bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of photopolymerized decyl methacrylate as a membrane matrix for ion‐selective electrodes
Authors: Ambrose Theresa M. , Meyerhoff Mark E. 
Published: May 2005

AbstractPotentiometric ion‐selective sensors based on photopolymerized thin films of decyl methacrylate (DMA) crosslinked with hexanedioldimethacrylate (HDDMA) are described. The electrochemical response characteristics including slopes, selectivities, resistances and response times of several DMA‐based ion‐selective electrodes are reported and compared to those obtained using PVC‐based sensors. Sensors incorporating the nonspecific anion exchanger tridodecylmethylammonium chloride and the plasticizer dioctyl sebacate exhibit a Nernstian response to chloride with the expected Hofmeister selectivity pattern. Additional response data for potassium and carbonate selective sensors prepared with the electrically neutral ionophores valinomycin and p‐decyltrifluoroacetophenone, respectively, are also presented. The eflects of endogenous anionic sites arising from dissociated methacrylic acid impurities within the membrane matrix are discussed. The degree of site dissociation and its resulting contributions to the EMF response‐governing equilibria are considered in detail. It is shown that such sites must be electrically compensated (via addition of adequate lipophilic cationic sites) when preparing neutral‐ carrier based anion sensors but otherwise have no apparent effect on the sensing membranes' selectivity and performance.
Potentiometric pH sensor with anthraquinonesulfonate adsorbed on glassy carbon electrodes
Authors: Shiu Kwok‐Keung , Song Fayi , Dai Hong‐Ping 
Published: May 2005

AbstractElectrochemically activated glassy carbon electrodes adsorbed with anthraquinonesulfonate species showed potentiometric responses toward pH changes for pH range between 1 and 11, with a near Nernstian slope of about 56.4 mV/pH and a lifetime of more than one month. The effects of electrode pretreatment and preparation conditions, as well as the effects of interfering ions on the electrode response were studied.
Sol‐gel‐derived metal‐dispersed carbon composite amperometric biosensors
Authors: Wang Joseph , Pamidi Prasad V. A. , Park Deog Su 
Published: May 2005

AbstractThe advantages which accrue from the coupling of sol‐gel enzyme electrode preparation processes with the dispersion of electrocatalytic metal centers are described. In particular, ruthenium‐dispersed sol‐gel carbon thick‐film bioelectrodes couple the low‐temperature curing process with the elimination of contributions from easily oxidizable interfering species. The remarkable selectivity towards the glucose substrate is combined with a greatly enhanced sensitivity. Factors influencing the performance of these sol‐gel‐derived metal‐doped enzyme strips are discussed.
Redox reactions in the presence of an ion‐exchange/hydrogel composite film
Authors: Somasundrum Mithran , Bannister Joe V. 
Published: May 2005

AbstractThe formation of a composite ion‐exchange/hydrogel membrane using a mixture of Nafion and poly(vinyl alcohol), is described. The structure of the composite is investigated by following the cyclic voltammetry of anionic redox couples present in bulk solution, and by following the diffusional characteristics of cationic redox couples entrapped within the films. Hydrophobic redox species exhibit greater rates of diffusion within the composite films than within films of homogeneous Nafion. The films show greater resistance to protein adsorption than cellulose acetate or poly(carbonate). Electrical communication between co‐immobilized enzyme (glucose oxidase) and hydrophobic mediator is demonstrated.
Voltammetric study of chiral active compound 4,4′‐diisopropyl‐2,2′‐thiazoline and its interaction with copper(II)
Authors: Mlakar Marina , Čuljak Ivan , Daković Senka , Branica Marko 
Published: May 2005

AbstractThe electrochemical investigation of the chiral active compound, (4S)‐4‐diisopropyl‐2‐2′‐bithiazoline (DPT), commonly used in asymmetric syntheses as well as in diastereoselective reactions, and its interaction with copper(II) ion by cathodic stripping voltammetry at a HMDE electrode, was performed. DPT reduction occurs in two steps, at potentials about −0.2 and −0.45V (vs. Ag/AgCl), through the formation of an electrodeposited layer of DPT‐Hg at the electrode surface. DPT complex with copper(II) is reduced at about −0.36 V, through the formation of DPT‐Cu deposit at the electrode surface. The reduction process of DPT‐Hg and DPT‐Cu complex, as well as DPT, depend upon pH, on the electrolyte solution, as well as on the concentration and ratio of the ligand and metal ion. The mechanisms of those electrode processes were investigated. Due to their strong adsorption, low concentration levels of DPT, through DPT‐Hg complex reduction, and copper, through DPT‐Cu complex reduction, about 10−9 M, can be determined, with the accumulation time of 10 minutes at 0.0 V (vs. Ag/AgCl), at pH 2.8 in 0.55 M NaCl.
Detection of hydrogen peroxide and other molecules of biologicl importance at an electrocataltic surface on a carbon fiber microelectrode
Authors: Nowall Wilbur B. , Kuhr Werner G. 
Published: May 2005

