bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion‐sensitive field‐effect transistors and ion‐selective electrodes as sensors in dynamic systems
Authors: Izquierdo Andrés , de Castro María D. Luque 
Published: May 2005

AbstractThe state‐of‐the‐art of both ion‐sensitive field‐effect transistors (ISFETs) and ion‐selective electrodes (ISEs) when working in continuous flow systems is reviewed. The features and development of each type of sensor are established, and the advantages of the use of one or the other are discussed.
Kinetic study of electrocatalytic reduction of hydrogen peroxide at iron(III) porphyrin modified glassy carbon electrode in alkaline medium using the rotation‐scan method
Authors: Dong Shaojun , Liu Baifeng , Liu Junli , Tabard Alain , Guilard Roger 
Published: May 2005

AbstractReduction of hydrogen peroxide at a glassy carbon (GC) electrode modified with σ‐bonded pyrrole iron(III) octaethylporphyrin complex, (OEP)Fe(Pyr), was studied by cyclic voltammetry and a rotating disk electrode. In 0.1 N NaOH solution, it is shown that such an (OEP)Fe(Pyr)/GC electrode has a significant catalytic activity towards hydrogen peroxide reduction (ED = −0.80 V, k = 0.066 cm s−1); however, the electrode stability is low. The deactivation is observed when the reaction charge (Q) is passing through the (OEP)Fe(Pyr)/GC disk electrode. A linear rotation scan method is applied to study the kinetic process by determining the disk electrochemical response (iD) to rotation rate (ω) at a definite disk potential (ED). Considering that the number of adsorbed electroreduced catalyst molecules (Red) varies according to the disk potential, a factor θ (= ΓRed/(ΓRed + ΓOx)) is introduced to describe the electrode surface area fraction for electroreduced species. The obtained Koutecky–Levich equation is applicable whatever the potential is.
Voltammetric and photoelectron spectral elucidation of the electrocatalytic oxidation of hydrogen peroxide at screen‐printed carbon electrodes chemically modified with cobalt phthalocyanine
Authors: Gilmartin Markas A. T. , Ewen Richard J. , Hart John P. , Honeybourne Colin L. 
Published: May 2005

AbstractThe interplaying mechanisms involved in the electrocatalytic oxidation of hydrogen peroxide (H2O2) have been studied using cyclic and differential‐pulse voltammetry and X‐ray photoelectron spectroscopy (XPS). Cobalt phthalocyanine (CoPC) modified screen‐printed carbon electrodes (SPCEs) were used as base transducers in the voltammetric studies, and for XPS experiments a mixture of the printing ink containing CoPC was coated onto a steel stub. These investigations have shown that CoPC is initially in the Co2+ oxidation state, and that in plain supporting electrolytes it is subsequently electrochemically oxidized to Co3+. A postulated sequence of events for the mediated oxidation of H2O2 at CoPC‐SPCEs has been derived from the XPS and voltammetric data generated.
Carbon paste electrode incorporated with cobalt(II) octaethoxyphthalocyanine for the amperometric detection of hydrogen peroxide
Authors: Mizutani Fumio , Yabuki Soichi , Iijima Seiichiro 
Published: May 2005

AbstractA hydrogen peroxide sensing electrode was prepared by incorporating cobalt(II) octaethoxyphthalocyanine [CoPc(OEt)8] into a carbon paste (CP) matrix. The CoPc(OEt)8‐modified electrode could oxidize hydrogen peroxide at lower potentials than a CP electrode with unsubstituted cobalt phthalocyanine (CoPc). In addition, the CoPc(OEt)8‐based system showed a high stability; the electrode response to 10mM hydrogen peroxide did not decrease for over 6 h, whereas the hydrogen peroxide response from the CoPc‐modified electrode reduced to half the initial value within 2 h. The CoPc(OEt)8, which is a paraffin oil soluble derivative of CoPc, incorporated into the bulk of the CP diffused towards the electrode surface so as to renew the electrode surface, and this resulted in the high stability of the CoPc(OEt)8‐modified electrode. The electrode was used as the transducer for an L‐lactate‐sensing enzyme sensor; the sensor could be used for more than 4 weeks and 400 assays.
Nitrite‐selective electrode based on an electropolymerized cobalt phthalocyanine
Authors: Allen John R. , Florido Antonio , Young Shelley D. , Daunert Sylvia , Bachas Leonidas G. 
Published: May 2005

