bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization and Optimization of Interdigitated Ultramicroelectrode Arrays as Electrochemical Biosensor Transducers
Authors: Min Junhong , Baeumner Antje J. 
Published: March 2004

AbstractInterdigitated ultramicroelectrode arrays (IDUAs) were fabricated on glass wafers and investigated to obtain optimal oxidation and reduction reactions of potassium ferro/ferrihexacyanide, Fe2+/3+(CN)6, when using a 2‐electrode set up. These electrodes will be used as transducers in portable microfluidic‐based biosensors in the future for the detection in an aqueous, biocompatible matrix. IDUAs were designed to maximize the signal‐to‐noise ratio (S/N) investigating electrode height, gap size, finger width, and material. Interesting differences in the electrode materials gold and platinum were found, which were due to the oxidization of platinum and gold during the IDUA fabrication process. It resulted in gold IDUAs being by far superior in respect to signal‐to‐noise ratio and overall signal magnitude to those made of platinum. The effects of gap size, electrode width and number of electrode fingers were as expected. Optimal electrode heights were in the range of 70 nm–140 nm, much larger and smaller electrodes had lower signal‐to‐noise ratios due to overall reduced signal or increased background. The optimized IDUA was made out of gold, had 400 fingers with a finger width of 2.7 μm, a finger height between 70 nm and 140 nm and a gap size of 0.9–1 μm. A detection limit of as low as 0.1 μM ferro/ferrihexacyanide measured in a simple 2‐electrode set up was obtained with a signal‐to‐noise ratio of 9.7.
Immobilization of Enzymes on the Nano‐Au Film Modified Glassy Carbon Electrode for the Determination of Hydrogen Peroxide and Glucose
Authors: Lei Cun‐Xi , Wang Hua , Shen Guo‐Li , Yu Ru‐Qin 
Published: March 2004

AbstractA new enzyme‐based amperometric biosensor for hydrogen peroxide was developed relying on the efficient immobilization of horseradish peroxidase (HRP) to a nano‐scaled particulate gold (nano‐Au) film modified glassy carbon electrode (GC). The nano‐Au film was obtained by a chitosan film which was first formed on the surface of GC. The high affinity of chitosan for nano‐Au associated with its amino groups resulted in the formation of nano‐Au film on the surface of GC. The film formed served as an intermediator to retain high efficient and stable immobilization of the enzyme. H2O2 was detected using hydroquinone as an electron mediator to transfer electrons between the electrode and HRP. The HRP immobilized on nano‐Au film maintained excellent electrocatalytical activity to the reduction of H2O2. The experimental parameters such as the operating potential of the working electrode, mediator concentration and pH of background electrolyte were optimized for best analytical performance of amperometry. The linear range of detection for H2O2 is from 6.1×10−6 to 1.8×10−3 mol L−1 with a detection limit of 6.1 μmol L−1 based on signal/noise=3. The proposed HRP enzyme sensor has the features of high sensitivity (0.25 Almol−1cm−2), fast response time (t90%≤10 s) and a long‐term stability (>1 month). As an extension, glucose oxidase (GOD) was chemically bound to HRP‐modified electrode. A GOD/HRP bienzyme‐modified electrode formed in this way can be applied to the determination of glucose with satisfactory performance.
Batch Injection Analysis: An Almost Unexplored Powerful Tool
Authors: Quintino Maria S. M. , Angnes Lúcio 
Published: March 2004

AbstractThe main purpose of this review is to report the development and potentialities of batch injection analysis (BIA) and call the attention of researchers about the power of this (until now) almost unexplored tool. The text focuses on the concepts and potentialities of BIA combined with other techniques for analytical purposes. The association of BIA with amperometry, potentiometry, voltammetry, calorimetry, fluorescence and spectrophotometry is presented and important aspects related with each technique are discussed. Some aspects comparing the similarities and differences between BIA, FIA and wall‐jet are presented along the text.
Voltammetric Elucidation of Ion Transfer Through an Extremely Thin Membrane
Authors: Ichieda Nobuyuki , Shirai Osamu , Yoshida Yumi , Maeda Kohji , Torimura Masaki , Kihara Sorin 
Published: March 2004

AbstractDigital simulation of the cyclic voltammogram for the ion transfer through a liquid membrane of thickness from 1 mm to 10 nm was performed. The magnitude of current and the shape of the voltammogram simulated for extremely thin membrane (10 nm thick) were similar to those observed experimentally with a bilayer lipid membrane, BLM, of about 10 nm in thick, when the diffusion coefficient of an ion in the BLM was assumed to be extraordinary small (10−13 to 10−14 cm2 s−1).
Immunosensors Based on Layer‐by‐Layer Self‐Assembled Au Colloidal Electrode for the Electrochemical Detection of Antigen
Authors: Wang Meijia , Wang Lianying , Yuan Hang , Ji Xiaohui , Sun Chunyan , Ma Lan , Bai Yubai , Li Tiejin , Li Jinghong 
Published: March 2004

