bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new electrochemical method for the investigation of the aggregation of dyes in solution
Authors: Gooding Justin J. , Compton Richard G. , Brennan Colin M. , Atherton John H. 
Published: May 2005

AbstractA new electrochemical technique is presented for the investigation of aggregation phenomena in solution over a wide range of solution conditions. Developed nominally for dyes, the method is, in principle, applicable to any electroactive compound. The method employs microelectrodes to measure the change in the diffusion limited current, with concentration, of the aggregating species of interest. At the onset of aggregation, the relationship between this limiting current and concentration deviates from linearity. This deviation, due to the slower rate of diffusion of aggregates, is related to the degree of association of the molecule, assuming a molecular weight distribution of aggregates and using an established relationship between the effective diffusion coefficient and molecular weight. The technique is contrasted with an existing spectroscopic method.
Fabrication of a polyglycine chemically modified electrode and its electrocatalytic oxidation to ascorbic acid
Authors: Yu Ai‐Min , Zhang Hai‐Li , Chen Hong‐Yuan 
Published: May 2005

AbstractCyclic voltammetry was used to investigate the electrochemical polymerization of glycine at the glassy carbon electrode. The applied voltage range, pH of electrolyte, concentration of monomer, and cyclic number were found to affect the polymerization process. The resulting film displayed a catalytic activity towards the oxidation of ascorbic acid (AA), reducing the overpotential by 350 mV. A catalytic reaction rate constant of 5.86 × 104 M−1 s−1 was determined using a rotating electrode. Hydrodynamic voltammetric experiments were performed to characterize the electrode as an amperometric sensor for the determination of AA. At 0.4 V (in pH 7.0 PBS) the detection limit is 4.0 × 10−8 M (SIN = 3). The linear dynamic range was wide, from 6.0 × 10−8 to 2.5 × 10−4 M.
Carbon paste electrodes plated with a gold film for the voltammetric determination of mercury(II)
Authors: Švancara Ivan , Matoušek Milan , Sikora Eugen , Schachl Klemens , Kalcher Kurt , Vytřas Karel 
Published: May 2005

AbstractCarbon pastes of different compositions were tested as supports for gold film electrodes. A paste containing highly‐viscous silicone oil as a binder was found the most suitable. Experimental conditions were optimized in order to develop a differential pulse anodic stripping voltammetric method for the determination of mercury in water samples. In a supporting electrolyte containing HNO3 (0.1 mol/L), (KCl 0.02 mol/L) and tetrachloroaurate(III) for in situ plating with a gold film, the response of Hg was found to be linear in a concentration range from 1 × 10−9 up to 2.5 × 10−7 mol/L (0.2–50 μg/L; accumulation potential +0.2V (vs. Ag/AgCl); accumulation time 30 s–5 min) with a detection limit of about 2.5 × 10−10 mol/L (50 ng/L) after accumulating for 30 min. Reliability of the method depended mainly on the concentration of AuIII in the electrolyte which had to be chosen adequately, with respect to the concentration level of HgII in the sample. Interferences from some ions with the determination of mercury were also studied. The method was tested on both model and real samples and the results agreed well with those obtained by reference determinations.
Effect of varying quaternary ammonium salt concentration on the potentiometric properties of some trifluoroacetophenone derivative‐based solvent‐polymeric membranes
Authors: Hong Young Ki , Yoon Woo Jin , Oh Hyun Jun , Jun Young Moo , Pyun Hyung‐Jung , Cha Geun Sig , Nam Hakhyun 
Published: May 2005

AbstractPotentiometric properties of carbonate‐selective membranes based on some trifluroacetophenone derivatives [e.g., trifluoroacetyl‐p‐decylbenzene (TFADB), 1,7‐bis(4′‐trifluoro‐acetophenyl)‐4‐decyl‐1,7‐dioxo‐2,6‐dioxy‐heptane (compound I) and 1,2‐bis(4‐trifluoroacetylbenzoyloxymethyl)‐benzene (compound II)] with varying concentration of tridedecylmethyl ammonium chloride (TDMACl) have been examined. It was observed that both TFADB‐ and compound‐II‐based membranes with about 50 mol % TDMACl (relative to the carrier) exhibit the maximum selectivity for carbonate. On the other hand, the compound‐I‐based membranes with about 50 mol % TDMACl showed the greatest discrimination of lipophilic anions (ClO4−, salicylate, SCN3−) including NO, but those with about 80 mol % against Cl− and CH3COO−. These results conform well to the theoretical model developed by Simon et al. if we assume trifluroacetophenone derivatives form 2:1 and/or 3:1 complexes with the anions in the plasticized PVC‐based membranes. Molecular mechanics calculations indicated that bis‐trifluroacetophenones may not form 1:1 complex with the carbonate ion because of a large steric hindrance between the two bulky adjacent chains.
On‐line flow sensor for measuring acetylcholine combined with microdialysis sampling probe
Authors: Horiuchi Tsutomu , Torimitsu Keiichi , Yamamoto Katsunobu , Niwa Osamu 
Published: May 2005

