bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved performance of carbon paste amperometric biosensors through the incorporation of fumed silica
Authors: Wang Joseph , Naser Najih 
Published: May 2005

AbstractThe sensitivity and stability of carbon paste enzyme elearodes are greatly enhanced through the incorporation of fumed silica within the paste matrix. The improved performance is attributed to the adsorptive and electrocatalytic properties of the silica nanoparticles. The electrocatalytic action results in a substantial lowering of the overvoltage for both the oxidation and reduction of the enzymatically liberated peroxide species. Highly selective, low‐potential, biosensing of glucose is thus accomplished in the presence of coexisting acetaminophen, ascorbic acid, or uric acid. The enhanced performance accrued from the presence of silica is also illustrated for mediator (dimethyl ferrocene)‐containing pastes. High enzymatic activity is maintained over prolonged periods. The silica modification strategy provides an effective, fast, and inexpensive route for immobilizing enzymes within carbon paste matrices.
Direct determination of indole‐3‐acetic acid in plant tissues by electroanalytical techniques using a carbon paste modified with OV‐17 electrode
Authors: Hernández P. , Galán F. , Nieto O. , Hernández L. 
Published: May 2005

AbstractThe electrochemical behavior of indole‐3‐acetic acid (IAA) with a silicone OV‐17 modified carbon paste electrode was explored for the determination of this compound in plant tssues. Under optimum conditions, the procedure gave a linear concentration range up to 0.6 μg mL−1 detection of 0.053 μ mL−1 containing the preconcentration solution 0.08M Hac/Ac− buffer (pH4) and 0.4 M phosphate buffer (pH12) as a supporting electrolyte in the measurement cell. The accumulation time was 10 minutes and the sweep potentials were carried mV s−1 with a pulse amplitude (ΔE) of 100 mV. This method is available for the determination of IAA in plant tissues.
Simultaneous voltammetric determination of hypoxanthine, xanthine, and uric acid
Authors: Goyal R. N. , Mittal Alok , Sharma Sonam 
Published: May 2005

AbstractA rapid voltammetric method for the simultaneous determination of hypoxanthine, xanthine, and uric acid has been developed at pyrolytic graphite electrode (PGE). The limit of detection is 10 μM and the response is linear up to 0.5 mM. The relative standard deviation was 0.57, 0.59, and 0.62% for hypoxanthine, xanthine, and uric acid, respectively.
Screen‐printed voltammetric and amperometric electrochemical sensors for decentralized testing
Authors: Hart John P. , Wring Stephen A. 
Published: May 2005

AbstractThis review describes the design and fabrication of screen‐printed voltommetric and amperometric electrochemical sensors, together with their applications for decentralized monitoring of several naturally occurring biomolecules, drugs, and potential environmental and industrial pollutants or toxins.
Toluidine blue covalently immobilized onto gold electrode surfaces: An electrocatalytic system for nadh oxidation
Authors: Schlereth Daniela D. , Katz Eugenii , Schmidt Hanns‐Ludwig 
Published: May 2005

AbstractThe electrochemical behavior of toluidine blue in solution has been studied and found to be strongly dependent on the electrode surface nature. Monolayers of cystamine (C) or 3‐mercaptopropionic acid (MP) chemisorbed onto gold electrode surfaces have been used as support for covalent attachment of toluidine blue (TOB) through its aromatic amino group in position 3 and the amino or carboxylic groups covering the elearode surface. After covalent attachment of TOB onto an MP monolayer, three different species remained stably attached to the electrode surface. Physically adsorbed TOB, which showed the same midpoint potential as in the solubilized state, E1/2 = –245 mV (Ag/AgCl); covalently attached TOB, whose midpoint potential was shifted toward 120 mV more positive potentials; and an unknown species, probably physically adsorbed TOB dimers, with a midpoint potential, E1/2 = +135 mV (Ag/AgCl).Toluidine blue modified electrodes started to oxidize catalytically NADH at –100 mV with an amperometric response dependent on the concentration of the substrate. An electrode fouling process was observed after successive additions of NADH leading to the loss of catalytic activity.
Voltammetry of adenosine after electrochemical treatment of carbon‐fiber electrodes
Authors: Chen Ta K. , Strein Timothy G. , Abe Takayuki , Ewing Andrew G. 
Published: May 2005