AbstractThe electrocatalytic oxidation of hydrogen peroxide in solution at a modified carbon fiber electrode has been investigated. A simple electrochemical procedure has been developed to dramatically improve the voltammetry for the peroxide, NADH, and several other species under steady state and fast scan voltammetry. The surface is generated by the electrochemical oxidation of NASH followed by exposure to peroxide. This procedure yields a surface which is sensitive to peroxide and stable in air for more than 90 days. This oxidation occurs at a potential such that it is easily discriminated from the analytes tested in this study.
Diffusion coefficients of gallium(III) in potassium nitrate and potassium chloride supporting electrolytes
Authors: Kariuki Stephen , Dewald Howard D. 
Published: May 2005

AbstractThe diffusion coefficient values of GaIII in potassium nitrate and potassium chloride supporting electrolytes have been obtained polarographically. The half‐wave potential, E1/2, and E3/4‐E1/4 values have also been determined. The E3/4 ‐ E1/4 values confirm the irreversibility of GaIII reduction in KNO3 and KCl electrolytes.
Use of neural networks in solving interferences caused by formation of intermetallic compounds in anodic stripping voltammetry
Authors: Lastres Ernesto , de Armas Graciela , Catasüs Miguel , Alpízar Jesüs , García Luciano , Cerdà Víctor 
Published: May 2005

AbstractNeural networks (NNs) were used to overcome interferences by formation of intermetallic compounds in anodic stripping voltammetry (ASV). The software developed for this purpose allows one to construct NNs of virtually any type of architecture and train it automatically using the back‐propagation method. The ability of NNs for addressing interferences arising from interactions with the hanging mercury drop electrode is demonstrated for the Cu–Zn binary system.
Calix[4]Arenes in the partial cone conformation as ionophores in silver ion‐selective electrodes
Authors: O'Connor Katherine M. , Henderson William , O'Neill Eva , Arrigan Damien W. M. , Harris Stephen J. , McKervey M. Anthony , Svehla Gyula 
Published: May 2005

AbstractTwo calix[4]arene derivatives, in the partial cone conformation, with sulfur‐containing functionalities, were tested as neutral carrier ionophores in potentiometric silver‐selective electrodes of conventional membrane and membrane‐coated glassy carbon electrode types. Comparison with a calix[4]arene in the cone conformation was made. The membranes were prepared using either 2‐nitrophenyl octyl ether or bis(ethylhexyl)sebacate as plasticizers and potassium tetrakis(p‐chlorophenyl)borate as the lipophilic salt in a poly(vinyl chloride) matrix. Both calix[4]arenes yielded electrodes of good sensitivity (approx. 47 mV dec−1) in the range 10−4–10−1 M and excellent selectivity [log KAg,MH+ < −1.5] of transition, alkali and heavy metal cations, including sodium, mercury(II) and lead(II) cations. Temperature effects and reproducibility of response were determined and the interfering effects of mercury(II) and lead (II) ions on the membranes were noted. The partial cone conformation allows improved selectivity over certain cations relative to calix[4]arenes in the cone conformation.
The determination of copper at thin film electrodes by constant current stripping potentiometry
Authors: Bradshaw Mark P. , Scollary Geoffrey R. 
Published: May 2005