AbstractWe have developed an on‐line electrochemical sensor for the continuous measurement of acetylcholine (ACh). The sensor comprises a small volume prereactor containing immobilized choline oxidase (ChOx) and catalase (or horseradish peroxidase, HRP), a small volume enzymatic reactor containing immobilized acetylcholine esterase (AChE) and ChOx and a glassy carbon electrode modified with Os‐polyvinylpyrridine ‐HRP. The sensor can measure ACh selectively even when the choline (Ch) concentration is more than 1000 times that of ACh, when th ChOx and catalase are immobilized in the prereactor. The sensor shows a wide linear relationship from 5 nM to 1 μM and a detection limit of 5 nM (S/N = 2), which is comparable to the ACh detection limit achieved by liquid chromatography/electrochemistry. It also shows high selectivity against other neurotransmitters and interferents. The properties of the sensor combined with a microdialysis (MD) probe were also studied by measuring a solution containing a much higher concentration of Ch than ACh.
Redox and adsorption processes of hydrolyzed uranyl species on a mercury electrode from sodium chloride solutios
Authors: Djogić Renata , Krznarić Damir , Branica Marko 
Published: May 2005

AbstractReduction and adsorption processes of hydrolyzed uranyl species on the mercury drop electrode, from 0.55 mol L−1 NaCl, were studied by electrochemical cathodic stripping techniques: cyclic voltammetry, alternating current voltammetry, chronoamperometry and double potential step chronocoulometry. The only uranyl species adsorbed on the Hg electrode (between pH 5 and 7) was found to be uncharged uranyl dihydroxide, as well as its reduction product. At bulk concentrations between 3 and 5 μmol L−1 that reactant forms an adsorbed compact film as a result of surface polymerization, nucleation or other condensation processes. The adsorption isotherm at pH 6.2 and −0.2 V was measured. It was fitted with a Frumkin type isotherm. At the plateau. a reduction current corresponding to 6.7 × 10−9 mol cm−2 of uranyl ions was measured. This represents on the average 7 adsorbed layers of UO2(OH), presuming an orthorhombic crystal cell structure. Multilayer adsorption is certain even if a polymeric form of uranyl dihydroxide was considered.
Adsorptive stripping voltammetric measurements of chromium accumulation in mice organs using mercury film microelectrodes
Authors: Pereira Maria C. , Pereira Maria L. , Sousa João P. 
Published: May 2005

AbstractChromium is the metallic species of most concern with the use of stainless steel implants. To study the distribution of chromium in mice organs with time, several animals were subcutaneously injected with 2.70 × 10−3 mol/L of chromium solution during a certain period of time. Square wave voltammetry using adsorptive collection of Cr3+ ‐DTPA complex on a mercury film microelectrode (MFM) was used for quantitation. Optimized conditions included DTPA concentration of 2.0 × 10−2 mol/L, sodium acetate 4.0 × 10−2 mol/L, sodium nitrate 0.40 mol/L, potassium permanganate 1.0 × 10−3 mol/L, pH ca. 6.1, deposition potential of −1.15 V, deposition time 20 s, frequency 100 Hz, step 2.5 mV and an amplitude of 20 mV. The detection limit of the method was 1.54 × 10−8 mol/L after deposition of 20s. Other species presented in the biological material such as calcium and iron do not interfere with the chromium determinations. The accuracy of the proposed method was checked by comparing the results with those obtained by atomic absorption spectrometry (AAS) yielding good agreement. The results showed an increase of chromium levels with time in liver, kidney and spleen, indicating that this metal is partially accumulated in the studied organs.
Differential pulse voltammetric determination of fenobucarb at the glassy carbon electrode, after its alkaline hydrolysis to a phenolic product
Authors: Cabanillas Agustina Guiberteau , Díaz Teresa Galeano , Salinas Francisco , Ortiz Juan Manuel , Kauffmann Jean Michel 
Published: May 2005

