bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigations in bioanalytical chemistry part VIII: Derivative adsorption chronopotentiometry of the CuII complex with adenine, adenosine and adenosine monophosphate
Authors: Zhao Xin , Jin Wenrui , Tang Jian 
Published: May 2005

AbstractThe derivative adsorption chronopotentiometric characteristic of the CuII complex with adenine, adenosine and adenosine monophosphate (AMP) is discussed. The optimum experimental conditions and the linear ranges were studied. The detection limits of adenine, adenosine and AMP were 2.2 × 10−9, 4.5 × 10−8 and 4.6 × 10−8 mol/L, respectively.
Determination of traces of RNA in submicrogram amounts of single‐ or double‐stranded DNAs by means of nucleic acid‐modified electrodes
Authors: Fojta Miroslav , Doftlková Renata , Palečhk Emil 
Published: May 2005

AbstractRecently we have utilized the advantages of nucleic acid‐modified mercury electrodes to develop a method capable of determining RNA traces in samples of double‐stranded DNA [1]. It was, however, impossible to determine less than 10 % of RNA in a single‐stranded DNA sample. Here we show that the DNA voltammetric signals can be selectively suppressed by precipitation with [Co(NH3)6]3+ while the signal of any RNA digested with RNase A is not influenced. Following from our studies we proposed a voltammetric method for determination of less than 1% of RNA in microgram samples of single‐ and double‐stranded DNA.
Carbon film based ring‐disk and split‐disk dual electrodes as detectors for microbore liquid chromatography
Authors: Niwa Osumu , Morita Musao , Solomon Bruce P. , Kissinger Peter T. 
Published: May 2005

AbstractThe electrochemical properties of carbon film based ring‐disk and split‐disk electrodes in small active volume (0.24–2μL) radial flow cells were studied in order to employ them in conjunction with microbore liquid chromatography (LC) for determining catecholamines. The high conversion of dopamine (DA) at the disk of a ring‐disk electrode makes the DA limiting current lower than the theoretical value at a low flow rate. The collection efficiency (CE) increases with decreasing flow rate and cell thickness, which is different from previously reported results. A high CE of 0.96 was achieved because of the narrow gap of 5 μm.On the other hand, a higher limiting current was observed with the split‐disk than with a commercially available dual‐disk electrode because of its efficient geometry for analyte collection. The cross talk of the DA after reacting at one of the electrode is only 2%. The ring‐disk and split‐disk electrodes were suitable as series and parallel electrochemical detectors for small bore LC. A detection limit of 103 fg was obtained for DA at the disk of the ring‐disk because of the high signal in the thin‐layer radial flow cell and the low noise level of the carbon film. In contrast, very slight interference was observed from neighboring electrodes when determining catecholamines at the split‐disk.
Enzymatic electrode for the determination of L‐lactate
Authors: Boujtita Mohamed , Chapleau Muriel , Murr Nabil El 
Published: May 2005

AbstractAn amperometric L‐lactate biosensor was constructed by confining lactate oxidase and a redox mediator in a carbon paste electrode. Conditions for optimal electrode response were determined by varying the modified carbon paste composition. Using hydroxymethyl ferrocene as a redox mediator resulted in an improvement of sensitivity and linearity range of the electrode. The sensor showed a repeatability and accuracy compatible with industrial use.
Polarographic study of the coordinated system ZnII‐alanine‐alaninate ion
Authors: González Manuel De La Cuesta , Sánchez Mariana Cuesta , Morales Juan C. Ruiz , Placeres Jesús C. Rodríguez 
Published: May 2005

AbstractPolarography has been applied to the study of the mixed‐ligand system ZnII‐alanine‐alaninate, in aqueous medium, at I = 1.0 M NaClO4 and 25 ± 0.05°C. The study of the quasireversible waves characteristic of ZnII has been carried out by means of a new method of analysis, which is faster and more accurate than traditional methods. The stabilization of the coordinated species [ZnA]2+ (β10 = 1.8), [ZnA2]2+ (β20 = 0.52), [Zn(A−)]+ (β01 = 9.1 × 104), [Zn(A−)2] (β02 = 9.4 × 108) and [ZnA(A−)]+ (β11 = 6.2 × 104) has been established.
Voltammetric monitoring of photochemical reactions: Photo‐induced electron transfer to p‐chloronitrobenzene
Authors: Kumbhat Sunita , Webster Richard , Marken Frank , Eklund John C. , Compton Richard G. 
Published: May 2005

