bluuebunny/crossref_metadata_2025_split huggingface dataset:
Removal of oxygen in flowing solutions using a photochemical process
Authors: Barisci Joseph N. , Wallace Gordon G. 
Published: May 2005

AbstractA method for the on‐line removal of dissolved oxygen has been developed and applied to the determination of metals by anodic stripping voltammetry in flowing solutions. The removal of oxygen results from a photochemical reaction between the supporting electrolyte and oxygen, induced by ultraviolet light directed into the detector flow cell. Organic acids such as citric, formic, and oxalic acids have been used as supporting electrolytes. Citric acid was found to be the most efficient oxygen scavenger. The removal of oxygen with this acid was also more efficient than conventional removal with nitrogen gas. The determination of Cu, Cd, and Pb was used to demonstrate the method.
Adsorptive stripping square‐wave voltammetric behavior of the enzyme adenosine deaminase
Authors: Flores Juana Rodríguez , Alvarez José María Fernández 
Published: May 2005

AbstractThe adsorptive stripping voltammetric behavior of adenosine deaminase has been studied by both square‐wave and differential pulse modes, leading to analytical methodologies for its determination in aqueous samples. The application of a square‐wave mode for the stripping of adsorbed adenosine deaminase has proved to be much more sensitive, yielding signals 50 times larger than those obtained by applying a differential pulse scan. The precision obtained for both voltammetric methods, at a concentration level as low as 8 ppb of the enzyme, was shown to be 2.47% (r.s.d., n = 7) and 2.28% (r.s.d., n = 7), respectively.
Construction and application of an all‐solid‐state chlorphenigramine ion‐selective electrode
Authors: Qu Aiying , Xu Dafeng , Ren Lixin , Jin Xinglian , Cai Shengmin 
Published: May 2005

AbstractUsing chlorpheniramine‐silicotungstate or chlorpheniramine‐ phosphotungstate ion‐pair complexes as active materials and graphite rods as substrates, all‐solid‐state chlorpheniramine ion‐selective electrodes were prepared. The effects of various factors on the performance of these electrodes were studied in detail. The electrodes exhibited a Nernstian range from 10−2‐10−5 M, with a slope of 58 mv/decade, and were much better than the previously reported PVC membrane chlorpheniramine ion‐selective electrodes Satisfactory results were obtained by using the prepared electrode to analyze chlorpheniramine containing samples.
Identification of photochemical products of amino acids, peptides, and proteins in on‐line, postcolumn photolytic derivatization detection by HPLC‐electrochemistry
Authors: Dou Lin , Krull Ira S. 
Published: May 2005

AbstractIn previous studies we have developed a method for the electrochemical detection of aromatic amino acids, sulfur‐containing amino acids, peptides, and proteins in HPLC by using photolytic derivatization approaches. Upon irradiation, nonelectroactive (or even inherently electroactive) amino acids and peptides can be converted to electroactive (or more electroactive) compounds, in an on‐line, postcolumn manner, which can be detected electrochemically in HPLC. In the case of proteins, the same method can be used to change the electroactivity of proteins photochemically. It is important to identify these photochemically converted compounds, especially those which are electroactive, in order to understand the detection mechanisms of the method. In this paper the results of identification of electroactive photoproducts for aromatic amino acids, peptides, and proteins are presented. Mainly, these studies were carried out by HPLC and direct electrochemical detection of off‐line photolyzed analytes.
Voltammetry in static and flowing solutions with a large‐amplitude sine wave potential
Authors: Long John T. , Weber Stephen G. 
Published: May 2005

AbstractVoltammetric detection is a potentially powerful method of detection for high performance liquid chromatography and flow injection analysis. A problem that needs a solution is its inferior detection limit compared to that obtained with amperometric detection. The shape of the potential waveform has been investigated in the search for methods of improving the detection limit of voltammetric detection. As a result, large amplitude sine wave potential perturbations have been found to give improved signal‐to‐noise ratios when compared to the values found for a corresponding triangle waveform (by a factor of from 1.1 to 5). This is principally due to the fact that the background current from a large amplitude triangle perturbation is spread over a wider frequency region. Signal processing techniques such as digital filtering have also been investigated. Digital bandpass filtering can be used to improve the signal to noise ratio by a factor of 2–13. Qualitative information (e.g., half‐wave potential) is obtained through observing the phase angle at harmonics of the fundamental frequency.
Photoelectrochemical detection of alcohols
Authors: Barisci Joseph N. , Wallace Gordon G. 
Published: May 2005

