bluuebunny/crossref_metadata_2025_split huggingface dataset:
Insecticide determination with enzyme electrodes using different enzyme immobilization techniques
Authors: Kumaran Satish , Tran‐Minh C. 
Published: May 2005

AbstractThree different techniques of immobilization of the enzyme butyrylcholinesterase (E.C. 3.1.1.8.) and their use in association with pH glass electrodes for the determination of certain insecticides (Carbofuran, Carbaryl, and Paraoxon) by inhibition of the enzyme, have been studied and the results obtained are compared. The immobilizations are done by cross‐linking a mixture of the enzyme and human serum albumin with glutaraldehyde onto nylon nets, by fixing the enzyme onto commercially available polyamide pre‐activated PALL™ membranes and by physically retaining the enzyme in a synthetic prepolymer of acrylamidemethacrylamide hydrazides which is cross‐linked with glyoxal. There are no significant differences with regard to the sensitivities or the detection limits among the sensors using the different membranes. The detection limits of the insecticides tested varied from 0.2 to 10 ppm. In terms of signal reproducibility, stability, and cost, the nylon net membranes appear most promising. Membranes prepared in lots show better sensor signal reproducibility compared to those prepared individually. For the development of “disposable” biosensors, both nylon net and PALL™ membranes are very apt, since these membranes are easily mass produced at low cost and maintain their original enzyme activities even after 3 years when stored dry.
Electrochemical analysis of arsenic compounds for veterinary use by two polarographic methods
Authors: Tzedakis T. , Comtat M. 
Published: May 2005

AbstractSome compounds with the general formula magnified image (I) have an antiparasitic effect on animals and are used against heart disease induced by trypanosomes. A rapid, precise and selective analysis of species (I) and RNHC6H4AsO3H2 (II), RNHC6H4As  O (III), and R'SH (IV), appearing as intermediates, is necessary in order to regulate the synthesis processes if (I) and (II), to identify and measure the products before using them in the reactor, and to control their purity before scaling up. Tast polarography and differential pulse polarography convert quickly the concentration of these compounds into current intensity suitable for control of the process. The first method makes the assay in oxidation of (IV) possible, but the resolution is insufficient to obtain the species (III) and (I). The assay, in reduction of (II) is possible, but with interferences of (III). The second method, on the other hand, using oxidation of (I) in a basic medium provides sufficient resolution to analyze (I) and (III) with a precision on the order of 5%.
Logarithmic analysis of polarographic waves complicated by nonparallel initial and limiting currents
Authors: Lovrić Milivoj , Svetličić Vesna , Žutić Vera 
Published: May 2005

AbstractA procedure for the logarithmic analysis of polarographic waves with nonparallel initial and limiting currents is developed and its application illustrated with two experimental systems: phosphine‐metriphonate reduction and methylene blue (MB) reduction and reoxidation. The procedure is based on the presumed identity of the wave function and the change of a double‐layer capacitance along the wave.
An X‐ray photoelectron spectroscopy investigation of silver iodide‐coated ion‐selective electrodes
Authors: Strydom C. A. , van Staden J. F. , Strydom H. J. 
Published: May 2005

AbstractThe AgI‐coated ion‐selective electrode surface is more stable than either the AgCl or AgBr surfaces if exposed to solutions containing ions such as Cl−, Br−, I−, Ag+, and NH3 for a week. A mixed AgClsI1− or AgBrsI1−s phase is formed upon a week's treatment of the AgI surface with either Cl− or Br−, with S much smaller than 1. After a week's treatment with high concentrations of the ions, no new surface layer consisting of only AgCl or AgBr is formed, as was observed in the case of AgCl and AgBr electrodes. Although AgI is much less soluble than either AgCl or AgBr, the absorption of chloride and bromide ions into the AgI surface nevertheless increases with time.
Cobalt(II, III)‐oxide chemically modified electrode as amperometric detector in flow injection systems
Authors: Mannino S. , Cosio M. S. , Ratti S. 
Published: May 2005