AbstractChannel electrode voltammetry using an irradiated gold electrode is used to study the photolysis of p‐chloronitrobenzene in aqueous ethanolic solution in the presence of the hydroxide anion. The formation of the stable radical anion, [p‐CIC6H4NO2]•−, via light‐induced electron transfer is demonstrated and kinetic parameters are reported.
Electrochemically prepared and optimized membrane compositions for silver(I)‐responsive chalcogenide‐based ion‐selective electrodes
Authors: Neshkova Milka T. , Pancheva Elka M. 
Published: May 2005

AbstractThrough electrochemical modeling, an attempt has been made to correlate the composition, structure and stoichiometry of a number of thin electroplated silver chalcogenide (selenides and tellurides) all‐solid‐state membranes with their performance as Ag‐responsive ion‐selective electrodes. The conclusions drawn from the electrochemical membrane composition modeling could be of practical value to the pressed‐pellet technology as well. The results suggest that no binary silver chalcogenide, irrespective of its stoichiometry, could perform reliably in an all‐solid‐state configuration. On the contrary, hyperstoichiometric membranes featuring both intrinsic and extrinsic defects, e.g., Ag2+δSe1−xTex have proved to exhibit high sensitivity, potential reproducibility and selectivity (even to mercury) under both steady‐state and flow‐injection modes. The competitiveness of the newly developed electroplated membranes to conventional Ag2S pressed ones has been assessed.
The preparation and sensor application of poly(p‐aminophenol)
Authors: Ekinci Ergun , Karagözler A. Alev , Karagözler A. Ersin 
Published: May 2005

AbstractAn amperometric biosensor for glucose based on a novel polymeric matrix is described. The sensor was prepared by electrochemical polymerization of p‐aminophenol in the presence of glucose oxidase on Pt substrates in a KCl solution at a potential of 0.6 V (vs. Ag/AgCl). The chronoamperometric response of poly(p‐aminopheno1)‐glucose oxidase biosensor to hydrogen peroxide formed as the result of enzymatic reaction was measured at a potential of 0.7 V (vs. Ag/AgCl) in PBS solution. It was shown that a biosensor prepared by this one‐ step procedure has a linear range up to 6mM glucose, a response time less than 5 s and a lifetime around 15 days. The sensitivity of the electrode was superior to that of much publicized polypyrrole based glucose oxidase electrode. Also, the substrate selectivity of PAP/GOx electrode was tested for coexisting substances such as lactose, sucrose, urea, paracetamol, uric and ascorbic acid and no discernible anodic response was observed above the background current.
Automatic chemical current determination in coulometric stripping potentiometry facilitating calibration‐free trace metal determinations
Authors: Jagner Daniel , Wang Yudong , Ma Feng 
Published: May 2005

AbstractThe theory of an improved coulometric stripping potentiometry method, involving automatic determination of the chemical current for each sample, and thus suitable for calibration‐free determination of trace elements in microliter samples is described. The method has been applied to the determination of ZnII, CdII, PbII, TlI, CuII and BiIII by reductive in situ amalgamation and of AsV, SnIV and CuII by reductive in situ dissolution on a gold film followed by three consecutive constant current stripping potentiometry measurements permitting the determination of the chemical current. Quantitative reduction (≥99%) of the analyte ions was obtained after four minutes of vibrationally enhanced reductive electrolysis of the 12μL samples placed on top of an inverted glassy carbon disk electrode combined with Ag and Ag/ AgCl counter and reference electrodes. The concentration detection limits ranged from 11 nM for elements oxidized to the monovalent state to 3 nM for elements oxidized to the trivalent state. The mass detection limits ranged from 4.5 pg for ZnII to 28pg for TlI.
Conversion from electronic conducting phase to redox conducting phase of polypyrrole
Authors: Yang Chunhe , Dong Shaojun 
Published: May 2005

AbstractSquare‐wave voltommetry is used to study the oxidation of polypyrrole doped with dodecylsulfate. The net current curve in this experiment shows why the oxidation current does not display the capacitive‐like shape common in cyclic voltammetry. In cyclic voltammetry, the redox behavior of polypyrrole is attributed to the size of dodecylsulfate, irreversible incorporation and the complete consumption of dodecylsulfate. After the polypyrrole film was scanned in aqueous NaCl solution, square wave voltammetric measurements show different results, indicating the change of the polymer nature with regard to the charge transport. This is explained by anion replacement, exclusion and the change of the charge transport mechanism.
The application of abrasive stripping voltammetry for a simple and rapid screening of pesticides
Authors: Jayarama Reddy S. , Hermes Michael , Scholz Fritz 
Published: May 2005

