bluuebunny/crossref_metadata_2025 huggingface dataset:
Voltammetric study of the oxine‐based extractant Kelex 100
Authors: Citores M. J. , Alonso R. M. , Fernández L. A.
Published: May 2005

The electroanalytical study of the behavior of 7‐(1′‐vinyl‐3′,3′,5′,5′‐tetramethylhexyl)‐8‐quinolinol, the active component of the commercial extractant Kelex 100 (Ashland Chemicals), at a glassy carbon electrode has been carried out using different voltammetric techniques. The compound is oxidized giving rise to a voltammetric peak in the pH range 1.03–7.27. The plot of the variation Ep versus pH shows two straight lines intercepting at 3.46, which corresponds to the pKai value of the component. The oxidation process of the compound is irreversible (ān = 1.32) and predominantly diffusion controlled, although with an important adsorptive component. The electrode process can be attributed to the oxidation of the hydroxyl group of the quinolinic ring. A voltammetric method for the determination of the extractant has been developed.
Amperometric response of mediating layers on electrode surfaces to Gaussian concentration profiles in flowing streams
Authors: Cassidy John F. , Breen William , McGee Anthony , Vos Johannes G. , Lyons Michael E. G.
Published: May 2005

A model for a layer, containing catalytic centers, coated on an electrode and used for the mediation of analyte in a flowing stream is proposed and solved. The model applies to a situation of a Gaussian concentration profile of analyte impinging on the outer edge of the mediating layer. It was found that the important parameters that limit the current magnitude are the diffusion coefficient of the analyte through the layer, the effective electron diffusion coefficient through the layer and the rate of reaction between the mediator and the analyte. On evaluation of literature data, it was found that layers, high catalyst loading and with high rates of electron exchange, lead to linear peak current height versus concentration plots.
Activation of solid electrodes
Authors: Štulík Karel
Published: May 2005

The mechanical and physicochemical techniques for activation of solid voltammetric electrodes—that is, polishing, chemical, and electrochemical treatment and modification of the electrode surface by heat or electromagnetic radiation—are briefly surveyed and critically evaluated.
Potentiometric anion response of poly (tetrakis(p‐aminophenyl)porphyrin) film‐modified electrodes
Authors: Kliza Dennis M. , Meyerhoff Mark E.
Published: May 2005

The potentiometric response to anions of glassy carbon electrodes coated with thin unmetallated poly(tetrakis(p‐aminophenyl)porphyrin) (poly(H2(p‐TAPP))) films is examined. The polymer films are introduced onto the glassy carbon surface by constant‐potential anodic electrolysis of the porphyrin monomer from a solution of dichloromethane containing a quaternary ammonium perchlorate salt. The thickness of the film is the controlled by the electrodeposition time. Oxidized poly(porphyrin) modified electrodes exhibit near Nernstian response to iodide in the concentration range of 5 × 10−5 – 1 × 10−1 M with significant selectivity over a wide range of other anions tested. The mechanism of the electrode's iodide ion response is considered in light of its response to other redox‐active anions, and a recent literature report describing the selective iodide response of electrodes coated with electropolymerized poly(3‐methylthiophene) films. Spectroelectrochemical studies with poly(porphyrin)‐modified tin oxide electrodes are used to confirm the redox‐type response mechanism of the sensors toward iodide. The analytical limitations of using such polymer film‐modified electrodes for potentiometric ion sensing are discussed.
Mediated micro‐glucose sensors using 2 μm platinum electrodes
Authors: Yokoyama Kenji , Nakajima Kenji , Uchiyama Shunichi , Suzuki Shuichi , Suzuki Masayasu , Takeuchi Toshifumi , Tamiya Eiichi , Karube Isao
Published: May 2005