AbstractVoltammetry of adenosine after electrochemical treatment is explored. The activations scheme includes an anodic potential (+2.2 V) for 125 ms and a cathodic potential (–1.0 V) for 75 ms. Subsequent staircase voltammetry can be used to obtain both qualitative and quantitative information. This activation procedure has been applied to 11 μm carbon‐fiber microelectrodes to obtain reproducible voltammograms for adenosine. To characterize this activation procedure, the effect of the magnitude and duration of both the anodic and the cathodic potentials have been studied. Data obtained suggest that the magnitude of the applied potential pulse is critical to proper electrode activation, whereas duration and total charge passed have minimal effects.
Determination of hydrophobic substances in aqueous‐organic and micellar media by use of electrochemical techniques
Authors: Paredes María I. , González Maríia C , Vázquez Maríia D. , Tascón Maríia L. , Batanero Pedro Sánchez , Patriarche Gaston J. 
Published: May 2005

AbstractA new electroanalytical methodology for the determination of hormones in micellar media by use of differential pulse polarography (DPP) and adsorptive stripping voltammetry (ASV) is reported. It was applied to the determination of hydroxyprogesterone in Triton X‐100 as micellar medium, with a detection limit of 3.6 × 10−6 M (DPP) and 2.5 × 10−11 M (ASV). A theoretcal explanation for the increased diffusion current of the hormone in the micellar medium is provided and its significance discussed. The electrochemical behavior of this hormone and β‐estradiol in aqueous‐organic media was also studied by using DPP and ASV. The detection limits thus obtained for the two compounds were 1.2 × 10−5 M β‐estradiol and 1.5 × 10−5 M hydroxyprogesterone by the former technique and 8 × 10−9 M hydroxyprogesterone by the latter. The β‐estradiol showed no adsorption in any of the assayed media, so the ASV determination of hydroxyprogesterone in its presence was highly selective.
Trace analysis at a mercaptoacetic acid‐modified electrode
Authors: Zhou Yanxiu , Zhu Guoyi , Wang Erkang 
Published: May 2005

AbstractThe strong chelating ability of mercaptoacetic acid for certain metal ions is exploited for a new kind of voltammetric sensor. Specifically, a glassy carbon electrode (GCE) surface was covalently covered by mercaptoacetic acid. The preparation of mercaptoacetic acid‐modified glassy carbon electrode (MMGCE) under various conditions is explored. The electrodes so formed were able to chemically collect metal ions such as mercuric ions and yielded a 10‐fold greater voltammetric response than a bare glassy carbon surface. The response was characterized with respect to pH, preconcentration time, mercury(II) concentration, and other variables. For 3 minute preconcentration, the electrode gives good linearity for 1 × 10−8 mol/L to 1 × 10−9 mol/L mercuiy(II). The response can be reproduced with a 7.7% relative standard deviation. A range of analytical methods, including electrochemical, electron spectroscopy for chemical analvsis (ESCA) techniques, and alternating current (AC) polarography has been used to characterize these novel modified dectrpdes. The reaction of MMGCE to mercury ion is produced by weak adsorption.
Humic acids interactions with metal salts incorporated into the carbon paste electrode
Authors: Kula Petr , Navrátilová Zuzana 
Published: May 2005

AbstractThe carbon paste electrode (CPE) modified with metal salts [CuCO3. Cu(OH)2 and Ag2SO4] was developed. The voltammetric measurement on these modified electrodes in the presence of humic ligands indicated metal complexation reactions. These electrodes offer the possibility of using them in the study of metal‐humic substances interaaions and in the study of minerals behavior in the solutions of humic acids (HAs).
Quantitative analysis of zopiclone in tablets using ion‐selective electrode and polarographic methods
Authors: Bouklouze A. A. , Viré J.‐C. , Quarin G. C. , Kauffmann J.‐M. 
Published: May 2005

AbstractDifferent types of PVC‐matrix ion‐selective electrodes (ISEs) that respond to the cationic form of zopiclone are described. Four ion‐pairing agents, namely tetraphenylborate (TPB), reineckate (RN), phosphotungstate (PT) and silicotungstate (ST), and different plasticizers are investigated. The best PVC polymeric membrane contains nitrophenyloctylether (NPOE) as plasticizer and zopiclone‐TPB as active material. This electrode exhibits a Nernstian response (60 mV per decade) in the range 1 × 10−2 to 1 × 10−5 M and a fast dynamic response time, this response being not affected by pH between 1.9 and 5.5. Direct potentiometry was used to determine zopiclone in drug formulations using this new zopiclone‐selective electode. The results are comparable to those obtained by differential pulse (DP) and square‐wave (SW) polarographic techniques using both direct and standard addition methods.
Carbon paste electrode and medium‐exchange procedure in adsorptive cathodic stripping voltammetry of selenium(IV)
Authors: Ferri Tommaso , Guidi Francesco , Morabito Roberto 
Published: May 2005