AbstractA chemically modified electrode (CME) prepared by mixing cobalt(II, III) oxide and carbon paste, greatly reduces the overvoltage for the oxidation of various biologically important compounds, such as sugars, hydrogen peroxide, and cysteine. The new electrocatalytic surface facilitates the amperometric detection of these compounds in flowing streams. The modified electrode is very stable, can be easily renewed, and gives reproducible results. Application for the determination of hydrogen peroxide in milk is demonstrated.
An improved holder for the electrochemical quartz crystal microbalance and its cyclic voltammetry characteristics
Authors: Koh Wonyong , Kutner Wlodzimierz , Jones M. Thomas , Kadish Karl M. 
Published: May 2005

AbstractThe design and characteristics of a stationary, compact holder for an electrochemical quartz crystal microbalance (EQCM) are presented. A Au/quartz crystal oscillator is vertically mounted in a polytetrafluoroethylene body of the holder. The crystal is sealed with an O‐ring and is easily accessible for change. The performance of the holder was tested under cyclic voltammetry (CV) conditions with the Ag+ /Ag and Cu+ /Cu electrodeposition/electrodissolution processes. Frequency changes due to mass changes of the Au/quartz electrode were correlated with CV parameters. The holder was calibrated for a 5 MHz crystal oscillator by means of CV anodic stripping of silver. The mass sensitivity was 19.5 ± 0.1 ng Hz−1 cm−2. The concentration sensitivity was 14.2 ± 0.2 μM Hz−1 cm−2 at a potential scan rate of 0.01 V s−1 and 23.7 ± 0.3 μM Hz−1 cm−2 at a scan rate of 0.02 V s−1 for a potential of scan reversal which was 250 mV more negative than the electrodeposition peak potential.
Determination of copper(I) ion with a chemically modified carbon paste electrode based on di(2‐imino‐cyclopentylidine mercaptomethyl) disulfide
Authors: Won Mi‐Sook , Park Jin‐hyo , Shim Yoon‐Bo 
Published: May 2005

AbstractA copper‐sensitive chemically modified electrode (CME) has been constructed by incorporating di(2‐imino‐cyclopentylidine mercaptomethyl) disulfide (didd) into the carbon paste composed of graphite powder and Nujol oil. Copper(I) ion was chemically deposited on the CME by immersing it in the Cu(I) solution. The resulting surfaces were characterized by cyclic and differential pulse voltammetry. The CME's surface could be regenerated by applying more positive potential than the stripping potential of the Cu(I) ion and then used for another deposition. After seven deposition/measurement/ regeneration cycles, the peak current of voltammograms of the analyte decreases slightly. The differential pulse technique was also applied to the above system. In this case, the detection limit for Cu(I) ion was 5 × 10−11 M for 30 minutes of deposition time. After reduction of Cu(II) ion to Cu(I) in the sample solution with hydroxylamine, satisfactory results were obtained for the determination of copper in certified standard urine reference material SRM's 2670 (trace elements in urine).
New electroanalytical method for determination of chloride ion at low concentrations
Authors: Sun Tianlin , Bai L. , Conway B. E. 
Published: May 2005

AbstractA sensitive electroanalytical procedure is described for the detection of chloride ion down to micromolar concentration and over a wide linear range of (3.5) decades. The method is based on the blockage of a Pt anode caused by competitive adsorption of chloride ion, using cyclic voltammetry. The blocking effect is proportional to p[Cl−] over a wide concentration range; the significance of this relationship is discussed. The required conditions for this electroanalytical procedure are described and interferences from other anions are evaluated.The new method is sensitive, accurate, and simple, and it is useful for analyzing trace chloride ion in nominally pure inorganic chemicals.
Voltammetric characterization of activated carbons in modified carbon paste electrodes
Authors: Kaplan Jeffrey D. , Marsh John H. , Orchard S. Walter 
Published: May 2005

AbstractCarbon paste electrodes (CPEs), modified by the addition of small amounts of finely powdered activated carbon (AC) were studied using cyclic (CV) and square wave voltammetry (SWV). Cyclic voltammograms revealed the expected increase in surface area associated with the presence of the activated carbon but did not reveal any specific redox peaks. Square wave voltammograms of both the modified and unmodified electrodes obtained in acidic solution were characterized by well‐defined redox peaks whose behavior was consistent with that expected for couples of the quinone/hydroquinone type. The modified electrodes showed generally larger peaks than the unmodified ones. Regardless of the origin of the activated carbons, the square wave voltammetric response was fairly similar, and it was not possible to confidently differentiate between the different types on this basis.
Performance characteristics of a Labetalol‐H plus‐tetraphenylborate selective electrode
Authors: Voulgaropoulos Anastasios , Sofoniou Michalis , Kazakou Eleni 
Published: May 2005