AbstractCobalt(II) 4,4′,4″,4″′‐tetraaminophthalocyanine was electropolymerized on glassy carbon by cyclic voltammetry. The formed polymeric films were shown to interact selectively with anions and were used in the design of ion‐selective electrodes. Different polymerization conditions, as well as different conditioning solutions and buffer systems, were investigated in order to optimize the response of the electrodes. The electrodes were found to be most selective for nitrite. The slopes of the calibration plots were sub‐Nernstian and the detection limit for nitrite was 1.7 × 10−4 M.
Highly sensitive biosensing of phenolic compounds using bioaccumulation/chronoamperometry at a tyrosinase electrode
Authors: Wung Joseph , Chen Qiung 
Published: May 2005

AbstractBiocatalytic accumulation is used to greatly enhance the sensitivity of tyrosinase enzyme electrodes for phenolic compounds. By allowing the enzymatic reaction to proceed for different time periods (under open‐circuit conditions) it is possible to accumulate the quinone product near the transducer surface. The subsequent chronoamperometric response is substantially higher than analogous bioassays without accumulation. For example, with 3 min accumulation, a 28‐fold signal amplification is observed. Assays of microliter (40 μL) samples are reported, yielding a detection limit of 2 × 10−8M (88 pg) catechoi following a 3 min accumulation. The influence of various experimental variables is explored. Applicability to bioassay of relevant environmental samples is illustrated.
Pulse polarography study of the complexes of lead with azacrown [2,2,2]cryptand in the presence of an excess of competing sodium ion
Authors: Cukrowski Ignacy , Marsicano Fabrizio , Hancock Robert D. , Cukrowska Ewa 
Published: May 2005

AbstractDifferential pulse polarography (DPP) has been used to determine the formation constants of PbII at ionic strength 0.5 M and 25 °C with [2, 2, 2]cryptand in the presence of 0.5 M sodium nitrate. The equilibrium between Pb2+ and the ligand is established slowly on the polarographic time scale, so that two well‐separated peaks are observed, that for the metal ion and for a nonlabile ML complex for which the stability constant was found to be log K1 = 12.9. The equilibrium between the ML complex and hydroxide ion appeared to be fast and a substantial shift in the peak potential of the ML complex was observed. Two labile lead complexes are reported, namely ML(OH) and ML(OH)2 for which stability constants (log β) were found to be 20.51 and 23.75, respectively. The Lingane equation has been modified to allow calculation of formation constants for labile complexes of lead with two ligands, [2, 2, 2]cryptand and OH−. A single, second, overall protonation constant of [2, 2, 2]cryptand at an ionic strength of 0.5 M and 25°C in the presence of 0.5 M Na+ is reported and its value was found to be log β2 = 18.
Electrochemical oxidation of DNA at a gold microelectrode
Authors: Pang Dai‐Wen , Qi Yi‐Peng , Wang Zong‐Li , Cheng Jie‐Ke , Wang Jia‐Wang 
Published: May 2005

AbstractThe electrochemical oxidation of DNA at a gold microelectrode has been investigated using cyclic voltammetry with a homemade microliter cell. Denatured DNA is adsorbed and oxidized more easily at the gold electrode than native DNA. The electrochemical oxidation of DNA also depends on its strand length. The DNA oxidation product adsorbs strongly on the gold electrode, so poisoning and inactivating its surface; the adsorbed product also inhibits electrooxidation of the gold surface.
Electrochemical behavior of NbV–EDTA and NbV–citrate systems in aqueous solutions
Authors: Gomes Maria Das Graças , Franco Douglas W. 
Published: May 2005

AbstractThe electrochemical reduction of NbV using oxalatoniobic acid and ammonium oxooxalatoniobate salts was studied in aqueous solutions of citric acid and sodium ethylenediaminetetraacetate (EDTA), in a wide range of supporting electrolyte concentrations and pH. In EDTA two reduction processes were observed: NbV to NbIV, E = −1.000 V vs. Ag/AgCl at pH 4.50 and NbIV to NbIIIE = −1.400 V vs. Ag/AgCl (pH 4.50). In citric acid there was only one reduction process: (NbV to NbIV), E = −1.260 V vs. Ag/AgCl at pH 4.50. In both electrolytes a linear relationship was found between the diffusion current and the niobium concentration in the 1.0 × 10−5 to 5.0 × 10−3 M range. Using cyclic voltammetry, it waa observed that the charge transfer process in the NbV to NbIV process is reversible in EDTA and reversible–quasireversible in citric acid.
Reminiscences of Professor Wilhelm Simon and his research work at the ETH Zürich
Authors: Morf Werner E. , Pretsch Ernö 
Published: May 2005