AbstractAn adsorptive cathodic stripping voltammetric method for the determination of Se(IV) is described. The method is based on the detection of the piazselenol complex formed by Se(IV) with 2,3‐diamino naphthalene (2,3 DAN) at pH 2 (0.01 mol L−1 HC1 + 0.1 mol L−1 KC1). The method is based on a medium‐exchange scheme and a carbon paste electrode (CPE). The preconcentration step is carried out at open circuit, and then the complex is stripped out by linear sweep voltammetry (LSV) after medium exchange (0.1 mol L−1 HNO2 + 0.1 mol L−1 KNO3 where the working electrode is transferred). The method is characterized by a precision better than 8% and a limit of quantitation (10 times the standard deviation of the blank) of 1.25 × 10−7 mol L−1 (for 20 minutes of preconcentration time). The use of CPE coupled with the medium‐exchange scheme reduces the interferences (especially by different classes of surfactants) and improves the selectivity (much better than in the usual cathodic stripping voltammetry on mercury).
Adsorptive stripping tensammetry of oxyethylene‐oxypropylene block copolymers
Authors: Szymanski Andrzej , Lukaszewski Zenon 
Published: May 2005

AbstractThe behavior of oxyethylene‐oxypropylene block copolymers (OEOPBC) of EPE type was investigated. Most of the investigations were performed with OEOPBC having 30 oxypropylene subunits and different lengths of oxyethylene chain. The dependences of the peak height on the concentration of surfactant, preconcentration time, and preconcentration potential were examined. OEOPBC partially behave in agreement with the general scheme of the behavior of ethoxylates, formulated on the basis of previous studies and predicting two types of behavior. The scheme has been supplemented with the third type of behavior on the basis of this work: a single peak is formed whose potential is stable, independent of changes of the surfactant concentration, preconcentration time, and potential. All the investigated OEOPBC give peaks suitable for analytical purposes.
On the electrochemical study of an enzymatic model reaction
Authors: Pineda Teresa , Blazquez Manuel 
Published: May 2005

AbstractThe reaction between pyridoxal (PL) and L‐alanine (Ala) was studied as a function of the pH and the amino acid to aldehyde initial concentration ratio. The electroreduction of the Schiff base formed and the free PL in solution was observed by classical (CP) differential pulse polarography and linear scan cyclic voltammetry (LSCV). From the evolution of the waves under different experimental conditions, the apparent formation constant of the Schiff base was determined. From polarographic and kinetic parameters, the electroreduction process in different pH zones was described. Voltammetry was used to determine the formation constant of the unprotonated Schiff base from unprotonated species of aldehyde and amino acid. Acid‐base constants of the Schiff base were determined from UV‐visible spectra. These results are compared with other Schiff bases related to PLP‐dependent enzymes.
Characterization of CE and CEC processes under pure kinetic conditions by linear‐sweep voltammetry
Authors: Mellado J. M. Rodríguez , Montoya M. Ruiz 
Published: May 2005

AbstractTheoretical equations applying to voltammetric curves corresponding to electrochemical processes preceded by a chemical reaction under pure kinetic conditions are derived. Logarithmic analyses for CrEr, CrEi, and CrErCi, processes are proposed. The equations are tested with the aid of well‐known reduction processes.
Cathodic stripping voltammetry of the copper–1,10‐phenanthroline complex
Authors: Čuljak I. , Mlakar M. , Branica M. 
Published: May 2005

AbstractCathodic stripping voltammetry of copper, based on the accumulation and reduction of its complex with 1,10‐phenanthroline (phen), has been studied. The complex is reduced in two steps from CuI–phen and CuII–phen to copper amalgam at potentials of −0.43 and −0.62 V vs. Ag/AgCl, respectively. The reduction processes are strongly dependent on the pH of the solution, as well as on the concentration of the metal ion and ligand. The reduction mechanism of both complexes was established. The detection limit for copper in 0.55 mol/LNaCl with 20 min accumulation at 0.0 V vs. Ag/AgCl, measuring the reduction peak of the CuI–phen complex at −0.43 V vs. Ag/AgCl by SWV, was found to be about 5 × 10−10 mol/L. The reaction parameters were calculated by square‐wave voltammetry (SWV), i.e., transfer coefficients α = 0.31 and α = 0.45, and the maximum surface concentrations Γ = (2.02 ± 0.08) × 10−11 mol/cm2 and Γ = (2.83 ± 0.12) × 10−12 mol/cm2. Measurements of the copper content in natural seawater samples were performed as well.
Comparative study of polymer‐coated mercury film electrodes for voltammetric analysis of lead and cadmium in the presence of surfactants
Authors: Dam M. E. R. , Thomsen K. N. , Pickup P. G. , Schrøder K. H. 
Published: May 2005