AbstractAbrasive stripping voltammetry has been employed to describe a simple and rapid solid‐state voltammetric procedure for the screening of pecticides. A particular case of chlorothion studied on cucumber and lettuce is discussed in this communication. The procedure described provides a semiquantitative assessment and obviates the need to bring the substrate into solution.
A peak current – scan rate relationship in staircase voltammetry of a surface redox reaction
Authors: Komorsky‐Lovrić Šebojka , Lovrić Milivoj 
Published: May 2005

AbstractStaircase voltammetry of surface redox reactions is characterized by a “quasireversible maximum”. The relationship between peak currents and scan rates is not linear, except for totally irreversible reactions, and the response may entirely vanish if the reaction is fast and reversible. For surface redox rections, the equivalence of staircase and linear sweep voltammetries can not he obtained by the variation of the current sampling fraction.
Iodide sensitive sensor based on a supported bilayer lipid membrane containing a cluster form of carbon (fullerene C60)
Authors: Wang Lei‐Guang , Wang Xing , Ottova Angelica L. , Ti Tien H. 
Published: May 2005

AbstractThe iodide ion sensitivity of a solid‐supported bilayer lipid membrane (s‐BLM) containing buckminsterfullerene(C60) as an electron mediator has been investigated using the cyclic voltammetry technique. We have shown that C60 in a lipid bilayer environment produces a unique and simple system for the detection of iodide. The sensitivity of C60‐containing s‐BLM to I− is excellent with a linear response in the range from 10−8 to 10−2 M. The use of fullerene C60‐doped s‐BLMs as sensors and devices for detecting other species is proposed.
Direct electrochemistry of hemoglobin at a bare silver electrode promoted by cetyl pyridinium chloride and its application in analysis
Authors: Ye Baoxian , Zhou Xingyao 
Published: May 2005

AbstractThe electrochemical redox of hemoglobin at a bare silver electrode promoted by cetyl pyridinium chloride with the cyclic voltammetric technique has been studied. The electrode reaction exhibits such good stability that the peak currents change less than 8.5% (oxidation) and 10.2%(reduction) for a continuing scan of 30 min in a solution containing 1 × 10−7mol/L hemoglobin. The electrode reaction rate constant Ks is 0.0865s−1 with a single electron transfer. Moreover, both the oxidation currents and the reduction currents are linear with the concentration of hemoglobin over the range of 1 × 10 −8−5 × 10−7mol/L. So, it can be used as an analytical method of determining hemoglobin.
Catalytic voltammetric determination of molybdenum at a chemically modified carbon paste electrode
Authors: Gao Zhiqiang , Siow Kok Siong , Ng Adeline 
Published: May 2005

AbstractTrace amounts of molybdenum can be determined in an acetate buffer solution (pH 2.6) containing chlorate, after the accumulation of molybdenum on a α‐benzoinoxime modified carbon paste electrode, coupled with the catalytic effect on the reduction of chlorate. Under optimized conditions, the catalytic voltammetric procedure gives a detection limit of 20 nmol L−1 molybdenum (60s accumulation). Most of the ions investigated did not interfere with the determination of molybdenum except for stannous ion. The catalytic peak current increases linearly with molybdenum concentration between 0.1 and 80 μmolL−1 with a correlation coefficient of 0.997 and a current sensitivity of 2.13 μA/μmol L−1. The chemically modified carbon paste electrode also displays good reproducibility with a relative standard deviation of 6.4 % for 20 repetitive determinations of 5.0 μmol L−1 molybdenum solutions.
Selectivity of liquid membrane ion‐selective electrodes
Authors: Bakker Eric 
Published: May 2005

AbstractThe current status of describing the selectivity of liquid membrane ion‐selective electrodes (ISEs) is reviewed. For ISEs that show Nernstian response toward all measured ions, the mixed ion response can often be described rigorously by a newly developed model that establishes required Nikolskii coefficients for a given target application. For ions of different charge, these obtained values are significantly different than predicted using the traditional Nikolskii–Eisenman equation. In contrast, for ISEs that show non‐Nernstian responses toward highly discriminated ions, two different procedures are recommended, depending on the scope of the experiment. Selectivities obtained with the so‐called matched potential method yield information about the apparent selectivity behavior of ISEs in real‐world samples, irrespective of theoretical expectations, but can, for the very same reason, generally not be used to predict the empirical selectivity for different analytical situations. On the other hand, experimental procedures are presented that allow for the determination of fundamental Nikolskii coefficients of such membranes, i.e., Nernstian slopes can now often be obtained by carefully adjusting the experimental conditions. Such values more closely reflect the ion extraction behavior of the membrane and can be used for characterization and optimization purposes. Each of the procedures has its validity and the respective values should preferably be reported simultaneously.
The use of ultrasound in the enhancement of the deposition and detection of metals in anodic stripping voltammetry
Authors: Marken Frank , Rebbitt Thomas O. , Booth Jonathan , Compton Richard G. 
Published: May 2005