AbstractA comparison of the determination of copper by constant current stripping potentiometry (CCSP) at mercury and gold films has been carried out. The preferred solution conditions for the mercury film study were determined to be 0.1M ammonium acetate at pH 4.5 and 0.1M HCl for the gold film study. The influence of chloride on the stripping signal was investigated and it was found that for the mercury film conditions, well‐formed stripping signals could be obtained up to a chloride concentration of 0.5 M which permitted the ready determination of copper in seawater. With the gold film, high chloride concentrations affected both the film stability and the glassy carbon surface and repeatable results were difficult to obtain. The optimized CCSP methods were applied to various aqueous samples including tap water, seawater, TCLP (acetic acid) extracts as well as TCLP extracts using groundwater and ocean water. Based on the results obtained for these various matrices, it was concluded that there are several advantages favoring the mercury film. The interference from organic components in the sample matrix on the general applicability of CCSP for the determination of copper at either a mercury or gold film is discussed.
Electroreduction of some pyridine carboxamides on carbon electrodes in aqueous solutions
Authors: Angulo Matiide , Montoya Mercedes Ruiz , Galvin Rafael Marin , Mellado José Miguel Rodriguez 
Published: May 2005

AbstractThe electroreductions of the NAD+ model compounds nicotinamide (I), N1‐methyl nicotinamide (II), N′‐methyl nicotinamide (III) and isonicotinamide (IV) on carbon electrodes have been studied in aqueous media in the pH range 0–12 by linear‐sweep cyclic voltammetry (Scheme 1, I‐IV). Logarithmic analyses of the reduction peaks were performed by computing the convolution of the current with time as a function of the potential. On the basis of the experimental results it was concluded that the irreversibility of the electron transfers increased when a glassy carbon electrode was used, and this irreversibility being more marked when a plastic formed carbon electrode was employed. The reduction processes occurred with more difficulty on carbon electrodes than on mercury electrodes. Both the reduction and the reoxidation (when occurred) processes changed with respect to those observed on mercury electrodes, being irreversible electron transfers the rate‐determining steps in most cases. Thus, for compounds I, II and III at pH < 2 the reductions occurred by the uptake of two electrons and two H+ ions, and the rate determining step was found to be the first one‐electron transfer, for I and III, and the irreversible second electron transfer, preceded by the uptake of an H+ ion, for II. At pH>3 the processes consisted of electrodimerization reactions, preceded by the protonation of the heterocyclic nitrogen in cases I and III. The second electron transfer of the electroreduction of IV always appeared irreversible, in contrast with that found for mercury electrodes.
Electroanalysis in flowing systems – the propagation of depletion effects downstream of a channel micro‐band electrode
Authors: Bidwell Matthew J. , Alden John A. , Compton Richard G. 
Published: May 2005

AbstractAnalytical and numerical methods are used to establish concentration distributions around channel microband electrodes both in isolation and as part of multi‐electrode arrays. The importance of axial diffusion in addition to convection and diffusion normal to the electrode surface is stressed. In particular, downstream depletion effects are shown to occur over many electrode lengths, so that the diffusion fields of electrodes within arrays overlap and interfere. A simple analytical expression is derived to describe this depletion and permits the design of practical arrays in which electrodes operate essentially independently of each other.
Electrochemical sensing of gases based on liquid collection interfaces
Authors: Huang Huiliang , Dasgupta Purnendu K. 
Published: May 2005

AbstractAlthough many electrochemical gas sensors have been reported, electrochemical gas sensors based on liquid collection constitute a smaller subset. Minimally, a liquid interface based electrochemical gas sensor is composed of two electrodes and an ion conducting electrolyte. There is a large number of possible arrangements of these parts, and many choices exist for their composition and preparation methods. This results in a diverse and rich technology now available for gas sensing. The measurement of some analyte gases of interest, notably ozone, nitrogen oxides, hydrogen peroxide, formaldehyde, ammonia, sulfur dioxide and hydrogen sulfide are specifically discussed. Finally, the recent reviews that are likely to be the most relevant to the further development of electrochemical detection approaches for gases with a liquid collection interface are cited and discussed.
Dimethylglyoxime doped sol‐gel carbon composite voltammetric sensor for trace nickel
Authors: Wang Joseph , Pamidi Prasad V. A. , Nascimento Valberes B. , Angnes Lucio 
Published: May 2005