AbstractA method for photoelectrochemical detection of alcohols in liquid chromatography and flow injection analysis based on the reaction of the analyte with a photosensitized quinone (benzoquinone) has been developed. Irradiation of the flowing solution and electrochemical detection of the generated photoproduct is carried out within the detector flow cell. Pulsed amperometric detection produced higher sensitivities than conventional potentiostatic amperometry. Samples of vodka and beer were successfully analyzed using the proposed method.
Micro‐volume extraction for differential‐pulse voltammetric determination of iron in biological materials
Authors: Nagaosa Yukio , Bond A. M. 
Published: May 2005

AbstractA method based on separation by gas‐stirred extraction and differential‐pulse voltammetric detection of Fe(III) (0.50–8.0 μg) as the N‐phenylbenzohydroxamic acid complex in an ethyl acetate/acetonitrile phase (approximately 300 μ1) with a newly designed microcell provides sufficient sensitivity for its determination in biological materials. In the extraction and oxygen removal steps, nitrogen gas is passed through the aqueous and organic phases with a glass capillary. The proposed technique has been successfully applied to bovine liver and control serum.
Unsegmented flow systems as interfaces between samples and electrochemical detectors
Authors: de Castro M. D. Luque 
Published: May 2005

AbstractThe state‐of‐the‐art in the use of electrochemical detectors in unsegmented flow systems in general, and flow injection analysis (FIA) in particular, is presented. The different ways in which unsegmented flow systems can help to improve the performance and scope of electrochemical detectors (e.g., facilitating automation and miniaturization, allowing the on‐line implementation of continous separation techniques and multidetermination methods) are discussed. Current trends in this context are also covered.
Complexes of hydroxamates VIII. The affinity of methioninehydroxamic acid for mixed metal complexation potentiometric and polarographic studies
Authors: Marafie Hayat M. , Makhyoun Mohamed , Al‐Salem Najeeb , El‐Ezaby Mohamed S. 
Published: May 2005

AbstractBinary metal complexations of Ni(II), Cu(II), and Zn(II) with methionine‐hydroxamic acid (MX) were studied potentiometrically at 37°C and μ = 0.15 M NaCl. The mixed metal complexes with MX, (MXCu(II)Zn(II), and MXNi(II)Zn(II)) were also studied under the same conditions. The ternary enhancement was discussed in terms of the binary complex formation. In addition, the binary and ternary systems were studied by differential pulse polarography and the behavior of the reduction properties of the different ternary species were correlated with those of the simple metal ions and the binary species.
Channel electrode voltammetry: Thin‐layer effects and the shape of quasi‐reversible current‐voltage curves
Authors: Compton Richard G. , Wellington R. Geoffrey 
Published: May 2005

AbstractA computational approach to the calculation of irreversible and quasi‐reversible current voltage curves at channel electrodes is presented. The method has generality since, in particular, no assumptions are made as to the electrode geometry or electrolyte flow rates so that both Lévěque and, with novelty, thin‐layer conditions may be explored. An approximate analytical theory for the shape of current‐voltage curves which predicts the flow rate dependence of the half‐wave potential is presented for the latter case and found to be in good agreement with rigorous computational theory.
The anodic oxidation of hydrazine on glassy carbon electrode
Authors: Wang Baochen , Cao Xueqiang 
Published: May 2005

AbstractThe anodic oxidation kinetics of hydrazine (N2H4) on glassy carbon (GC) electrode was examined by cyclic voltammetry, rotating disk and ring‐disc electrode techniques. The possible mechanisms of N2H4 oxidation in both aqueous and nonaqueous solutions are proposed.
Determination of alkaloids by differential pulse polarography. III Corydalis alkaloids
Authors: Temizer H. , Sener B. , Temizer A. , Kir S. 
Published: May 2005

AbstractThe Corydalis alkaloids have been investigated by differential pulse polarography as part of our continuing study of alkaloids. In this study, the alkaloidal content of Corydalis solida (L.) subsp. solida was determined. The results were compared by their structure and reduction mechanism. Quantitative analysis illustrates that Corydalis alkaloids can be determined down to sub‐ppm level using differential pulse polarography in Britton‐Robinson buffer pH 10. The amount of the various alkaloids in Corydalis solida (L.) subsp. solida have been shown. It was concluded that the reduction process at the dropping mercury electrode was catalytic in nature.
Voltammetric study of zinc(II) and lead(II) ions in the presence of alginate and pectin
Authors: Ariño Cristina , Nadal Anna Maria , Esteban Miquel , Casassas Enric 
Published: May 2005

