 2005

AbstractA novel electrochemical method is described for the examination of metal–organic complexation in natural waters. The technique is based upon the comparison of square wave anodic stripping voltammetry (SWASV) ‘pseudopolarograms’ (current vs. deposition potential plots) for natural samples with those obtained for metal complexation with selected ‘model’ binding ligands at constant ionic strength. For electrochemically active zinc species in seawater, the pseudopolarogram approach allowed the estimation of thermodynamic stability constants (KML) within a stability constant window of approximately 104–106 M−1 up to ≥ 1015 M−1. For a natural rainwater sample, the pseudopolarogram indicated only one zinc class, probably a mixture of ‘free’ and/or inorganically complexed species. In an application to a coastal seawater sample, three species were identified: (1) weakly complexed, log KZnL = 4.14 ± 0.92 M−1; (2) moderately complexed, log KZnL = 7.77 ± 0.62 M−1; (3) strongly complexed, log KZnL = 11.45 ± 0.95 M−1. Results are compared to those obtained using complexometric titration with SWASV at a thin mercury film–glassy carbon rotating disk (TMF–GCRD) electrode. The latter detected a single strong complexing ligand (or ligand class), with [L′] = 15.25 ± 0.04 nM and log K′ZnL ≥ 10.9 M−1.
Carbon paste electrodes with electrolytic binder: Influence of the preparation method
Authors: Ramírez M. T. , Palomar M. E. , González I. , Rojas‐Hernández A. 
Published: May 2005

AbstractA method for the construction of carbon paste electrodes (CPE) is described. Here ferrocene is used as the insoluble electroactive species, graphite powder as conductor and sulfuric acid as binder. The CPE thus prepared prevents ferrocenium ions from diffusing towards the bulk solutions. Voltammetric, chronopotentiometric and chronoamperometric experiments performed with these CPEs show that the different preparation methods yield different electrochemical parameters for the ferrocene–ferrocenium system.
Oxidative behavior of aminohalogenbenzophenones – indirect determination of benzodiazepinooxazoles
Authors: Fernández M. C. , Alonso R. M. , Jiménez R. M. , Rodríguez F. J. 
Published: May 2005

AbstractAn electroanalytical study of three aminohalogenbenzophenones: 2‐amino‐5‐chlorobenzophenone (MCB), 2‐amino‐2′,5‐dichlorobenzo‐phenone (DCB), and 2‐amino‐5‐bromo‐2′‐fluorobenzophenone (BrFB); metabolites of the psychotropic drugs benzodiazepinooxazoles and benzodiazepines, has been carried out at a glassy carbon electrode using different voltammetric techniques. The compounds studied are electrooxidizable in a hydroalcoholic medium (MeOH:H2O, 10 : 90), 0.5 M KC1, and a pH range of 1–13. The oxidation processes are irreversible and predominantly diffusion controlled. On the basis of the oxidation process, voltammetric methods have been developed that allow the determination of aminohalogenbenzophenones from 0.2 to 15ppm for MCB and BrFB, and 0.2 to 14ppm for DCB; with a reproducibility in terms of relative standard deviation (RSD) lower than 5.2% for 10 determinations of 10 ppm solutions of MCB, DCB, and BrFB. Detection limits of 200ppb (μg/L) for MCB and DCB, and 100ppb for BrFB were obtained. The voltammetric method developed for DCB has been applied to the indirect determination of Cloxazolam in tablets.
Polarographic behavior of 2‐carboxybenzaldehyde thiosemicarbazone and the indirect trace determination of palladium(II) ions in catalysts
Authors: Cabanillas Augustina Guiberteau , Espinosa‐Mansilla Anunciación , Salinas Francisco , López‐de‐Alba Pedro L. 
Published: May 2005

AbstractThe electrochemical characteristics of 2‐carboxybenzaldehyde thiosemicarbazone (2CBTSC) have been studied by differential pulse polarography (DPP) and cyclic voltammetry (CV) at a mercury electrode. This new thiosemicarbazone is reduced in a two‐electron irreversible step at the nitrogen double bond of the side chain at pH 1.82. An anodic peak situated very close to the oxidation response of mercury has been observed by DPP in neutral and alkaline media. Determination of 2CBTSC based on the reduction peak is possible in the range of 5 × 10−8 M to 8 × 10−6 M, with a relative standard deviation of 2.3% in the middle of the range and a detection limit of 7.6 × 10−9 M (1.7 ng/mL). The decrease in the reduction peak of the thiosemicarbazone after the addition of Pd(II) has been used for the development of precise and sensitive amperometric determination of palladium in catalysts with an average relative error of 1.1% and a determination limit of 6ppb of Pd(II) (5.6 × 10−7 M).