AbstractColloidal Au particles have been deposited on the gold electrode through layer‐by‐layer self‐assembly using cysteamine as cross‐linkers. Self‐assembly of colloidal Au on the gold electrode resulted in an easier attachment of antibody, larger electrode surface and ideal electrode behavior. The redox reactions of [Fe(CN)6]4−/[Fe(CN)6]3− on the gold surface were blocked due to antibody immobilization, which were investigated by cyclic voltammetry and impedance spectroscopy. The interaction of antigen with grafted antibody recognition layers was carried out by soaking the modified electrode into a phosphate buffer at pH 7.0 with various concentrations of antigen at 37 °C for 30 min. Further, an amplification strategy to use biotin conjugated antibody was introduced for improving the sensitivity of impedance measurements. Thus, the sensor based on this immobilization method exhibits a large linear dynamic range, from 5–400 μg/L for detection of Human IgG. The detection limit is about 0.5 μg/L.
Determination of Cytochrome C with Cellulose – DNA Modified Carbon Paste Electrodes
Authors: Lee Tae‐Young , Kim Hwa‐Jeong , Moon Jeon‐Ok , Shim Yoon‐Bo 
Published: March 2004

AbstractA sensor for cytochrome c (cyt c) was developed using a carbon paste electrode (CPE) modified with cellulose‐DNA. Cyt c was adsorbed on the cellulose‐DNA modified CPE through the electrostatic interaction between them. Owing to this process, a pair of well‐defined peaks appeared at +48 mV/85 mV (Epc/Epa vs. Ag/AgCl). This property of the cellulose‐DNA modified CPE was utilized for the analysis of cyt c in a biological sample. The optimum experimental conditions for analysis were investigated and a calibration plot was obtained between 1.0×10−4 M and 1.0×10−6 M (±5% at n=5) at the optimized condition. The detection limit for cyt c at the optimized experimental condition was 5.0×10−7 M (S/N=3) for 30 min of deposition time with differential pulse voltammetry (DPV). The real sample analysis was carried out with the standard addition method to evaluate the developed method. The content of cyt c in total proteins of 80.0 mg/mL in rat mitocondria fractions was determined to be 0.12 (±0.02) mg/mL.
Flow‐Injection Amperometric Detection with Solvent Polymeric Membrane Ion Sensors
Authors: Ortuño Joaquín A. , Hernández Jorge , Sánchez‐Pedreño Concepción 
Published: March 2004

AbstractAn amperometric detector for hydrophobic ions based on a plasticized poly(vinyl) chloride (PVC) membrane incorporated in a flow‐injection system was developed. A four‐electrode potentiostat with ohmic drop compensation was used, while a flow‐through cell incorporated the four electrodes and the membrane, which contained tetrabutylammonium tetraphenylborate. When the influence of the applied potential and of the flow‐injection variables on the determination of tetrabutylammonium was studied, a linear relationship was observed between current peak height and ion concentration over a range of 5×10−6–6×10−5 M tetrabutylammonium. Good repeatability and between‐day reproducibility and high sample frequency were obtained. The effect of other ions was studied. Two different amperometric methods, indirect and direct, were also developed for the determination of dodecylsulfate in the concentration range 3×10−5–9×10−4 M.
Selective Determination of Uric Acid in Presence of Ascorbic Acid and Dopamine at Neutral pH Using Exfoliated Graphite Electrodes
Authors: Ramesh P. , Sampath S. 
Published: March 2004

AbstractExfoliated graphite electrodes have been used to detect uric acid at neutral pHs, by following its oxidation. A linear range of 5–53 μM and a detection limit of 5 μM are observed at a pH of 7.0. Uric acid was found to be selectively adsorbed on exfoliated graphite surface in the presence of excess ascorbic acid. This leads to its selective determination in the presence of ascorbic acid. Simultaneous detection of uric acid, dopamine and ascorbic acid has also been demonstrated on exfoliated graphite electrodes in a pH 7 buffer.
Electrocatalytic Oxidation of NADH by Oxidized s‐Adenosyl‐L‐Methionine (SAMe): Application to NADH and SAMe Determinations
Authors: de‐los‐Santos‐Álvarez Noemí , Lobo‐Castañón María Jesús , Miranda‐Ordieres Arturo J. , Tuñón‐Blanco Paulino 
Published: March 2004