AbstractThe Symposium on Electrochemical Sensors was dedicated to the memory of the late Professor Wilhelm Simon. We all remember him as a remarkable and renowned scientist, and as an enthusiastic and inspiring lecturer. In particular, he was a pioneer in research on ion‐selective electrodes. With this article, the authors would like to pay due reverence to him and to his outstanding contributions to analytical chemistry.
Studies on the phase boundaries and the significance of ionic sites of liquid membrane ion‐selective electrodes
Authors: Bühlmann Philippe , Yajima Setsuko , Tohda Koji , Umezawa Kayoko , Nishizawa Seiichi , Umezawa Yoshio 
Published: May 2005

AbstractAttenuated total reflectance infrared spectroscopy (ATR‐IR) has been used to study the cation permselectivity of liquid‐membrane ion‐selective electrodes (ISEs). All spectroscopic evidence was found to agree with the interpretation of permselectivity as being due to complete exclusion of counter‐ions from the boundary phase. Compared to ATR‐IR, optical second harmonic generation (SHG) has an even more pronounced surface sensitivity. It has been demonstrated to be a promising new technique for the study of ISE response mechanisms, as it allows one to observe the actual phase boundary. On the other hand, further potentiometric evidence for the influence of ionic sites on the emf response was found, both by a study of membranes free of ionic sites as well as by the investigation of leaching processes at poly(viny1 chloride) membranes. Finally, the use of a photoresponsive crown ether ionophore allowed the determination of emf response characteristics in relation to the ionophore concentration without any changes in the membrane composition.
Computer modeling of the membrane–solution interface of liquid membrane ion‐selective electrodes
Authors: Vincze Arpad , Horvai George , Leermakers Frans A. M. 
Published: May 2005

AbstractThe potentiometric behavior of liquid membrane ion‐selective electrodes with neutral carrier has been qualitatively reproduced by a computer model. Phenomena like Nernstian response, cation and anion interference, detection limit and the effect of lipophilic salt additives could be successfully modeled.
Some recent studies on the use of electrochemical sensors in nonaqueous solution chemistry
Authors: Izutsu Kosuke , Nakamura Toshio , Arai Tomoko , Ohmaki Masayuki 
Published: May 2005

AbstractFour recent studies in the authors' laboratory on the use of electrochemical sensors in nonaqueous solutions are reported. (1) Si3N4‐ and Ta2O5‐type ISFETs proved to be useful in nonaqueous solutions as sensors for pH and for proton solvation, because of their more rapid response than a conventional glass electrode. They were used to study the acid–base equilibria in γ‐butyrolactone and to determine the proton transfer activity coefficients between different solvents. (2) A univalent cation‐sensitive glass electrode was used to study the solvation of lithium ions in mixed solvents applicable to lithium batteries. (3) A membrane of polyacrylamide coupled to a cobalt phthalocyanine complex and coated onto a platinum electrode functioned as a sensor for fluoride and cyanide ions in aprotic solvents. It was used to determine the solubility products of alkali and alkaline earth metal fluorides and cyanides in acetonitrile and propylene carbonate. (4) A new method is proposed for the estimation of the liquid junction potential between different solvents, and a comparative study has been made between the new method and some conventional methods.
A solid composite pH sensor based on quinhydrone
Authors: Düssel Heike , Komorsky‐Lovrić Šebojka , Scholz Fritz 
Published: May 2005

AbstractA solid composite pH sensor can be made from quinhydrone, solid paraffin and surface‐modified graphite powder. It exhibits an almost theoretical slope of the potential–pH dependence (−57.7 mV at 25°C), a formal potential E0′ = 0.6922V (vs. NHE), low standard deviations for repeated measurements (0.04 pH units), fast potential response (15s) and a working range up to pH 9.5. The sensor can be used in moderately concentrated mineral acids and, unlike the conventional quinhydrone electrode, it is also applicable for measurements in milk. The sensor shows the same salt effect and sensitivity towards strong oxidants and reductants as the conventional quinhydrone electrode. The surface modified graphite was prepared by boiling graphite powder with concentrated nitric acid. By voltammetry it was shown that the surface of the modified graphite contains surface‐confined redox centers similar to those in quinhydrone, which can catalyze the electron transfer of the quinhydrone on the surface of the sensor.
Characterization of modified electrodes by electrochemical quartz crystal microbalance, radiotracer technique and impedance spectroscopy
Authors: Inzelt György 
Published: May 2005

AbstractThe significance and reliability of the data determined by different in‐situ methods (electrochemical quartz crystal microbalance, radiotracer and impedance spectroscopy) on the film formation and redox transformations of polymers are discussed. Results on both redox and conducting polymer films are selected in order to illustrate the practical and theoretical problems of the field.
Potentiometric oxygen sensing with copper films: Response mechanism and analytical implications
Authors: Meruva Ravi K. , Meyerhoff Mark E. 
Published: May 2005