AbstractA differential pulse voltammetric method for the determination of fenobucarb is proposed. This N‐methylcarbamate pesticide is hydrolyzed in alkaline medium (0.02 M NaOH during ten min), and the resulting product 2‐sec‐butylphenol is oxidized at the glassy carbon electrode giving rise to a peak at a potential near 750 mV (pH 3.5). The linear relationship between Ip and fenobucarb concentration was established up to 1.00 × 10−4 M concentration, the detection limit was 3.68 × 10−6 M. The RSD is 3.74% for a 1.0 × 10−5 M concentration (n = 11, p = 0.05). The method has been satisfactorily applied to the analysis of water samples spiked with the pesticide.
Electrical contact of redox enzyme layers associated with electrodes: Routes to amperometric biosensors
Authors: Willner Itamar , Katz Eugenii , Willner Bilha 
Published: May 2005

AbstractTailoring of electrically contacted enzyme electrodes provides the grounds for bioelectronic and biosensor systems. Redox‐enzymes organized onto electrodes as monolayer assemblies, and chemically functionalized by redox‐relay groups, yield electrically contacted enzyme electrodes exhibiting bioelectrocatalytic features. The sensitivity of the enzyme electrode can be enhanced, or tuned, by the organization of multilayer enzyme electrodes and the application of rough metal supports. Enzyme electrodes of extremely efficient electrical communication with the electrode are generated by the reconstitution of apo‐flavoenzymes onto relay‐FAD monolayers associated with electrodes. The reconstitution process results in an aligned enzyme on the surface, and its effective electrical contact with the electrode yields selective enzyme electrodes of unprecedented high current responses. Integrated electrodes consisting of relay‐NAD(P)+‐cofactor and enzyme units are generated by the reconstitution of NAD(P)+‐dependent enzymes onto a relay‐NAD(P)+ monolayer assembly followed by lateral crosslinking of the enzyme network.
Stabilization of an osmium bis‐bipyridyl polymer‐modified carbon paste amperometric glucose biosensor using polyethyleneimine
Authors: Jezkova Jitka , Iwuoha Emmanuel I. , Smyth Malcolm R. , Vytras Karel 
Published: May 2005

AbstractThe modification of carbon paste electrodes by incorporation of the enzyme glucose oxidase (GOx) and a conducting redox osmium bis‐bipyridyl poly(4‐vinylpyridine) polymer (Os‐polymer) is described. The resulting enzyme electrodes were operated as amperometric glucose sensors in the presence or absence of a stabilizer, polyethyleneimine (PEI), mixed into the paste. Cyclic voltammetric studies showed that Os‐polymer containing Os2+/3+ redox couple mediated the electron transfer from reduced GOx to the carbon paste electrode material. Steady‐state amperometric responses of the sensors to 2–120 mM glucose at an operating potential of 350 mV (vs. Ag/AgCl) were determined in 0.1 M phosphate buffer (pH 7.0) medium. The study showed that PEI enhances both, the sensitivity and stability of the carbon paste enzyme electrode and that a diffusion‐limited step precedes electrocatalytic reactions of the biosensor. Cyclic voltammetric data and the Arrhenius analysis of the apparent turnover rate constant, k′cat showed that PEI decreases the diffusion limitations of CPE, thereby increasing the frequency of collision of reacting species in this biosensor format.
A new macrocyclic polystyrene based membrane sensor for zinc
Authors: Singh Ashok K. , Bhattacharjee G. , Singh Manendra , Chandra Sudeshna 
Published: May 2005

AbstractA quadridentate dihydrogen perchlorate macrocyclic membrane is found to exhibit quite promising selectivity for Zn2+. It can be used to estimate zinc in the range 2.5 × 10−6 to 1.0 × 10−1 mol dm−3 (0.16 to 6.50 × 103 mg dm−3) with a near‐Nernstian slope of ≈︁ 28 mV per decade of concentration. The working pH range of the sensor is 3.0 to 7.0. The polystyrene based membrane electrode is found to possess adequate stability and specific selectivity with a response time of 10 s. Most of the ions that interfere with Zn2+ electrode do not cause any significant disturbance with this assembly and the sensor can be used for more than three months in aqueous as well as in partially nonaqueous media. The utility of the membrane sensor has also been observed in solutions contaminated with detergent matter. The membrane sensor has also been used successfully to analyse some baby food products and soft drinks for the determination of Zn2+ ions.
Voltammetric response of myoglobin at a modified silver electrode
Authors: Zhu Junjie , Gong Yue , Zhang Jinjie , Shen Pingping , Chen Hongyuan 
Published: May 2005