Abstracts‐Adenosyl‐L‐methionine (SAMe) is an adenosine analogue with therapeutical activity against affective disorders and liver dysfunctions. It can be oxidized on graphite electrode yielding a strongly adsorbed electroactive oxidation product for which a quinone‐imine structure is proposed. This compound is capable of electrocatalyzing the NADH oxidation at low potentials, lowering the overvoltage by about 300 mV. An amperometric method for NADH determination at +0.1 V (Ag|AgCl|KClsat) is developed using an oxidized‐SAMe‐modified electrode in pH 9. Linear calibration plots were obtained with a detection limit of 2.4 nM. The electrode response time and the relative standard deviation of the slope of the calibration plot for 5 different modified electrodes were 12 s and 5.6% respectively. The catalytic scheme also provides the first method to determine SAMe itself by adsorptive differential pulse voltammetry. The linear range was found to be 42.4–424 nM with a reproducibility of 6.9%. The method was applied to SAMe determination in a pharmaceutical formulation.
Sonoelectroanalysis in Acoustically Emulsified Media: Zinc and Cadmium
Authors: Kruusma Jaanus , Tomčík Peter , Banks Craig E. , Compton Richard G. 
Published: March 2004

AbstractDithizone (diphenylthiocarbazone) dissolved in chloroform was employed as a ligand for the solvent extraction of either cadmium or zinc from aqueous media. Acoustic emulsification was shown to be effective both in extraction and recovery or ‘back extraction’ with a fresh clean aqueous solution. Quantitative analysis of cadmium or zinc removed via double sono‐extraction from aqueous media hostile to voltammetric analysis proceeded via sono‐square wave anodic stripping voltammetry (sono‐SWASV), resulting in high sensitivity in the relatively clean medium. This technique was shown to be viable for the quantification of cadmium from surfactant containing media where direct electroanalytical techniques fail. The method was also applied to the analysis of zinc in commercial shampoo and toothpaste, giving results in close agreement with those obtained from independent analysis. Biphasic sono‐extraction synergistically coupled with sono‐SWASV therefore presents an attractive technique for cadmium or zinc analysis in electrode passsivating media. The technique likely removes contaminants present in the test solution since these will ‘prefer’ to remain in the initial aqueous phase, or will transfer to the extracting organic phase, but are unlikely to be doubly transferred into the clean final aqueous phase.
Electrocatalytic Oxidation of Sulfite on a Cobalt Pentacyanonitrosylferrate Film Modified Glassy Carbon Electrode
Authors: Pournaghi‐Azar M. H. , Sabzi R. E. 
Published: March 2004

AbstractThe electrocatalytic oxidation of sulfite has been studied on the cobalt pentacyanonitrosylferrate modified glassy carbon electrode (CoPCNF). The CoPCNF films on the glassy carbon electrodes show an excellent electrocatalytic activity toward the oxidation of sulfite in 0.5 M KNO3. The kinetics of the catalytic reaction was investigated by using cyclic voltammetry, rotating disk electrode (RDE) voltammetry and chronoamperometry. The average value of the rate constant, K, for the catalytic reaction and the diffusion coefficient, D, were evaluated by different approaches for sulfite and found to be 2.9×102 M−1s−1 and 4.6×10−6 cm2s−1, respectively. At a fixed potential under hydrodynamic conditions (stirred solutions), the oxidation current is proportional to the sulfite concentration and the calibration plot was linear over the concentration range 5×10−6–1×10−4 M. The detection limit of the method is 3×10−6 M., low enough for the trace sulfite determination.
Determination of an Ethylene Bisdithiocarbamate Based Pesticide (Nabam) by Cobalt Phthalocyanine Modified Carbon Ink Electrode
Authors: Lin Meng Shan , Wang Jun Sheng 
Published: March 2004