AbstractThe electrochemical response mechanism of a previously reported potentiometric oxygen (O2) sensing system based on thin films of copper sputtered on single crystal Si(100) is examined. The potentiometric O2 response of such films is shown to depend on sample stirring rate as well as the pH, ionic strength and nature of the buffer salts within the test solution. XPS studies of the copper films exposed to solution for several days confirm the presence of compper corrosion products on the surface. These findings, in conjunction with cyclic voltammetric measurements, suggest that the potentiometric O2 response originates from slow corrosion of copper and simultaneous reduction of O2 at the surface of the thin films. A steady‐state situation exists when the rates of these two reactions are equal, resulting in a corrosion potential (also referred as rest potential Er for the system) that varies in a near Nernstian (1 e−) manner with the partial pressure of O2 in solution. A mathematical formulation for this type of response, based on the Butler–Volmer equation, is presented. The analytical implications of these findings with respect to devising useful potentiometric O2 sensors based on copper films are discussed.
The effect of a nonadsorbing electroactive species on the transition time in derivative adsorptive chronopotentiometric stripting analysis
Authors: Honeychurch Michael J. , Ridd Michael J. 
Published: May 2005

AbstractA theory to describe the enhancement of the transition time and change in peak shape for the chronopotentiometric reduction of an adsorbed species caused by the reduction of an electroactive diffusing species is presented. The equations were derived for planar, cylindrical and spherical electrodes and verified for the chronopotentiometric reduction of adsorbed cystine, as mercurous cysteine thiolate, on a hanging mercury drop electrode in the presence of dissolved oxygen.
Solid‐state hydrogen sensor based on a solid‐polymer electrolyte
Authors: Samec Zdeněk , Opekar František , Crijns Guido J. E. F. 
Published: May 2005

AbstractAn electrochemical hydrogen sensor has been constructed, based on two platinum electrodes that differ in their true‐to‐geometrical surface area ratios and that are in contact with Nafion. The electrodes attain different mixed potential values in air containing hydrogen and thus the sensor does not require a reference atmosphere (pure air). The potential difference between the electrodes can be used for potentiometric or amperometric detection of hydrogen. The detection sensitivity strongly depends on the relative humidity (RH) of the test air. Within a hydrogen concentration range from 40 to 4000ppm (v/v) and with RH varying between 33 and 95%, the sensitivity of potentiometric detection decreases with increasing RH from 149 to 113 mV per concentration decade, while that for amperometric detection increases from 0.67 to 1.25 nA/ppm. On a step change in the hydrogen concentration, a value of 95% of stationary response is attained within ca. 140 s for potentiometric detection and ca. 50s for amperometric measurement.
Study on electrocatalytic oxidation of NADH by ferrocene derivatives and determination of catalytic rate constant at microdisk electrode
Authors: Tian Min , Dong Shaojun 
Published: May 2005

AbstractThe electrocatalytic oxidation of NADH by ferrocene derivatives and the influence of complexation with β‐cyclodextrin (β‐CD) were investigated at a microdisk electrode in a buffer solution. The cyclic voltammetric behavior of the ferrocene derivatives on the microdisk electrode was used to determine the electron‐transfer rate constant from NADH to the ferricinium species. The heterogeneous rate constants and the diffusion coefficient of ferrocene derivatives were determined with the microdisk electrode. The effect of temperature and pH on the electrocatalytic oxidation of NADH were assessed.
Ion‐exchange voltammetry at polymer‐coated electrodes: Principles and analytical prospects
Authors: Ugo Paolo , Moretto Ligia M. 
Published: May 2005

AbstractThis review describes principles and analytical applications of ion‐exchange voltammetry (IEV) at polymer modified electrodes. Results of mechanistic studies which are relevant to the development and optimization of IEV methods are discussed. Useful examples of IEV determinations of traces of inorganic and organic electroactive ions of interest for environmental, biomedical or pharmaceutical analysis are given along with future prospects for this technique.
On‐line amperometric assay of glucose, L‐glutamate, and acetylcholine using microdialysis probes and immobilized enzyme reactors
Authors: Yao Toshio , Suzuki Seita , Nishino Hirohito , Nakahara Taketoshi 
Published: May 2005