Glucose‐oxidase (GOD) and glucose‐dehydrogenase (GDH) immobilized cylindrical microelectrodes were fabricated, and their characteristics were evaluated by using 1,4‐benzoquinone and ferricyanide as electron mediators, respectively. Each enzyme was immobilized in a photocrosslinkable polymer on a cylindrical microelectrode of 2 μm diameter. A linear range in the calibration plot of the GOD‐based micro‐glucose sensor was observed to be wider than that obtained using a disk electrode of 1 mm diameter. The mediated response of the 2 μm glucose sensor was compared with the response resulting from hydrogen peroxide detection. This result showed that a higher response and a wider linear range were observed at a highly concentrated mediator. For the GDH‐immobilized 2 μm microelectrode, a much higher response was obtained when not only ferricyanide but also diaphorase were employed to reoxidize NADH produced by the enzyme reaction of GDH. The GDH‐based micro‐glucose sensor was found to be unaffected by dissolved oxygen concentration.
Nafion‐coated carbon fiber for acetylcholine and choline sensors
Authors: Navera Eriberta Nepomuceno , Suzuki Masayasu , Tamiya Eiichi , Takeuchi Toshifumi , Karube Isao
Published: May 2005

A major improvement in the selectivity of carbon fiber microelectrodes for acetylcholine (Ach) and choline (Ch) as cationic amines is described. The electrodes are coated with Nafion, a perfluorosulfonated polymer. This coating is practically impermeable to ascorbic acid (AA) and anionic biogenic amine metabolites. Nafion‐coated fiber was characterized by cyclic voltammetry (CV). Selectivity and the dynamic range of these coated electrodes were evaluated using amperometric determination at a fixed potential of 1.2 V. The esterase activity was determined using choline sensor, and the relative slope values showed a fast response between 1 and 3 minutes. Calibration plots for Ach and choline showed a linearity range between 0.1 and 3 mM, with an increase of two orders of magnitude better than the previously used PVA‐SbQ membrane. No response was obtained between 0.1 and 0.3 mM of AA conc. The procedure, in preparing this type of coated electrodes, indicates some attractive perspectives for its use, especially for in vivo monitoring.
Neuronal biosensors: A progress report
Authors: Leech Dónal , Rechnitz Garry A.
Published: May 2005

A review of the progress of research in the development of intact chemoreceptor‐based biosensors is presented. These sensors utilize the chemosensing ability of the antennules of various decapod crustacea to sensitively and selectively detect chemical stimulants. Suction microelectrodes attached to the antennular nerve fibers are used to detect action potential firing upon binding of the stimulant to the receptor, allowing quantitation of the analyte. Recent developments in the use of different species and in improvements in experimental setup, data handling procedures, and sensor lifetimes are reported.
Anodic stripping voltammetry of copper in natural waters: A qualitative approach to the additional peak(s) occurrence
Authors: Boussemart Marc , Menargues Luc , Benaïm Jean‐Yves
Published: May 2005

In the presence of natural organic species, the electrochemical behavior of metals can be modified. Several authors have already noticed an extra peak or shoulder in the Cu peak during anodic stripping voltammetry (ASV) analysis, but the origin of this interference was generally not investigated and the experimental conditions were modified to make it disappear. In this article, this phenomenon alone was studied. The organic matter dissolved in interstitial waters of marine sediments was fractionated by ultrafiltration and gel permeation chromatography. The resulting fractions were qualitatively studied with respect to the complexity of the voltammograms they exhibit during an ASV analysis of Cu. Very similar electrochemical behaviors (multiple peaks) were found for interstitial waters and humic substances. The fractionation experiment suggests that particular families of molecules, which can be separated, are responsible for these extra peaks. Therefore, the “multipeak” phenomenon is related to the quality of the organic matter rather than to its quantity. This fact, supported by several experiments [DPASV, differential pulse polarography (DPP)], has led to a model which, although still somewhat speculative, describes well the usual observations: the extra peaks would originate from the oxidation of organic copper species [most likely as Cu(I)] adsorbed and stabilized on the mercury drop electrode.
Glassy carbon electrodes coated with electropolymerized resole prepolymer mixtures: Amperometric response to phenols and application as chromatographic sensors
Authors: Ortiz Patricia I. , Nader Paul R. Abu , Mottola Horacio A.
Published: May 2005