AbstractA phthalocyanine based sensor, for anodic detection of sodium ethylene bisdithiocarbamate (Nabam) by coating a mixture of cobalt phthalocyanine (CoPC) modified carbon ink on the surface of a glassy carbon electrode, has been described. The modified ink was prepared by mixing three percent of cobalt phthalocyanine into carbon ink and then diluting the mixture with cyclohexanone in w/w ratio of 1/9. A suitable portion (or 1 μL) of ink mixture was then dip‐coated on a rotating disk glassy carbon electrode. The modified ink electrode was air‐dried for 15 mins before use. In comparison to the bare ink electrode on which the oxidation of Nabam takes place at 300 mV (vs. 3 M Ag/AgCl), the oxidation potential (−125 mV) of Nabam at the CoPC modified ink decreases significantly. A typical calibration plot of Nabam proportionally increases over the concentration range of 2.5 to 36 μM (R=0.9990). The detection limit is estimated about 28.8 nM (S/N=3) and its response time (between 10% to 90% of steady‐state response) is about 5.3 s at the injection of 5 μM Nabam. The sensitivity requirement of JMPR meeting (Joint FAO/WHO Meeting on Pesticide Residues) for ethylene bisdithiocarbamates (EBDCs) is achieved by this proposed scheme.
Electrochemical Detection of As(III) via Iodine Electrogenerated at Platinum, Gold, Diamond or Carbon‐Based Electrodes
Authors: Hignett Geraldine , Wadhawan Jay D. , Lawrence Nathan S. , Hung Dang Q. , Prado César , Marken Frank , Compton Richard G. 
Published: March 2004

AbstractThe reaction of iodine, electrogenerated from iodide, is used for the detection of As(III) via electrocatalytic reaction in the diffusion layer of a boron‐doped diamond electrode. The merits of this electrode material for this purpose (over platinum, gold or glassy carbon) are demonstrated and the kinetics of the reaction between I2 and As(III) in acid reported.
Dopamine and Glucose Sensors Based on Glassy Carbon Electrodes Modified with Melanic Polymers
Authors: González Rosa , Sánchez Alberto , Chicharro Manuel , Rubianes María D. , Rivas Gustavo A. 
Published: March 2004

AbstractThis work deals with the study of polymers electrogenerated from different catechols at glassy carbon electrodes and the analytical applications of the resulting modified electrodes for dopamine quantification and glucose biosensing. The electropolymerization was performed from a 3.0×10−3 M catechol solution (catechol, dopamine, norepinephrine, epinephrine or L‐dopa in a 0.050 M phosphate buffer pH 7.40) by applying 1.00 V for 60 min. The properties of the polymers are very dependent on the nature of the catechol, L‐dopa being the best. Glassy carbon electrodes modified with melanic polymers electrogenerated from L‐dopa and norepinephrine were found to be suitable for dopamine determinations in flow systems, although the behavior was highly dependent on the nature of the monomer. Detection limits of 5.0 nM dopamine and interferences of 9.0 and 2.6% for 5.0×10−4 M ascorbic acid and 5.0×10−5 M dopac, respectively, were obtained at the glassy carbon electrode modified with a melanin‐type polymer generated from L‐dopa (using 1.0×10−3 M AA in the measurement solution). The advantages of using a melanin‐type polymer generated from dopamine to improve the selectivity of glucose biosensors based on carbon paste electrodes containing Pt and glucose oxidase (GOx) are also discussed. The resulting bioelectrodes combines the high sensitivity of metallized electrodes with the selectivity given by the polymeric layer. They exhibit excellent performance for glucose with a rapid response (around 10 seconds per sample), a wide linear range (up to 2.5×10−2 M glucose), low detection limits (143 μM) and a highly reproducible response (R.S.D of 4.9%). The bioelectrodes are highly stable and almost free from the interference of large excess of easily oxidizable compounds found in biological fluids, such as ascorbic acid (AA), uric acid (UA) and acetaminophen.
Organic Redox Probes for the Key Oxidation States in Mixed Valence Ruthenium Oxide/Cyanometallate (Ruthenium Prussian Blue Analogue) Catalysts
Authors: Kumar Annamalai Senthil , Zen Jyh‐Myng 
Published: March 2004

AbstractThe electrochemical redox behavior of the polynuclear mixed valence ruthenium oxide cyanometallate complexes (mvRuOxMCN, M=Fe, Cr, Ni, Cu, Ru and Pt) have been systematically studied in this report by using three redox sensitive organic probes of glucose, ethanol and formaldehyde. The results were interpreted by the well‐established ruthenium oxide and Prussian blue chemistry. The mvRuOxMCN, under the category of Ru‐based Prussian blue analogue, was found to possess superior electrocatalytic activity than either ruthenium oxide or Prussian blue in acidic mediums. The electrogenerated oxy/hydroxy‐RuVII state (at +1.1 V vs. Ag/AgCl) was unusually stabilized in the mvRuOxMCN matrix without any disproportion reaction in acidic environments. In contrast to those of earlier studies, possible structure in terms of the RuIII/IINCMand RuIII/IIORuVII/VIsites was proposed here. Enzyme‐less analytical detection of glucose in acidic conditions was first time demonstrated with sensitivity comparable to that of ruthenium oxide‐based electrodes in alkaline solutions.
Electrochemical Properties of Lanthanum Hexacyanoferrate Particles Immobilized onto Electrode Surface by Au‐Codeposition Method
Authors: Eftekhari Ali 
Published: March 2004