AbstractComplex formation of Zn(II) and Pb(II) with alginates and pectins was studied by normal‐pulse (NPP), reverse‐pulse (RPP), and differential‐pulse polarography (DPP), cyclic voltammetry (CV), and differential pulse anodic stripping voltammetry (DPASV). The systems appear to be labile on the different time scales of the various techniques. Adsorption of both polysaccharides, and the further induced adsorption of Zn(II) and Pb(II), are evidenced clearly by NPP. On the other hand, induced adsorption of metal ions is minimized under the RPP conditions. The reversibility of the redox couples Zn2+/Zn(Hg) and Pb2+/Pb(Hg) is not strongly affected by the presence of polysaccharides. Titrations of Zn(II) and Pb(II) with alginates or pectins were carried out by DPP and DPASV in order to determine formation constants, which was only found for the Zn(II)‐ion systems.
Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part II: Polarographic and voltammetric reduction of some nitramines, pyrazolium, and imidazolium nitro derivatives
Authors: Dumanović D. , Jovanović J. , Sužnjević D. , Erceg M. , Zuman P. 
Published: May 2005

AbstractReduction of 1‐nitropyrazole (I) results in acidic media in a cleavage of the NN bond and formation of nitrous acid which is further reduced at more negative potentials. At pH > 4 a competitive reduction of the nitramine to nitrosamine occurs. Four‐electron reduction of nitro derivatives of pyrazolium (II) and (III) and imidazolium (IV) and (V) salts results in a formation of a hydroxylamine derivative. The reduction follows the scheme: H+, e, e, H+, 2e, 2H+. In the reduction product the azolium ring is reduced at more negative potentials. Whereas the effect of pyrazolium and imidazolium rings on the reducibility of the nitro group is comparable, the interaction between the nitro group and the azolium ring markedly depends on the position of the nitro group on the ring.
Potentiometric detectors for the determination of acidity by discontinuous flow analysis
Authors: Cardwell Terence J. , Cattrall Robert W. , O'Connell Gregory R. , Petty John D. , Scollary Geoffrey R. 
Published: May 2005

AbstractThree potentiometric detectors, each incorporating a vibrating reed mixer, were investigated for use in the determination of acidity by discontinuous flow analysis (DFA). Two of these used PVC and glass membrane pH‐sensors, and the third employed a novel differential titration technique based on two quinhydrone electrodes. These detectors were applied to the determination of the total acidity of vinegars and the titratable acidity of wines, the results agreeing well with standard procedures. The analysis of wine proved to be difficult because of the gradual change in pH at the end‐point and so a method was developed which determined the titratable acidity at pH 8.3.
Cathodic stripping voltammetry of vanadium based on adsorptive accumulation of its solochrome violet RS complex at the static mercury drop electrode
Authors: Farias Pércio A. M. , Takase Iracema 
Published: May 2005

AbstractA very sensitive electrochemical stripping procedure for vanadium is reported. Accumulation is achieved by controlled adsorption of the vanadium/solochrome violet RS complex on the static mercury drop electrode. Optimal experimental parameters found include an accumulation potential of −0.22 V, solochrome violet RS concentration of 2.0 × 10−6M, and a differential pulse stripping mode. After 5 minutes preconcentration, a detection limit near 1.7 × 10−10 M vanadium is obtained. The response is linear over the 0–21 μg1−1 concentration range, and the relative standard deviation (at the 11.2 μg1−1 level) is 3.8%. The possible interference by other trace ions are investigated. Simultaneous determination of vanadium with molybdenum and cadmium is illustrated. The merits of this procedure are demonstrated in the analysis of sea and river waters.
Electrochemical methods for food and drink analysis
Authors: Mannino Saverio , Wang Joseph 
Published: May 2005

AbstractThis review article assesses the status of electroanalysis in the food industry. Modern trends in electroanalysis, which offer unique possibilities for assays of foods and drinks, and for monitoring food production processes, are discussed. Particular attention is given to the utility of new biocatalytic sensors, stripping techniques, and electrochemical flow detectors in the food industry. More than 90 references are given and future prospects are discussed.
Double‐layer capacitance measurements of self‐assembled layers on gold electrodes
Authors: Świetlow Aleksander , Skoog Mikael , Johansson Gillis 
Published: May 2005