AbstractFour different polymer‐modified mercury film electrodes (MFEs) on a glassy carbon substrate were tested for their ability to determine lead and cadmium in the presence of surfactants. The polymers used for electrode modification were: Nafion, polyaniline, base‐hydrolyzed cellulose acetate, and base‐hydrolyzed poly(ethyl 3‐thiophene acetate). Triton X‐100, sodium dodecyl sulfate, dodecyl pyridinium chloride, and bovine serum albumin were chosen as representatives of surface active compounds. It is shown that polymer‐covered electrodes are useful in surfactant‐containing media in some instances, but none of them remained unaffected by any of the four surfactants. The cellulose acetate electrodes seem to be less affected by proteins than the bare MFE and other modified electrodes. The Nafion and cellulose acetate‐coated electrodes were used for the determination of lead in filtered and acidified, but otherwise untreated, water samples from a sewage treatment plant. The results obtained with the cellulose acetate‐coated electrode were in good agreement with those from atomic absorption spectroscopy.
Adsorptive stripping tensammetry of oxyethylated isooctylphenols of the triton X series
Authors: Szymanski A. , Lukaszewski Z. 
Published: May 2005

AbstractThe dependence of the peak height on the concentration of surfactant, the preconcentration time, and the preconcentration potential was examined. The behavior of the Triton X series fits the general scheme of the behavior of ethoxylates. Tritons having a lower number of ethoxylene subunits (EO) (1–12.5) form wide, analytically useful peaks within the range of the growing section on the calibration plot. A further increase in the concentration causes complicated transformations to appear on the tensammetric curve, which are caused by association. The wide peak is shifted irregularly in the negative direction and finally disappears, being transformed into a vertical line. An additional, usually needle‐shaped peak appears instead. Surfactants having a higher EO (30–40) form a narrow double peak, which is an analytically useful signal; this transforms into a single narrow one when the concentration increases. The higher the EO in Tritons, the broader the range of potentials for their adsorption.
Simultaneous assays of glucose, urate, and cholesterol in blood serum by amperometric flow injection analysis
Authors: Yao T. , Satomura M. , Nakahara T. 
Published: May 2005

AbstractGlucose, uric acid, and cholesterol in serum were assayed simultaneously in a flow injection system by using a 16‐way switching valve and a parallel configuration of three immobilized enzyme reactors. Nafion film‐coated and Nafion/cellulose acetate film‐coated platinum electrodes were used to selectively detect the hydrogen peroxide generated enzymatically in the enzyme reactors, without any interferences from electroactive species such as L‐ascorbate and proteins present in the serum. The signal current was linearly related to the glucose concentration in the range of 5–700 mg/dL, to the urate concentration in the range of 1–80 mg/dL, and to the cholesterol concentration in the range of 5–100 mg/dL. The precision (coefficient of variation) was better than 2.8% for the simultaneous assay of the three species in human control serum. The assay speed was up to 32 samples per hour.
Cleaning up procedure for Captopril determination in urine samples by a nonintrusive method
Authors: Passamonti P. , Pucciarelli F. 
Published: May 2005

AbstractThis communication suggests how the S/N ratio in the electrochemical determination of Captopril in urine samples can be simply improved. The proposed method involves unselective degradation of the proteins present in urine samples by refrigerating them down to −196°C. The separation is accomplished via ultracentrifugation at room temperature in such a way that very little manipulation of the sample occurs. This physical method is a useful tool for reducing background noise due to adsorbable products and for handling the sample as little as possible.
Thermal and photochemical control of an electrochemical process at an isomerizable spiropyran monolayer‐modified Au electrode
Authors: Katz Eugenii , Willner Itamar 
Published: May 2005