Resole mixtures made with phenol, 4‐hydroxybenzaldehyde, and 4‐hydroxybenzoate electrochemically generate films that protect glassy carbon surfaces from poisoning. The high oxygen content of these films mimics the surface characteristics of activated carbon electrodes and permits their continuous use for detection in flowing streams. The amperometric response of different phenolic materials at these chemically modified surfaces and their liquid chromatographic application as electrodes in thin‐layer cells are reported. Comparative considerations using a post‐column enzyme reactor and redox‐mediated electrochemical detection are also presented.
Cathodic stripping voltammetric measurements of cholesterol following adsorptive preconcentration at the static mercury drop electrode
Authors: Tuzhi Peng , Huiping Li , Rongshan Lu
Published: May 2005

A new electrochemical method for direct measurement of cholesterol by cathodic stripping voltammetry is presented. The method is based on controlled adsorptive preconcentration at the static mercury drop electrode, followed by differential pulse voltammetric determination, in which adsorbed cholesterol reduces and shows stripping current at ca. −1.04 V (versus Ag/AgCl). The current was linear with the cholesterol concentration in the range of 0.2–8 μM. The detection limit found was 0.02 μM (10 minute preconcentration), and the relative standard deviation (at 0.6 μM level) 4.6%. Cyclic voltammetry was used to explore the adsorptive and electrochemical behavior. The adsorptive stripping response was evaluated with respect to preconcentration time, concentration dependence solution, stripping model, possible interference, and other variables. Applicability to serum analysis was illustrated.
In situ voltammetric measurements in natural waters: Future prospects and challenges
Authors: Tercier M.‐L. , Buffle J.
Published: May 2005

The state of the art and challenges in developing in situ voltammetric probes for direct measurements in natural waters are presented. Articles dealing with this topic are reviewed. Use of voltammetric probes in the laboratory and in the field is outlined. An up‐to‐date account of the results reported in the literature on the development of existing in situ voltammetric systems for such measurements is given. Emphasis is placed on the need for such systems to gain a better understanding of the mechanisms of processes occurring in natural aquatic systems. Suggestions are made for future development.
Digitally simulated predictions of the voltammetric current response relative to adsorbed enzyme‐modified electrodes
Authors: Randriamahazaka Hyacinthe , Nigretto Jean‐Maxime
Published: May 2005

Digital simulation has been used to model the current response of an enzyme‐partially coated solid electrode. Enzymatic activities were detected using cyclic voltammetry by monitoring the release with time of a redox label split from a substrate contained in the solution. The predicted calibration curve indicated that, depending on the value of the catalytic rate constant, the different trends observed were controlled either by pure diffusion, by pure catalysis, or by a combination thereof. A procedure to attain the pertinent kinetic and diffusion properties affecting this system is given.
Determination of nitrite ions in well water by biamperometric standard addition
Authors: Lichtig Jaim , de Oliveira Rezende Maria Olímpia
Published: May 2005

A new modified biamperometric method of analysis is proposed which has the advantage of producing straight lines as plots. Nitrite ions in well water have been determined by biamperometry and standard addition of solutions containing nitrite or iodate ions. Two platinum foils are immersed in the solution and 100 mV potential is applied between the electrodes; the resulting current is measured. The standard nitrite or iodate ions react with excess of iodide ions, producing triiodide. The reversible redox pair I/I−is responsible for a change in current, allowing the biamperometric measurement. The concentration of triiodide formed depends on the nitrite concentration. Twenty ppb of nitrite ions have been determined with good accuracy and precision. EDTA was added to eliminate interference from Fe(III), Cu(II), and other metal ions.
Applications of adsorptive stripping voltammetry in the determination of trace and ultratrace metals
Authors: Paneli Miropi G. , Voulgaropoulos Anastasios
Published: May 2005