AbstractThe double‐layer capacitance of self‐assembled unsubstituted and ω‐substituted n‐alkanethiol layers on gold electrodes was studied using a potential step technique. A four‐element equivalent circuit model was used for the evaluation of the current response. The double‐layer capacitance and the conductivity were both found to decrease with increasing chain length for alkanethiol homologues. Substitution with COOH, OH, and NH2 in the ω‐position caused the double‐layer capacitance to rise dramatically, whereas the general pattern of decreasing capacitance with increasing chain length was confirmed for a series of homologue ω‐mercaptoalcohols. The effect of polar substituents is explained by the introduction of permanent dipoles into the self‐assembled layers. The capacitance was independent of the applied potential for dodecanethiol but increased with voltage for butanethiol when tested in the range of −200 to 500 mV versus Ag/AgCl. Buffer strength had little influence on the double‐layer capacitance above 5 mM (phosphate buffer, pH 7.0). The self‐assembly of mercaptoethanol was completed within 3 minutes from an aqueous solution and that of alkanethiols within 10 minutes using acetone solutions. The electrodes were stable for at least several hours.
Potentiometric monitoring of proteins: Part 5. A voltammetric study of copper electrodes
Authors: Hitchman Michael L. , Trojanowicz Marek 
Published: May 2005

AbstractA voltammetric study has been made of copper electrodes in the presence and absence of amino acids and proteins. The results are discussed in terms of oxide formation on the copper surface and the complexation of the biomolecules with the copper. It is shown that in the presence of strongly complexing ligands, the copper surface is effectively self‐cleaning, and reproducible potentiometric results can be obtained without any rigorous electrode precleaning procedures. In the presence of weakly complexing ligands, on the other hand, it is shown why it is necessary to reduce the electrode surface beforehand in order to carry out reproducible potentiometry.
A finite‐element method for determining ohmic distortion of current‐voltage curves at hydrodynamic electrodes
Authors: Coles Barry A. , Compton Richard G. , Spackman R. Anthony 
Published: May 2005

AbstractA finite‐element method is described that predicts the effects of ohmic distortion of current‐voltage curves for arbitrary cell and hydrodynamic electrode geometries using the widely available circuit analysis program SPICE. Simulated and experimental data are presented for a channel electrode flow cell showing the displacement of the half‐wave potential and the potential‐dependent error in the Tafel slope for the case of an electrochemically reversible electrode reaction. Error curves are provided that may be scaled for different electrolyte conductivities as a guide to the maximum current levels that may be used in practice. For analytical flow detection work, the displacement of the half‐wave potential under certain conditions implies that high detection potentials must be used to obtain the correct concentration‐related current intensity. The implications for quantitative measurements using practical electrodes are assessed.
Polarographic and electrochemical studies of some aromatic nitro compounds: Part VII. Polarographic, voltammetric, and controlled potential electrolytic reduction of meta‐ and para‐nitrobenzaldehyde
Authors: Fijalek Zbigniew , Pugia Michael , Zuman Petr 
Published: May 2005

AbstractIn acidic media, at pH < 7, the nitro groups in both meta‐ and para‐nitrobenzaldehyde are reduced in a four‐electron process and form corresponding formylhydroxylamines. These species are reduced in protonated forms to corresponding formylanilines, which are further reduced in two‐electron steps to alcohols. At pH > 7, the formylhydroxylamine condenses rapidly to form a nitrone, which is further reduced to two two‐electron steps, for the derivative of meta‐nitrobenzaldehyde overlap. The addition of ortho‐ to para‐nitrobenzaldehyde results in cross‐condensation.
Highly sensitive electrochemical sensor for ozone in water using porous carbon felt electrode
Authors: Uchiyama Shunichi , Ikarugi Takao , Mori Masayuki , Kasama Kaname , Ishikawa Yoichi , Kaneko Mitsunori , Umezawa Akira 
Published: May 2005