AbstractA new class of modified sol‐gel carbon composite electrodes, based on the encapsulation of complexing ligands, is described. Such modified electrodes couple the versatility and tunability of sol‐gel processes with the advantages of the preconcentration/voltammetric strategy. The incorporation of the ligand dimethylglyoxime (DMG) within the carbon‐silicate ceramic network is used to illustrate the new concept in connection with the voltammetric sensing of trace nickel. The sol‐gel carbon composite serves as a favorable host matrix for DMG, which retains its nickel binding characteristics. Factors influencing the sensor response, including the sol‐gel hydrolysis time, DMG loading or preconcentration time are explored. The electrode displays good linearity up to 800 μg/L nickel, a detection limit of 15 μg/L (following a 5 min accumulation), and a relative standard deviation of 7.7%. Applicability to assays of river water is illustrated. Doping of other ligands into sol‐gel carbon composites should result in similar voltammetric sensors for other important metals.
Experimental and calculated complex formation curves as an optimization tool in speciation studies of polarographically labile metal‐ligand systems
Authors: Cukrowski Ignacy 
Published: May 2005

AbstractThe PbII‐N,N′‐di‐2‐picolylethylenediamine (DPA‐2) system was studied by differential pulse polarography (DPP) and glass electrode potentiometry (GEP) at fixed total‐ligand to total‐metal concentration ratio and varied pH. The polarographic experimental complex formation curve (ECFC) and calculated complex formation curve (CCFC) are used for modeling of a metal‐ligand system and the refinement of stability constants. The ECFC is used instead of a shift in the peak potential plotted vs. pH and it appears to be a characteristic function for a particular metalligand system. The CCFC is a theoretical curve calculated for the assumed metal‐ligand model from mass‐balance equations. The final model of metal species formed is the one which is accepted by these two experimental techniques and for which stability constants of metal complexes obtained from DPP and GEP differ the least. Four lead complexes Pb(HL), PbL, PbL2(OH) and PbL(OH)2 and their stability constants as log β found from DPP 12.67 ± 0.08, 9.68 ± 0.07, 16.12 ± 0.08 and 14.88 ± 0.06, respectively, are reported. Results obtained from GEP and DPP differ only within experimental errors typical for these techniques.
Anodic stripping voltammetry at hydrodynamic mercury thin film electrodes. Numerical simulation of stripping peaks for reversible processes at uniformly accessible electrodes
Authors: Ball Jon C. , Compton Richard G. 
Published: May 2005

AbstractThe time dependent backwards implicit method is used to simulate the shape and position of the stripping peaks in DC (linear scan) anodic stripping voltammetry at mercury thin film hydrodynamic electrodes for electrochemically reversible systems. The effect of variable diffusion layer thickness, assumed uniform and experimentally controllable in the case of rotating disk systems, in influencing both the peak potential and peak shape, is quantified and the implications for anodic stripping voltammetry under convective conditions noted.
Determination of adenine and guanine by capillary zone electrophoresis with end‐column amperometric detection at a carbon fiber microdisk array electrode
Authors: Jin Wenrui , Wei Huiying , Zhao Xin 
Published: May 2005

AbstractCapillary zone electrophoresis was employed to the analysis of adenine and guanine by using end‐column amperometric detector with a carbon fiber microdisk array electrode. Optimum conditions of separation and detection are 0.01 mol/L H3PO4–0.01 mol/L H3BO3–0.01 mol/L HAc‐NaOH (pH 9.2) for the buffer solution, 20 kV for the separation voltage, 3.0 kV and 5 s for injection voltage and time, respectively, and 1.00 V (vs.SCE) for the detection potential. The limit of detection is 8.2 fmol for adenine and 2.9 fmol for guanine (S/N = 2). The method was applied to determination of adenine and guanine in hydrolytic product of yeast‐RNA and calf thymus‐DNA.
Determination of trace vanadium in various waters by differential pulse adsorptive stripping voltammetry
Authors: Rao K. Sreenivasa , Palrecha M. M. , Dhaneshwar R. G. 
Published: May 2005

AbstractA sensitive voltammetric method is developed for the determination of trace amounts of vanadium in various water samples. The method is based on the preconcentration of the VV‐2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol (5‐Br‐PADAP) complex at a potential of −0.5 V (vs. Ag/AgCl). The adsorbed complex is then reduced, producing a response with a peak potential of −0.8 V. The catalytic action of bromate ions on the reduction of the VV‐5‐Br‐PADAP complex has also been investigated. The high catalytic currents obtained in presence of bromate ions are taken advantage of enhancing the sensitivity of the method. From the preliminary studies the optimal conditions for the determination of vanadium by differential pulse adsorptive stripping voltammetry have been established. The interference of various elements in this method has also been studied. The method of standard addition is employed in evaluating the concentration of vanadium in water samples. The determination limit is 20 ng/L and the RSD is 12% for vanadium concentrations of 500 ng/L.
Potentiometric detection of metal ions separated by liquid chromatography using a tungsten oxide electrode
Authors: Chen Zuliang , Alexander Peter W. 
Published: May 2005