AbstractA silver electrode coated with captopril, 1‐[(2S)‐3‐mercapto‐2‐methyl‐1‐oxopropyl]‐L‐proline, was prepared by covalent bonding method. The modified electrode was long‐lived and stable. Experimental results revealed that myoglobin (Myb) could exhibit good voltammetric response at the modified electrode. Square wave voltammetric measurements of Myb with the modified electrode gave a linear relationship between the anodic peak current and the protein concentration in the range of 4 × 10−6 −5 × 10−5 mol/L. The relative standard deviation is 5 % for 6 successive determinations in 2 × 10−5 mol/L Myb.
A carbon dioxide biosensor based on hemoglobin incorporated in metal supported bilayer lipid membranes (BLMs): Investigations for enhancement of response characteristics by using platelet‐activating factor
Authors: Siontorou Christina G. , Nikolelis Dimitrios P. , Krull Ulrich J. 
Published: May 2005

AbstractThe present article reports the development of a novel electrochemical carbon dioxide minisenso based on hemoglobin which is incorporated into self‐assembled bilayer lipid membranes (s‐BLMs) on a metal support. The presence of carbon dioxide in solution was found to modulate the ion conductivity of BLMs containing hemoglobin, when using a lipid composition containing egg phosphatidylcholine (egg PC) and dipalmitoylphosphatidic acid (DPPA). The use of stabilized metal‐supported BLMs has allowed the electrochemical investigation of the reversibility of the response to carbon dioxide and of hemoglobin binding to lipid membranes. The effects of hemoglobin concentration, composition of BLMs in DPPA and pH on the sensitivity of the response were examined. The sensor provides the advantages of fast response times (on the order of ca. 10 s) to alterations of carbon dioxide concentration, low detection limits (ca. 0.4 × 10−6 M) and capability of analysing small sample volumes. Semisynthetic platelet‐activating factor (PAF; 1‐O‐alkyl‐2‐acetyl‐sn‐glyceryl‐3‐phosphorylcholine, AGEPC) was found to improve the response characteristics of the carbon dioxide sensor (i.e., decrease of the detection limit to nM range and increase of the dynamic range of carbon dioxide determination). The biosensor was routinely mechanically stable and functional for over 48 h. During this time it showed reproducible sensitivity and response to a given concentration of carbon dioxide in solution.
Detection of carbamate pesticides in vegetable samples using cholinesterase‐based biosensors
Authors: Skládal Petr , Nunes Gilvanda Silva , Yamanaka Hideko , Ribeiro Maria Lucia 
Published: May 2005

AbstractBiosensors for determination of carbamates in vegetables based on five different cholinesterase as biorecognition elements and a screen‐printed electrode system as an amperometric transducer were developed. Measurements were simply performed by dropping solutions (either sample or substrate) directly on the biosensor. The response of biosensors to selected carbamates (aldicarb, carbaryl, carbofuran, methomyl and propoxur) was characterized. The performance was evaluated on extracts of potatoes and carrots, the results from the AChE biosensor and a standard HPLC procedure were compared. Finally, the biosensor was used for the direct analysis of vegetable juices without any pretreatment steps. In this case, 10 μg/L levels of added carbofuran and propoxur were reliably identified. The whole procedure takes less than 20 min including 10 min incubation with samples. The concentrations of carbamates determined with biosensor agreed well for carbofuran. Lower response was observed for propoxur.
Ion‐exchange voltammetry of trace mercury(II) at glassy carbon electrodes coated with a cationic polypyrrole derivative. Application to pore‐waters analysis
Authors: Ugo Paolo , Sperni Laura , Moretto Ligia M. 
Published: May 2005

AbstractGlassy carbon electrodes modified with coatings of poly‐[1‐methyl‐3‐(pyrrol‐1‐ylmethyl)pyridinium], poly‐MPP, were prepared by electrochemical oxidation of the suitable monomer in acetonitrile solutions. The anion exchange properties of the coated electrode were exploited in aqueous solutions for preconcentrating and detecting the anionic complex HgCl42−, which is the prevailing inorganic HgII species in seawater and other chloride media. The partition coefficients for the ion‐exchange equilibrium involved were calculated from voltammetric data and compared with those obtained at electrodes coated with Tosflex, a perfluorinated anion exchanger, and poly(vinylpyridine). The selectivity of the poly‐MPP coated electrodes towards the rejection of copper interference was also studied. The optimization of experimental conditions allowed the development of a differential pulse voltammetric method for the determination of submicromolar mercury concentrations with a detection limit of 0.1 nM. The method was applied to the analysis of mercury in the pore‐waters of tidal sediments of the Lagoon of Venice (Italy), determining HgII concentration values in the 70–80 nM range.
Modeling of a CdII–N‐(2‐hydroxyethyl)ethylenediamine system and optimization of stability constants by the use of complex formation curves. A polarographic study at a fixed L:M ratio and varied pH
Authors: Cukrowski Ignacy 
Published: May 2005