Recent advances in adsorptive stripping voltammetry (AdSV) are reviewed. The mechanisms of the adsorptive and stripping steps are given. The criteria of ligand selection, along with the present status and future trends in AdSV for trace element analysis, are discussed. Tables containing the elements determined by AdSV and the ligands used in AdSV, as well as the real samples analyzed and operational conditions, are presented (together with 171 references).
Monoalkylferrocene‐mediated amperometric enzyme electrodes for glucose determination
Authors: Razumas Valdemaras , Kulys Juozas , Knichel Martin , Wiemhöfer Hans‐Dieter , Göpel Wolfgang
Published: May 2005

Amperometric biosensors for the determination of β‐D‐glucose are described. Glucose‐sensitive graphite electrodes are prepared by adsorptive immobilization of n‐butylferrocene (n‐BFc), ter‐butylferrocene (t‐BFc), or ethylferrocene (EFc). Glucose oxidase from Aspergillus niger is immobilized on the monoalkylferrocene‐modified surfaces of the graphite electrodes by covalent attachment. The biosensors based on n‐BFc, t‐BFc, and EFc could be used at potentials of 0.3, 0.325, and 0.275 V, respectively (vs. SCE reference electrode). A linear steady‐state current response, proportional to the glucose concentration in a range of 1–20 mM, is observed for the t‐BFc‐ and EFc‐mediated enzyme electrodes. Data are presented on the influence of potential, oxygen, pH, and temperature upon the electrodes. Results are discussed on the basis of the structural features of the mediators.
Studies on the voltammetric behavior of a bismuthiol I‐containing carbon paste electrode: Determination of traces of bismuth
Authors: Cai Xiaohua , Kalcher Kurt , Magee Robert J.
Published: May 2005

The voltammetric behavior of a bismuthiol I‐containing carbon paste electrode was studied. Bismuthiol 1 is electroactive, when mixed with carbon paste as an electrode modifier, and is oxidized at 0.3 V and re‐reduced at −0.6 V (vs. SCE). Nevertheless, it can be used as a modifier of carbon paste electrodes for the preconcentration and subsequent voltammetric measurement of bismuth, if suitable measurement conditions for the analysis are met. Bismuth(III) can be preconcentrated from acidic solutions onto this electrode under open circuit conditions. Linearity between current response and concentration can be achieved for 0.005 to 4 μg/ml bismuth using cathodic differential pulse voltammetry after preconcentration for 0.5 or 2 minutes. The interferences as well as various parameters for the preconcentration and measurement of bismuth(III) were investigated.
Optimization of conditions for mercury‐coated carbon fiber electrode formation and their influence on the cathodic stripping voltammetry of Se(IV)
Authors: McLaughlin Kieran , Rodriguez Jose Ramon Barreira , Garciá Augustin Costa , Blanco Paulino Tuñón , Smyth Malcolm R.
Published: May 2005

The conditions for the deposition of mercury on the surface of carbon fibers to permit the sensitive and reproducible voltammetry of Se(IV) have been investigated. Several procedures employing both predeposition and in situ formation of a mercury film on the carbon fiber were evaluated, and the effect of the mercury concentration and plating time upon the sensitivity of the stripping response for Se(IV) was determined. Due to the steady‐state diffusional mass transport characteristics exhibited by these electrodes, the need for stirred solutions, a specific deposition potential, and a deposition time period in the stripping voltammetric procedure was eliminated. This procedure gave rise to a linear response up to 3 ng/ml, a detection limit of 0.11 ng/ml, and a relative standard deviation (RSD) of 4.4% at 5 ng/ml (n = 5) for determination of Se(IV).
Macrocyclic oxamides as ionophores for lead‐selective membrane electrodes
Authors: Malinowska Elzbieta , Jurczak Janusz , Stankiewicz Tomasz
Published: May 2005