AbstractLanthanum hexacyanoferrate (LaHCF) was immobilized onto a substrate surface as an electroactive material by Au‐codeposition method. The LaHCF particles were attached to the electrode surface as the result of occlusion within the gold film deposited. This deposition method was first introduced for the preparation of hexacyanoferrate‐based modified electrodes. It was demonstrated that this deposition method provides a higher stability of the electroactive film in comparison with available methods for the mechanical attachment of electroactive films. On the other hand, electrochemical properties of the LaHCF film modified electrode were studied for the first time. The results showed that LaHCF film has excellent electrochemical activity as well as other analogues of Prussian blue. The modified electrode was successfully used as an electrocatalyst for the oxidation of ascorbic acid.
Characterization of Carbon Film Electrodes for Electroanalysis by Electrochemical Impedance
Authors: Filipe Olga M. S. , Brett Christopher M. A. 
Published: March 2004

AbstractThe interfacial behavior of electrodes fabricated from carbon film resistors of 2 and 20 Ω in supporting electrolyte solutions of varying pH used in electroanalytical experiments has been characterized by electrochemical impedance spectroscopy with complementary cyclic voltammetric experiments. Equivalent circuits are proposed to fit the experimental data and the influence of electrode pretreatment has also been investigated.
Electroactive Ceramic Carbon Electrode Modified with Hydrophobic Polar Solvent
Authors: Shul Galyna , Saczek‐Maj Monika , Opallo Marcin 
Published: March 2004

AbstractCeramic carbon electrode modified with redox probe solution in hydrophobic polar solvent was prepared and studied. The electrode consisting of graphite powder, homogeneously dispersed in hydrophobic silicate matrix, was prepared from the mixture of methyltrimethoxysilane based sol and graphite powder by sol‐gel method. It was immersed in t‐butyloferrocene solution in nitrobenzene. The electrode properties were investigated by cyclic voltammetry and chronoamperometry in KNO3 solution of different concentration. In most cases linear polarization of the electrode towards positive potentials results in peak shaped voltammogram originating from electrooxidation of t‐butyloferrocene. Its shape changes with time, but after 5–7 scans stable curve is obtained. In all conditions the anodic to cathodic charge ratio is larger than unity. The peak current is proportional to the concentration of the redox probe in organic phase and salt in aqueous phase, whereas the midpeak potential is almost not affected by these factors. It has been concluded, that the electrooxidation of redox probe within hydrophobic silicate matrix is followed by two simultaneous processes: t‐butyloferrocenium cation transfer to the aqueous phase and anion transfer from aqueous phase. Their relative contribution depends on the ratio of concentration of the redox probe in organic phase to concentration of salt in aqueous phase.
What factors influence failure to engage in a supervised self‐help programme for bulimia nervosa and binge eating disorder?
Authors: Bell Lorraine , Newns Kathryn 
Published: March 2004

AbstractThe study investigated factors influencing failure to engage among a group of bulimic and binge eating disordered clients referred to a supervised self‐help programme. A total of 125 patients referred to a supervised self‐help programme for people with bulimia and binge eating disorder were grouped into those who were seen in treatment (n = 85), and those who failed to engage i.e. did not attend their initial appointment (n = 40). Diagnosis, age, gender and waiting times of the two groups were compared. Diagnosis, age and gender were not significantly different between the two groups. The only significant factor measured was the length of time that they had waited between being referred to the service and their appointment date. Clients who waited less than 4 weeks were 2.4 times more likely to attend their appointment. For every week that lapsed between referral and appointment date, the odds of attending were reduced by 15% (p = 0.002). The results are discussed in light of the importance of maximizing engagement in treatment. Copyright © 2004 John Wiley & Sons, Ltd and Eating Disorders Association.
Processing of five types of ‘threat’ information in anorexic and bulimic women
Authors: Quinton Stephanie 
Published: March 2004

AbstractThis study investigated further the ‘escape’ hypothesis of bulimia and compared the processing of ‘threat’ information in control, anorexic and bulimic women. Using a novel information‐processing task, five types of non‐eating ‘threat’ (autonomy, sociotropy, discomfort anxiety, ego threat from others and ego threat from self) were addressed. The women did not differ in response time taken to identify ‘threat’ information, although there was support for the ‘escape’ hypothesis of bulimia. Specific non‐eating ‘threat’ information appeared relevant to both anorexia and bulimia nervosa, suggesting the potential value of addressing general threat schemata in clinical practice. Copyright © 2004 John Wiley & Sons, Ltd and Eating Disorders Association.