AbstractAn isomerizable monolayer‐modified electrode is used to control interfacial electron transfer by means of external signals. A spiropyran (SP) monolayer undergoes thermal isomerization to the positively charged merocyanine monolayer, MRH+, while the latter isomer monolayer is photoisomerized, λ > 475 nm, to the SP‐monolayer state. Pyrroloquinolino quinone (PQQ) is used as redox component for probing the interfacial electron transfer. The MRH+‐monolayer electrode attracts the negatively charged PQQ and effective electron transfer is attained. Upon photochemical isomerization to the SP‐monolayer electrode, the interfacial electron transfer is inhibited. Reversible activation and deactivation of the interfacial electron transfer is accomplished by cyclic isomerization of the monolayer through the MRH+ and SP‐states, respectively, using thermal and photochemical signals.
Study of the nickel‐based chemically modified electrode obtained by electrochemical deposition of an NiII‐tetramethyl‐dibenzo‐tetraaza [14] annulene complex. Redox catalysis of carbohydrates in alkaline solutions. II
Authors: Cataldi Tommaso R. I. , Desimoni Elio , Ricciardi Giampaolo , Lelj Francesco 
Published: May 2005

AbstractThe electrochemical treatment of an electropolymerized (NiIIL)n thin film (where L represents 5,7,12,14‐tetramethyl‐dibenzo[b,i]‐1,4,8,11‐tetraaza [14] annulene) gives rise to a nickel‐based catalytic deposit on conducting substrates [glassy carbon (GC), platinum, or gold electrodes], which shows strong similarities to the nickel hydroxide electrode. The effect of potential cycling on surface composition, chemical status, and morphology of this nickel‐based chemically modified electrode (Ni‐CME) has been investigated by cyclic voltammetry (CV) [1], X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy. XPS analysis was very useful for characterizing the chemical changes in the nickel coordination caused by electrochemical treatments in alkaline solution. The featureless surface of the as‐prepared GC/(NiII)Ln, film compared with the fractal nature of the GC/Ni‐CME was revealed by electron micrographs. The Ni‐ CME exhibits high electrocatalytic activity towards the oxidation of carbohydrates in alkaline solution. The electrooxidation capability of the Ni‐CME is highlighted by the amperometric detection of sugars after anion‐exchange liquid chromatographic separations with alkaline mobile phases.
Lipid‐modified pyrolytic graphite electrodes for the study of negatively charged species
Authors: Bianco Pierre , Haladjian Jean 
Published: May 2005

AbstractPyrolytic graphite (PG) electrodes are coated with films of dodecylamine (DDA), dimethyldioctadecylammonium bromide (DODAB) or composite layers based on a mixture of phosphatidylcholine (PC) and cholesterol (CH). Cyclic voltammetry is used to investigate the incorporation of two negatively charged species, Fe(CN) and spinach ferredoxin, into the DDA or DODAB layers, as a function of time and composition of the cast films. No signal corresponding to the spinach ferredoxin redox reaction is detected at the PG electrode simply coated with a mixed (PC‐CH) layer. Well‐shaped responses denoting redox reaction of ferredoxin are observed when the (PC‐CH) layer is doped with DDA (or DODAB). The results support the electrostatic nature of the interactions between negatively charged species and the positive charges in the lipid layer.Such coated electrodes seem well‐suited for studying negatively charged species. They provide a good model for mimicking physiological redox protein‐membrane interactions.
Adsorptive stripping voltammetric determination of ultratrace concentrations of molybdenum in biological and environmental materials on a glassy carbon mercury film electrode
Authors: Adeloju Samuel B. O. , Pablo Fleurdelis 
Published: May 2005

AbstractThe determination of ultratrace concentrations of molybdenum(VI) by adsorptive cathodic stripping voltammetry on a glassy carbon mercury film electrode is described. The method involves a controlled preconcentration of the element by interfacial accumulation as molybdenum‐8‐hydroxyquinoline (oxine) complex on the electrode followed by a cathodic stripping voltammetric measurement. The optimum analytical conditions for the measurement of molybdenum by this method include the use of 0.20 M acetate buffer at pH 5.25, 1 mM oxine, an accumulation potential of −0.40V (vs. Ag/AgCl) and a rotated electrode at 3000 rpm. Under these conditions, the linear concentration range and lowest detectable concentration obtained with a 5‐min accumulation were 0–300 μg L−1 (R2 = 0.997) and 0.5 μg L−1 [relative standard deviation (RSD) = 13.7%], respectively. The presence of most other metal ions do not interfere with the molybdenum determination, except for PbII and CdII which were successfully masked by addition of 3 μM EDTA, and TiIV and WVI which were masked by 1 μM tartaric acid. The interference of surface‐active substances, such as Triton X‐100, is overcome by UV irradiation of the sample. The use of the adsorptive stripping voltammetric technique, after decomposition by dry ashing and UV treatment, is successfully demonstrated for the determination of molybdenum in biological and environmental materials.