AbstractThe fast electrochemical deposition of both mercury and amalgam films, a crucial step in analytical anodic stripping voltammetry, is demonstrated to occur in the presence of power ultrasound emitted from an immersion horn probe which was placed opposite the working electrode in a conventional three electrode cell. Due to considerably enhanced mass transport the rate of deposition is strongly increased compared to ‘silent’ conditions. The total amount of mercury adhering to a glassy carbon electrode surface, however, is limited to a ‘thin film’ of microscopically small droplets of mercury as shown by atomic force microscopy and voltammetry. Due to surface forces induced by ultrasound, abrasion of some of the deposit occurs and after a certain period of time the parallel electro‐deposition and abrasion processes reach a ‘steady state’.The deposition of mercury in the presence of Pb2+ or Cu2+ results in the formation of an amalgam and well‐defined, very sharp ‘stripping’ responses for the oxidation process of the corresponding amalgam were detected. The merit of insonation in analytical electrode preconcentration techniques is dicussed.
Determination of thallium in environmental samples using potentiometric stripping analysis. Method development
Authors: Švancara Ivan , Ostapczuk Peter , Arunachalam Jayaraman , Emons Hendrik , Vytřas Karel 
Published: May 2005

AbstractA method employing computerized potentiometric stripping analysis has been developed in order to determine trace levels of thallium in various environmental samples. The method is based on the preconcentration of T1 onto a mercury film electrode (formed in situ) with a subsequent reoxidation of amalgamated T1. A deaeration of the solution as well as the use of EDTA have resulted in a significant improvement of the sensitivity. In a supporting electrolyte containing 0.02–0.07 M HNO3 + 0.02 M CH3COONa + 0.001 M EDTA + 6 × 10−5 M HgCl2, the analytical signal versus concentration dependence is linear from 9 × 10−11 to 2.5 × 10−8 M T1 (preconcentration time from 5 to 30 min). A detection limit of about 5 × 10−11 M T1 (0.01 μg/L) is achieved when using preconcentration for 30 min. Despite a relatively high acidity of the supporting electrolyte used (pH 1.0–2.5), EDTA is capable to suppress the interferences from PbII ions up to a 500‐fold excess in concentration and from CdII and CuII up to their 100‐fold excess, respectively. Nitric acid has been incorporated into the supporting electrolyte as its constituent in order to determine T1 directly in the samples decomposed by means of high pressure ashing. The applicability of the method is demonstrated on various samples such as tap water (spiked), rain water, river sediment or sewage sludge. The results agree well with those obtained by isotope dilution‐mass spectrometry. The method has also been tested to determine T1 in digested biological samples (e.g., pine needles, poplar leaves and mussel tissues).
Study on diffusion of electroactive species in polyelectrolyte polyethylene glycol lithium perchlorate by chronoamperometry at a microdisk electrode
Authors: Zhou Huafang , Che Guangli , Dong Shaojun 
Published: May 2005

AbstractThe mass transport dynamics of ferrocene in polyelectrolyte polyethylene glycol lithium perchlorate (PEG · LiClO4) was studied by using chronoamperometry at a microdisk electrode. Chronoamperometry is a powerful method for the study of mass transport in polyelectrolyte, it has many advantages over the conventional methods at a microelectrode and the steady‐state method at an ultramicroelectrode. By using this method the apparent diffusion coefficient Dapp and concentration Ca of the electroactive species, can be estimated from a single experiment without previous knowledge of either one. We have estimated Dapp and Ca of ferrocene in PEG · LiClO4 polyelectrolyte from 25°C to 75°C. The dependence on the concentration of electroactive species was observed. The diffusion coefficients decrease with increasing ferrocene concentration and decreasing temperature. The mass transport mechanism is explained by using a free volume model.
Comparison of the voltammetric behavior of metronidazole at a DNA‐modified glassy carbon electrode, a mercury thin film electrode and a glassy carbon electrode
Authors: Brett Ana Maria Olivira , Serrano Silvia H. P. , Gutz Ivano G. R. , La‐Scalea Mauro A. 
Published: May 2005