A set of macrocyclic oxamides intended to be used as potential ionophores for lead ions in solvent polymeric membrane electrodes was investigated. The influence of the structure of ligands (number and distribution of oxygen donor atoms and ring size) on the selectivity was examined. Pronounced preference of lead over other divalent and some monovalent cations was observed for the 21‐membered‐ring oxadiamides (ionophores 1 and 7). These electrodes exhibited a linear response within the activity range of 10−5.4 −10−15 M in Pb(NO3)2 solutions.
Voltammetric determination of the antidepressant trimipramine at a lipid‐modified carbon paste electrode
Authors: Khodari Mahmoud
Published: May 2005

The voltammetric behavior of trimipramine at a carbon paste electrode (CPE) modified with some fatty acids is investigated. This hydrophobic drug is accumulated at the electrode by a combined adsorption/extraction process, with greatly enhanced response over the unmodified paste. The linearscan response was characterized with respect to preconcentration period, pH, paste composition, reproducibility, possible interferences, and other variables. The detection limit was found to be 1 × 10−9 M. The determination of trimipramine in urine required no pretreatment other than dilution with phosphate buffer and medium exchange technique.
A new application of fast green in catalytic analysis—catalytic determination of ultratrace ruthenium with oscillopolarographic detection
Authors: Zhiliang Jiang , Chen‐zhen Qin
Published: May 2005

Experiments show that ruthenium [Ru(III)] has a very strong catalytic effect on the slow redox reaction between fast green (FG) and potassium periodate in hydrochloric acid medium, and that FG exhibits a sensitive single‐sweep oscillopolarographic wave at −0.56 V (versus SCE) in the pH 3.9 of acetate buffer solution. The oscillopolarographic behavior has been investigated. A novel, highly sensitive, and selective catalytic reaction‐oscillopolarographic method for Ru has been proposed according to the Ru(III) catalytic effect on the reaction. A detection limit of 0.27 ng/L and a calibration graph from 0.8 to 40 ng/L Ru were obtained by the fixed‐time procedure. Ruthenium in an ore sample was determined by this method with excellent results.
Study on the electrooxidation of biliverdin by in situ thin‐layer spectroelectrochemistry
Authors: Niu Jianjun , Dong Shaojun
Published: May 2005

The electrooxidation reaction of biliverdin (BV) is studied by in situ spectroelectrochemistry with rapid spectra scanning in an optically transparent thin‐layer cell. The study reveals that the oxidation process of BV is very complicated and involves many stages. The average formal potential of BV is obtained for the first time as E°′ = 0.634 V (vs. Ag/AgCl), and the electrooxidation mechanism of BV is proposed.
Controlled electrochemical preparation of enzymatic layers for the design of amperometric biosensors
Authors: Coche‐Guerente Liliane , Cosnier Serge , Innocent Christophe , Mailley Pascal , Moutet Jean‐Claude , Morélis Renée M. , Leca BÉAtrice , Coulet Pierre R.
Published: May 2005

A newly synthesized pyrrole derivative was used for enzyme entrapment on carbon or platinum electrodes by electropolymerization. Three enzymes were tested: glucose oxidase (GOD), tyrosinase, and choline oxidase. Contrary to other techniques using electropolymerization in solution, a drop of enzyme‐monomer mixture was deposited and allowed to dry on the electrode surface before the electropolymerization. This procedure enables one to control the amount of entrapped enzyme and to easily obtain multilayer assemblies.
Self‐assembled lipid bilayers as a potassium sensor
Authors: Rehák Marián , Šnejdárková Maja , Otto Matthias
Published: May 2005