AbstractThe construction and performance characteristics of an ion selective membrane electrode for labetalol drugs in protonated form, based on their ion‐pair complexes with sodium tetraphenylborate (TPB‐Na+) incorporated in a poly(vinyl chloride) matrix, are described. The Labetalol‐H+ selective electrode can be used practically for the determination of the pharmaceutical compound by direct potentiometry. The potentiometric sensor exhibits near‐Nernstian response from 10−2 M to about 10−5 M, with a slope of 55 mV/decade of concentration and detection limit of 4.46 × 10−6 M. The influence of changing the membrane characteristics, pH, and temperature of the test solution on the electrode potential are studied. The response time varies from a few seconds to several minutes, depending on labetalol concentration. The selectivity of the electrode for Lab‐H+ toward primary, secondary, tertiary, and quaternary amines is investigated. Determination of Lab‐H+ in pharmaceutical tablets is performed using the proposed membrane electrode. No interference from any excipients in the tablets was observed.
Application of adsorptive stripping voltammetry to trace measurements of molybdenum in plant materials
Authors: Karakaplan Mustafa , Henze GÜNter 
Published: May 2005

AbstractA procedure is presented for quantifying molybdenum in dry ashed plant samples. The determination is made by adsorptive stripping voltammetry in the differential pulse mode (DPAdSV). It is based on the adsorptive accumulation of the Mo(VI)‐chloranilic acid complex on the surface of a hanging mercury drop, followed by the reduction of the adsorbed complex. Optimal conditions are stirred acidified supporting electrolyte solution (of pH 2–3), containing 10−3 mol/L chloranilic acid and an accumulation potential of −0.20 V (vs. Ag/AgCl, 3 mol/L KCl). The height of the cathodic stripping peak around −0.60 V depends linearly on the molybdenum concentration and accumulation time (over the ranges 0–12 ng/ml and 0–300 seconds, respectively). For an accumulation period of 5 minutes, the detection limit is 0.02 ng/ml. Possible interferences by other trace metals are investigated. The proposed procedure has been applied to the determination of molybdenum traces in a variety of plants with good accuracy and precision. The results are in good agreement with those obtained by atomic absorption spectrometry.
Amperometric detection after HPLC separation of selected polypeptides and proteins at an electrode modified by mixed valent ruthenium oxide crosslinked with cyanide
Authors: Przyjazny Andrzej , Cox James A. 
Published: May 2005

AbstractAn indicator electrode, in which a film containing Ru oxides with cyano‐crosslinks comprised the active surface, was used in an amperometric detector for ion‐exchange and reverse‐phase high‐performance liquid chromatography (HPLC). The latter used a C‐18 column and an eluent of 0.04 M citric acid, 0.1 M KH2PO4, 0.1% trifluoroacetic acid, and 20–80% acetonitrile. Oxytocin, isotocin, vasopressin, tocinoic acid, myoglobin, and ribonuclease A were separated and determined with detection limits at the 1–3 pmol level. The response to ribonuclease A, as a typical example, was linear over the range of 0.050‐2.5 μM, with a slope of 15 nA/μM at 0.94 V (vs. Ag/AgCl). A single preparation of the electrode was generally stable for 3 weeks, as long as the analyte concentrations were below 10 μM.
Polarography and stripping voltammetry of metal‐polycarboxylate complexes: The Cu(II)‐polyacrylate system
Authors: Díaz‐Cruz J. M. , Ariño C. , Esteban M. , Casassas E. 
Published: May 2005

AbstractA systematic study of the voltammetric behavior of Cu(II) in the presence of polyacrylic acid (PAA) was carried out by means of sampled direct current polarography (DCP), normal pulse polarography (NPP), differential pulse polarography (DPP), reverse pulse polarography (RPP), cyclic voltammetry (CV), and differential pulse anodic stripping voltammetry (DPASV). Background currents due to PAA, and probably anodic oxidation of the Hg in this potential region, hinder the study of the Cu(II) reduction. Results obtained seem to indicate the lability of the Cu/PAA complex. Distorted DPASV signals are obtained for Cu(II) in the presence of PAA, which are explained on the basis of the change of the ligand‐to‐metal ratio during the different steps of the electrodic process. Titrations of Cu(II) with partially neutralized PAA allow the determination of the apparent formation constant K of the Cu/PAA complex system.
Electrooxidation of ascorbic acid at the bis(4‐pyridyl)disulfide modified gold electrode
Authors: Xie Yuanwu , Dong Shaojun 
Published: May 2005