AbstractThe electroanalytical performance at three electrodes: DNA‐modified galssy carbon electrode, mercury thin film electrode and glassy carbon electrode, for the study of the electrochemical reduction of metronidazole is compared. All three electrodes showed a similar trend in the reduction mechanism for metronidazole, depenent on pH in the acid and neutral region and independent in alkaline media, although there was a shift in the peak potentials to more negative values when a bare glassy carbon electrode was used compared to the other two. Besides the advantage of using a solid electrode for the reduction of metronidazole, the DNA‐modified galssy carbon electrode enables a lower detection limit of 1.0 μM owing to the preconecentration of the drug on the electrode surface, which is not the case for the mercury thin film or bare glassy carbon electrodes.
Amperometry and cyclic voltammetry of tyrosine and tryptophan‐containing oligopeptides at carbon fiber microelectrodes applied to single cell analysis
Authors: Paras Charina D. , Kennedy Robert T. 
Published: May 2005

AbstractThe amperometric and cyclic voltammetric detection of α‐melanocyte stimulating hormone (MSH), β‐endorphin, and corticotropin‐like intermediate lobe peptide (CLIP), all proopiocortin (POC) derived peptides secreted from melanocytes of the pituitary intermediate lobe, at carbon fiber microelectrodes was investigated. For amperometry, it was found that all of these peptides could be detected; however, fouling of the electrodes reduced the response of the electrode after successive application of the peptide in flow injection experiments. The fouling was apparently due to oxidation of tyrosine in the peptides as similar results were found for tyrosine but not tryptophan. The effect of fouling could be reversed if the electrode was electrochemically treated by scanning from −1.0 V to +1.0 V at 300 V/s for 2 min between application of the peptides. Using cyclic voltammtery at 800 V/s, it was possible to distinguish MSH, which had a peak shaped voltammogram, from the other POC peptides, which had relatively flat voltammetric waves at this scan rate. The scan rate dependence of the peak current for MSH revealed that the voltammetry was adsorption controlled. As a result, in a monitoring application, where voltammograms are continuously obtained with a fixed interval between them, decreasing the interval increases the temporal resolution but decreases the sensitivity for MSH. It was found that when monitoring the current in the potential range of 0.90 to 1.00 V, the temporal response to MSH was dependent upon the potential window used for scanning. Using high scan rates and a potential window 0 to 1.2 V, it was possible to monitor exocytosis from single melanocytes and use the voltammogram to demonstrate detection of MSH from the cells.
Electroanalytical determination of peroxidases and laccases on carbon paste electrodes
Authors: Kulys Juozas , Drungiliene Alma , Wollenberger Ulla , Krikstopaitis Kastis , Scheller Frieder 
Published: May 2005

AbstractElectrocatalytical reduction of hydrogen peroxide and oxygen was performed by horseradish peroxidase, recombinant Coprinus cinereus peroxidase, Polyporus pinsitus laccase and Botrytis cinerea laccase on carbon paste electrodes containing a paraffin soluble mediator. The electrocatalytical process proceeded at 0.0V (vs Ag/AgCl; in situ electrode). The electrode responses had maximum values at pH 6.4 and 5.5 for the horseradish peroxidase and laccases catalyzed reactions, respectively. The sensitivity for horseradish peroxidase and recombinant Coprinus cinereus peroxidase was 23.4 and 5.4 μC nM−1 cm−2, respectively. A detection limit of 7.5 fmol horseradish peroxidase could thus be achieved. Systems based on laccases showed lower sensitivity. The model of electrocatalytical reduction of hydrogen peroxide and oxygen included a permanent liberation of mediator from the carbon paste and it's biocatalytical conversion in the diffusion layer. The model was analyzed by comparing kinetic data in homogeneous solution with the electrode response. Mass transport effects were studied by using rotating carbon paste electrodes.
Voltammetry study of zeatin in a carbon fiber ultramicroelectrode. Determination by adsorptive stripping
Authors: Hernández Pedro , Paton Fernando , Ballesteros Yolanda , Hernández Lucas 
Published: May 2005

AbstractThe adsorptive stripping voltammetric determination of zeatin at a carbon fiber electrode is optimized and characterized. Applicability to assays of vegetable extracts is illustrated.