AbstractA highly selective on‐line, real‐time monitoring system is proposed for amperometric assay of glucose, L‐glutamate, and acetylcholine. The system includes a microdialysis probe, immobilized enzyme reactor, and poly(1,2‐diaminobenzene)‐coated platinum electrode. The analyte in the dialysate from the microdialysis probe is enzymatically converted to produce hydrogen peroxide. The hydrogen peroxide is detected selectively at a poly(l,2‐diaminobenzene)‐coated platinum electrode, without any interference from oxidizable species and proteins. The present method can be successfully applied to in vitro assay of glucose and in vivo monitoring of glucose in rat brains. However, the sensitivity is not sufficient for in vivo monitoring of trace amounts of L‐glutamate and acetylcholine in rat brains.
A portable flow injection analyzer for use with ion‐selective electrodes
Authors: Dimitrakopoulos Telis , Alexander Peter W. , Hibbert D. Brynn , Cherkson Len , Morgan John 
Published: May 2005

AbstractA battery powered portable monitor based on flow injection potentiometry has been developed weighing 1.8 kg, constructed in a carry‐case and applicable for remote site monitoring. Portability has been achieved using a light weight rechargeable Ni‐Cd battery‐pack (7.2 V). The flow injection manifold incorporates a low powered peristaltic pump, a wall‐jet type flow cell containing a commercial iodide ion‐selective electrode and a Ag/AgCl reference electrode connected to an analog‐to‐digital converter, also powered by the battery pack, and a RS232‐serial output to a notebook computer for real‐time data display and storage. The system performance has been evaluated using the iodide ion‐selective electrode, including the effects of various carrier solutions on sample peak heights, peak widths and the calibration slopes and working ranges. Fast response with peak widths as low as approximately 10 s. was observed with near Nernstian response of −53.8 mV change per activity decade and a log‐linear range between 5 × 10−6 and 1 × 10−2M in a 0.1 M sodium acetate carrier stream.
Electrochemical reduction of o‐nitrophenol as a tool for the rough characterization of organic matter in seawater samples
Authors: Gas̆parović Blaz̆enka , Ćosović Božena 
Published: May 2005

AbstractPhase sensitive alternating current (AC) voltammetry with o‐nitrophenol (ONP) as a probe is used as a simple nondestructive method for a rough characterization of organic substances in natural seawater samples. This is based on the measurement of the effects of adsorbed organic substances on the peak height and the potential of the ONP reduction peak. In this work further improvements are presented of the method which is achieved by introducing the measurement of the prepeak of ONP reduction obtained upon scan reversal. The height of the prepeak is extremely sensitive to the type of organic matter adsorbed on the mercury electrode at the pH of natural seawater. The ONP prepeak increases in the presence of adsorbed layers of negatively charged organic substances, such as humic and fulvic acids and proteins. In the presence of adsorbed polysaccharides of dextran type there is no increase of the ONP prepeak height. With increasing concentrations of the polysaccharides a small decrease of the prepeak is observed. The application of the method is demonstrated on different seawater samples from the north Adriatic sea.
Voltammetric behavior of pyrimethamine in veterinary formulations using square‐wave and adsorptive square‐wave techniques
Authors: Berzas J. J. , Rodríguez Juana , Lemus J. M. , Castañeda G. 
Published: May 2005

AbstractThe voltammetric behavior of pyrimethamine (PMT) was studied by square‐wave (SW) and square‐wave stripping (SWS) techniques, leading to two methods for its determination [in presence of sulfaquinoxaline (SQX)] in aqueous samples and veterinary formulations. Due to overlapping response of SQX and PMT the first derivative was used for the simultaneous determination of these two components. The relative standard deviations obtained for concentration levels of PMT as low as 3 × 10−6 M (SW) and 5 × 10−7 M (SWS) were 2.2% and 2.7% (n = 10), respectively.
The electrochemical behavior of methylene blue at a microcylinder carbon fiber electrode
Authors: Ju Huangxian , Zhou Jun , Cai Chenxin , Chen Hongyuan 
Published: May 2005

AbstractThe electrochemical behavior of methylene blue (MB) at a carbon fiber microcylinder electrode, was studied by cyclic voltammetry. The charge transfer coefficient α of the electrode reaction with two‐electron transfer is 0.5, and the number of H+ participating in the electrode process is 3 at pH 2.2–5.4, 2 at pH 5.4–6.0 and 1 at pH 6.0–10.7, respectively. The standard electron transfer rate constant ko′, and standard formal potential Eo′ of MB at various pH were determined by using the carbon fiber microcylinder electrode. The electrode reaction mechanism of methylene blue at various pH is proposed. The adsorbability of MB at the electrode is discussed and explored by cyclic voltammetry and chronocoulometric technique.