AbstractThe ligand N‐(2‐hydroxyethyl)ethylenediamine (HEEN) was studied with CdII by differential pulse polarography (DPP) at fixed total ligand (LT) to total metal (MT) concentration ratios and varied pH at 25°C and an ionic strength μ = 0.5 mol dm−3. The polarographic experimental complex formation curve (ECFC) and calculated complex formation curve (CCFC) were used for modeling of the metal‐ligand system and the refinement of stability constants. The ECFC, in which experimental parameters of polarographic peaks are included (a shift in a peak potential and a variation in a peak height) appears to be a characteristic function for a particular metal‐ligand system studied at a particular LT : MT ratio. 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 for which the CCFC fits best the ECFC. Four cadmium complexes CdL2+, CdL, CdL, and CdL2 (OH)+ and their stability constants as log β found from DPP 5.08 ± 0.03, 9.44 ± 0.04, 11.25 ± 0.05, 12.06 ± 0.03, respectively, are reported. The complex CdL was found for the first time. Results obtained in this work are compared with literature data.
Electrochemical detection of mercury adsorbed from flowing gas samples on porous carbon electrodes
Authors: Huang Min , Huang Meiju J. , Faguy Peter W. , Pan Wei‐Ping 
Published: May 2005

AbstractThe adsorption of mercury from flowing gas streams onto reticulated vitreous carbon (RVC) is combined with postadsorption stripping voltammetric determination. This novel analytical method achieves gas stream detection limits of 1.1 μg/m3 for unmodified RVC electrodes at 52°C and 1.8 μg/m3 for modified RVC electrodes at 25°C. Due to the unique features of this detection technique, it is possible and feasible that it could be applied for mercury analysis in coal fired power plant plumes and waste incinerator stacks.
Peroxidase‐based amperometric sensor of hydrogen peroxide generated in oxidase reaction: Application to creatinine and creatine assay
Authors: Kinoshita Hideaki , Torimura Masaki , Kano Kenji , Ikeda Tokuji 
Published: May 2005

AbstractPeroxidase (POD) was entrapped on a ferrocene (Fc)‐embedded carbon paste (CP) electrode with a dialysis membrane to construct a POD‐Fc‐CP electrode for the reductive amperometric determination of hydrogen peroxide (H2O2). The electrode allowed the H2O2 detection down to 10 nM (under stirring), with a linear relation up to 15 μM, and without change of the response over one month. On the other hand, a plastic‐formed carbon (PFC) electrode can donate electrons to POD without any specific mediator. The POD‐entrapped PFC electrode produced a relative current density of 24% compared with the POD‐Fc‐CP electrode. The reductive detection of H2O2 with the POD‐Fc‐CP electrode was applied to the determination of creatinine and creatine in serum and urine using sarcosine oxidase, creatine amidinohydrolase, and creatinine amidohydrolase as the reagents. The significance of the membrane‐covered POD‐Fc‐CP electrode in the coupling of the oxidase reaction is also discussed.
Split square‐wave voltammograms of surface redox reactions
Authors: Mirčeski Valentin , Lovrić Milivoj 
Published: May 2005

AbstractA fast and simple method for the estimation of kinetic parameters of surface redox reactions, based on the splitting of their square‐wave voltammograms, is proposed. A mathematical procedure for simulation of these processes is developed. The method can be applied for the fast and chemically reversible redox reactions which are characterized by the kinetic parameter K ≥ 0.8 (K = ks/f). The standard rate constant, transfer coefficient and standard redox potential of the redox reaction of alizarine‐red S adsorbed on the mercury electrode in pH 9 medium are ks = 60 ± 10s−1, α = 0.45 ± 0.03 and E° = −0.810 ± 0.005V (vs. Ag/AgCl‐KCl).
A novel iron‐porphyrin‐derived oxygen sensor working near 0 V (vs. Ag/AgCl) in neutral solution
Authors: Wu Xuanzheng , Li Yijun , Gründig Bernd , Yu Nai‐Teng , Renneberg Reinhard 
Published: May 2005

AbstractA metalloporphyrin film modified platinum (Pt) electrode was prepared by electrochemical polymerizing of iron(III)‐tetra(3‐methoxy‐4‐hydroxy‐phenyl) porphyrin on a platinum electrode. Cyclic voltammetry of the electrode in PBS pH 7.0 shows the dioxygen reduction peak close to 0 V (vs. Ag/AgCl). Rotating disk electrode experiments indicate a four‐electron transfer mechanism of dioxygen reduction. The chemically modified electrode is recommended as a potential oxygen sensor working at a relatively low potential.