AbstractThe electrooxidation of ascorbic acid (AA) at the bis(4‐pyridyl)disulfide (PySSPy) modified gold electrode was studied. The results showed that the oxidation process was pH‐dependent. It was mainly due to the static interaction between AA and the modified electrode surface. At pH < 5.5, the oxidation is controlled by diffusion and the electrode can be applied to the kinetic and mechanistic study. In the range of 5 × 10−6– 2 × 10−3 mole/L, the peak currents exhibit a good linear relationship with the concentration of AA. The modified electrode has greater stability and can be used in flow detection analysis.
Determination of arsenic by stripping potentiometry on gold electrodes using partial least‐squares (PLS) regression calibration
Authors: Jagner Daniel , Renman Lars , Stefansqottir Svana H. 
Published: May 2005

AbstractPartial least‐squares (PLS) regression calibration was applied to the determination of arsenic by stripping potentiometry on gold electrodes. In a procedure involving the direct electrochemical reduction of arsenic (V), this allowed interferences from copper (II), due to formation of intermetallic compounds, and tin (IV), due to stripping peak overlaps, to be modeled. At levels of arsenic below 1 μg L−1, additional problems with the gold surface background, as well as copper interferences from a reagent blank, could be successfully modeled, and the prediction of sample concentrations could be accurately performed.
Studies on the electrocatalytic reduction of aliphatic aldehydes on palladium‐modified carbon paste electrodes
Authors: Cai Xiaohua , Kalcher Kurt 
Published: May 2005

AbstractCarbon paste electrodes modified either by mixing palladium powder to the electrode material or by electrodepositing Pd via cycling the potential between 0.4 and −0.7 V (versus SCE) exhibited stable electrocatalytic response for aliphatic aldehydes and aliphatic alcohols. The aldehydes (e.g., formaldehyde) could be reduced to the corresponding alcohols (e.g., methanol), and the alcohols (e.g., methanol) could be oxidized to the corresponding aldehydes (e.g., formaldehyde) by direct current voltammetry (DCV). The electrocatalytic effect was attributed to the electrogenerated metallic palladium at the electrode surface. The cathodic current peak, the height of which was proportional to the aldehyde concentration, had negative values; it was ascribed to a desorption of the product of the electrode reaction from the surface of the electrode. This peak was used for quantitative analytical purposes.
A study of electrical double layer effects in the pretreatment of two‐electrode cells for enzyme electrodes
Authors: Higson Séamus P. J. , Vadgama Pankaj 
Published: May 2005

AbstractThe thermodynamics of the electrode/electrolyte interface have been described for a two‐electrode cell, using a classical Guhemian approach. The description has been related to a two‐electrode cell that frequently is employed for enzyme electrodes. Theoretical considerations of the electrical double layer have been correlated with conditioning pretreatment regimes for the preparation of enzyme electrode cells. Effects of electrolyte composition and effects of concentration have been described. Consequently, improved methodologies have evolved for the pretreatment of pseudo reference/secondary electrodes, allowing the equilibration and subsequent use of sensors within <5 minutes as compared with previous requirements for full equilibration from open circuit.
Surfactant modified carbon paste electrode: Part 1: Electrochemical and microscopic characterization
Authors: Digua K. , Kauffmann J.‐M. , Delplancke J.‐L. 
Published: May 2005