AbstractThe use of a tungsten oxide sensor for the potentiometric detection of metal ions separated by liquid chromatography is described. Separation of metal ions such as Fe3+, Fe2+, Cu2+ and Pb2+ was performed by ion chromatography using a mobile phase containing 25 mM sodium tartrate/2 mM ethylenediamine at pH 3.8. Calibration plots were linear in the range 0.5 to 3.5 mM. Potentiometric detection was also applied to ion‐interaction chromatography. The results showed that separation of metal ions was improved and the detection limits for the test metals in the range of 0.5–5 nmol were obtained in the presence of sodium citrate/1‐octanesulfonic acid at pH 3.0. The potentiometric detection described in this article is shown to have advantages in terms of low cost, simplicity and sensitivity.
Electrocatalytic activity of a C60‐γ‐cyclodextrin (1:1) and nafion chemically modified electrode to hemoglobin
Authors: Li Mei‐Xian , Li Nan‐Qiang , Gu Zhen‐Nan , Zhou Xi‐Huang , Sun Yi‐Liang , Wu Yong‐Qing 
Published: May 2005

AbstractThe electrochemical behavior of films of C60‐γ‐cyclodextrin (1:1) and Nafion has been studied in an aqueous solution. A reversible surface‐confined one‐electron‐transfer electroreduction wave was detected by cyclic voltammetry. The CME displayed electrocatalytic activity to hemoglobin in a 0.10 M KCl solution.
Electropolymerization of amphiphilic monomers for designing amperometric biosensors
Authors: Cosnier Serge 
Published: May 2005

AbstractThe principle and potentialities of an original electrochemical procedure of biosensor construction based on amphiphilic pyrrole derivatives are reviewed. The two‐step procedure consists of the adsorption of an aqueous amphiphilic pyrrole monomers–biomolecule mixture on an electrode surface followed by the electrochemical polymerization of the adsorbed amphiphilic monomers. This method is compared with the more conventionally used electrochemical procedures of biosensor construction. Examples of multienzyme and additive entrapments, organic phase enzyme electrode, microelectrode functionalization and the electrical wiring of immobilized enzymes are presented.
Potentiometric response behavior of parallel arrays of cation‐ and anion‐selective membrane electrodes as reference devices
Authors: Morf Werner E. , de Rooij Nicolaas F. 
Published: May 2005

AbstractThe potential response of reference devices consisting of parallel arrays of cation‐ and anion‐selective membrane electrodes is studied on a theoretical basis. A general treatment of the overall electric potential difference is offered that accounts for contributions by diffusion potentials, boundary potentials, ohmic potential drops, and streaming potentials. Explicit solutions are given for special cases. The treatment makes it possible to recognize the capabilities and the limitations of membrane‐based reference devices, and to compare their performance with the behavior of conventional reference electrodes using liquid‐junction contacts. The applicability of membrane‐based reference systems is found to be restricted to relatively specific samples.
Diphenhydramine‐selective plastic membrane sensor and its pharmaceutical applications
Authors: Erdem Arzum , Ozsoz Mehmet , Kirilmaz Levent , Kilinc Emrah , Dalbasti Tayfun 
Published: May 2005

AbstractDifferent types of PVC‐matrix ion‐selective electrodes (ISEs) that respond to the cationic form of diphenhydramine (Dph) are described. Three ion‐pairing agents, namely tetraphenylborate (TPB), phosphotungstate (PT), reineckate (RN) are investigated. The best PVC polymeric membrane contains Dph‐TPB as active material. The electrode, based on the ion‐pair complex with TPB anion shows near‐Nernstian response in the concentration range 10−2 to 3.5 × 10−5 M (Dph.HCl). Changing pH within the range 2.0–7.5 did not affect the electrode performance. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coeffcient of the electrode (0.00156 V/°C) The electrode showed a good selectivity for Dph with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were applied to determine Dph amounts in pharmaceutical preparations. The Dph selective membrane electrode was also applied to the determination of the dissolution profile of Dph tablets. The dissolution results were compared with spectrophotometrically determined ones.