AbstractA novel electrochemical sensor with a [polytetrafluoroethylene] (PTFE) membrane (10% voids) and a porous carbon felt electrode has been fabricated for the determination of residual ozone in water. The carbon felt has a large specific surface area which can capture all of the ozone transferred from the sample solution through a PTFE membrane, and an extremely low concentration of ozone (about 0.5 ppb) can be detected. The relationship between the current response and the ozone concentration obtained by the Indigo method was linear over the range 5–800 ppb. The sensitivity was calculated to be approximately 10 μA/(ppm cm2) at 12°C. The relative standard deviations (RSDs) of the response currents were below 5% when the ozone concentration was higher than 50 ppb. The response to 1 ppm residual chlorine is about 1.3% of that of the same concentration of ozone in solution at pH 5. The measured current was reproducible over three months and was found to be suitable for use as an on‐line sensor.
The effect of complexation equilibria on the response of chemically modified electrodes for the determination of silver
Authors: Labuda Ján , Vaníčková Mária 
Published: May 2005

AbstractThe determination of silver using anodic stripping voltammetry at graphite electrodes modified with various macrocyclic thia ligands and a Nafion film was examined in different media. The electrode response is proportional to the stability constant of the silver complex with the immobilized thia ligand. In the presence of cyanide or thiosulfate ions in the silver solution, the signal is diminished according to the concentration of the foreign ligand and the value of the corresponding conditional stability constant. The effect of the accumulation time on the detected fraction of silver is reported, and the consequences for speciation studies are indicated.
Catalytic reduction of benzoquinone at polyaniline and polyaniline/enzyme films
Authors: Cooper Julia C. , Hall Elizabeth A. H. 
Published: May 2005

AbstractThe enzyme‐mediator‐conducting polymer model provides a convenient charge transporting immobilization matrix for redox enzymes in potential biosensor constructions. This study considers the charge transport mechanism in the benzoquinone (Q)‐polyaniline (Pani) system. An enhanced current can be obtained on Pani, compared with Pt, using Q as enzyme mediator. Two‐electron redox pathways are available for the Q/H2Q (hydroquinone) system, but the kinetics limit this conversion. On Pt, one‐electron equivalent is estimated. On Pani‐modified electrodes, reduction of Q on Pani is a nearly reversible two‐electron process at stationary electrodes at low pH. At rotating electrodes, the initial reaction occurs at the surface of the polymer at pH 1.1, but the second electron transfer is prevented by loss of the intermediate from the surface before it can migrate into the film. At stationary electrodes, the H2Q product is stabilized, possibly by the formation of a charge‐compensating complex between the H2Q anion/radical and the polymer. At higher pH, charge transfer through the polymer is slow and no reduction of Q occurs on the outside of the film, instead occurring in a layer at the electrode limited by the exchange kinetics there. Promotion of the two‐electron pathways on Pani is proposed as the source of current enhancement when Q is employed as an enzyme mediator.
Amperometric biosensing of alcohols at electrochemically pretreated glassy‐carbon enzyme electrodes
Authors: Wang Joseph , Gonzalez‐Romero Elisa 
Published: May 2005

AbstractSubstantial improvements in the performance of amperometric biosensors for alcohols are achieved by subjecting the glassy carbon transducer to an electrochemical pretreatment prior to the immobilization of alcohol dehydrogenase. The enzymatically generated dihydronicotinamide adenine dinucleotide (NADH) can thus be detected at a substantially (∼340 mV) lower potential compared to the untreated surface. Hence, highly sensitive low‐potential amperometric sensing of alcohols is accomplished without the assistance of a surface‐bound electron mediator. Applicability to alcoholic beverages is illustrated.
Comparison of detector cell configurations in flow‐injection potentiometry
Authors: Davey David E. , Mulcahy Dennis E. , O'Connell Gregory R. 
Published: May 2005

AbstractA comparative assessment has been made of three detector cell configurations, flow‐through, wall jet, and edge jet, based upon the flow‐injection performance of a solid‐state iodide‐selective electrode. Several aspects of the observed behavior have been explained with reference to flow patterns visualized by intercalation of Eriochrome T indicator into the flow stream and filmed under high magnification. The edge jet, a thin‐layer design incorporating an inlet channel at 45° to the sensing surface of the electrode, performed well over a considerable range of cell volumes, while the wall‐jet and flow‐through arrangements were prone to flow instability at higher volumes, resulting in irregular peak profiles and irreproducible baseline recovery times. Best response and recovery were recorded for all three cells when the distance between the inlet nozzle and the electrode membrane did not exceed 1.0 mm.