AbstractThe modification of the carbon paste electrode (CPE) with the amphiphile hexadecyl sulfonic acid (sodium salt) has permitted the development of a stable and analytically useful functionalized electrode. The electrochemical characterization of the modified electrode (potential range, background current, stability) has been investigated by cyclic voltammetry in aqueous media with different buffer compositions and in hydro‐organic media and the results compared favorably with the conventional carbon paste electrode. The characterization of the sulfonated functionalities and their influence in the electrode behavior has been pointed out using linear scan and adsorptive voltammetry by studying two model compounds: promethazine and ascorbic acid. The marked influence of the pH, ionic strength, and nature of the buffer cation on the shape (potential and intensity) of the voltammetric curves confirmed the structure of the modified electrode interface, i.e., electrode bearing strong cation exchange functionalities. Scanning electron microscopy and optical microscopic observations of the CPE and modified CPE showed a higher density of graphite particles not covered by liquid paraffin at the latter.
Performance test of voltammetric analyzers with a diode based dummy cell
Authors: Yarnitzky Ch. N. 
Published: May 2005

AbstractAn electrochemical dummy cell, consisting of the usual two resistors and a capacitor, and a combination of several diodes simulate diffusion currents in the case of direct current (DC) and differential current measurements. This dummy cell may be used as a qupck electrochemical analyzer tester to determine the electronic noise level and the operation of the different polarographic modes.
Square wave cathodic stripping voltammetric determination of selenium in small quantities of biological tissues
Authors: Prasad Pamidi V. A. , Arunachalam J. , Gangadharan S. 
Published: May 2005

AbstractA sensitive procedure for the determination of selenium in small quantities of biological tissues (5 to 10 mg), using square wave cathodic stripping voltammetry with an in situ formation of Cu2Se on the HMDE, is described. Microwave digestion and clean‐room facilities have been used to prevent the loss of analyte and sample contamination. The method has been standardized through the analysis of NIST SRM 1577 bovine liver. The method offers a detection limit of 1 pg/mL. The average precision of determination at 150 pg/mL of Se is 1.8% RSD. This method is highly suitable for the determination of biopsy samples where the quantity available for the analysis is very limited.
Amperometric glucose biosensor based on a tetrathiafulvalene‐mediated epoxy‐graphite biocomposite
Authors: Céspedes F. , Martínez‐Fábregas E. , Alegret S. 
Published: May 2005

AbstractAn inexpensive, robust, and easily mechanized amperometric glucose senor based on a biocomposite material has been constructed. The biocomposite is made of graphite, a nonconductive epoxy resin, tetrathiafulvalene (TTF) as a redox mediator, and glucose oxidase (GOD). The enzyme retains its bioactivity on confinement in the rigid epoxy‐graphite matrix, with the oxidation current of the reduced mediator serving as the analytical signal (at 150 mV [vs. Ag/AgCl] in a pH 7.00 buffered solution featuring 0.1 M phosphate and 0.1 M KC1). The resulting biosensor shows a linear response in the 0.1 to 2 mM glucose range and produces a steady‐state signal within a few seconds (11 seconds for a 95% response). Simple polishing procedures can be used to regenerate a freshly bioactive transducer surface.
Galvanic sensor for determination of hydrogen sulfide
Authors: Jeroschewski Paul , Haase Karen , Trommer Andreas , Gründler Peter 
Published: May 2005

AbstractA galvanic cell for trace determination of hydrogen sulfide in gases is presented. The cell covers the range from 30 ppb to some hundred ppm. It is characterized by simple construction. The use of ferricyanide/ferrocyanide ions as a redox mediator system ensures very low cross sensitivity. The sensor is well‐suited for mobile use.
The effect of hydrodynamic conditions on the speciation of copper at a chemically modified electrode
Authors: Labuda Ján , Vaníačková Mária 
Published: May 2005

AbstractThe determination of copper in the presence of humic acid and oxalic acid using anodic stripping voltammetry (ASV) at the graphite electrode modified with a copper complexing agents 1‐phenyl‐3‐methyl‐4‐octanoylpyrazol‐5‐on, and a Nafion film is described. The validity of voltammetric criteria for the metal speciation based on the diffusion‐layer thickness and complexing conditions, has been examined. In the copper‐humic acid system, the signal is controlled by diffusion, whereas in the system with oxalic acid, both the dissociation kinetics and diffusion have to be considered.
Detection of electroinactive ions using conducting polymer microelectrodes
Authors: Sadik Omowunmi A , Wallace Gordon G. 
Published: May 2005

AbstractThe detection of electroinactive ions using conducting polymers has been described previously. In this work, we show that the analytical performance of this method is greatly improved using microelectrodes. The use of microelectrodes overcomes the problems associated with the implementation of this detection scheme in low conductivity eluents.