The effect of valinomycin on a novel bilayer lipid membrane (BLM) system supported on a metallic wire (s‐BLM) has been investigated. An increase in concentration of valinomycin from 6 × 10−6 to 6 × 10−4 mol L−1 increases the conductivity of the system after addition of potassium ions. A remarkable effect of the buffer medium on the electrode response has been observed, a solution of 0.1 M Tris‐HCl being most suitable. The assembled electrode system is stable for about 120 hours. A linear response toward potassium has been found in the range from 2.5 × 10−3 to 1.3 × 10−1 mol L−1. Effect of pH, temperature, and possibly interfering substances are reported.
Cyclic voltammetry of ferrocenecarboxylic acid monomolecular films and their reaction with glucose oxidase
Authors: Barmin Anatoli V. , Eremenko Arkadi V. , Kurochkin Ilya N. , Sokolovsky Andrei A.
Published: May 2005

Monomolecular films of ferrocene derivatives (FD) and of glucose oxidase (GOD) have been formed on a graphite electrode by the Langmuir‐Schaefer (LS) method with the help of amphiphilic polymers. Cyclic voltammograms of these films and of their interaction with glucose oxidase were studied. Ferrocenecarboxylic acid, incorporated into polymeric matrices by adsorption to a monomolecular polymer film or by the direct mixing with a polymer solution before LB‐film formation, retain their mediator properties in the reaction with GOD. The amperometric response of a graphite electrode with immobilized multilayer films containing polymer matrices, ferrocenecarboxylic acid and GOD were linear over the range 1–20 mM of glucose.
Crown ethers in stripping voltammetry of palladium
Authors: Tsymbal Maria V. , Tuijan Iva Ya. , Temerdashev Zaual A. , Brainina Khjena Z.
Published: May 2005

The similarity in the structures (presence of hexatomic rings) of crown ethers and graphite is used for adsorptive modification of the graphite electrode surface. The effect is exploited in stripping voltammetry for the determination of palladium. Anodic currents observed at potentials of 0.6 to 0.65 V (vs. Ag/AgCI electrode) are the source of information about adsorption of the crown ethers. Maximum adsorption of the reagents takes place at potentials close to the potential of zero charge of graphite. Deposition of palladium on the electrode surface is enhanced, the closer the values of the diameters of the crown‐ether rings and Pd(II) are.
The influence of electrolyte media on the cathodic stripping voltammetry of lead dioxide on glassy carbon electrode
Authors: Velayutham D. , Noel M.
Published: May 2005

The influence of three electrolyte media, namely, acetate buffer, nitric acid, and perchloric acid, on cathodic stripping of lead dioxide at a glassy carbon electrode (GCE) was studied using cyclic voltammetry (CV) and linear sweep stripping voltammetry (LSSV) techniques. One M acetic acid/1 M sodium acetate, 0.1 M nitric acid, and 0.1 M perchloric acid were found to give a sharp cathodic stripping voltammetric (CSV) response. Various factors, such as concentration of supporting electrolyte, depositior, potential (Edep) deposition time (tdep), and concentration of Pb2+ (C), are also presented and discussed. The lowest detection limit of Pb2+ in acetate buffer is 5 × 10−8 M and, in 0.1 M nitric acid and 0.1 M perchloric acid, is 1 × 10−5 M. The influence of medium on cathodic stripping peak broadening is analyzed in detail. It is concluded that the formation of insoluble intermed ates is the major cause for peak broadening, and the ability of the supporting electrolyte anion to inhibit the formation of such intermediates, through complexation, is the major reason for sharper stripping voltammetry response.
Determination of lead in microliter amounts of whole blood by stripping potentiometry
Authors: Jagner Daniel , Renman Lars , Wang Yudong
Published: May 2005

Lead in whole blood is determined using a commercial potentiometric stripping analyzer in combination with a portable personal computer and a new electrode design permitting rotation of the sample. A 70 μL blood sample is added to 200 μL distilled water contained in a disposable test tube. After mixing, 400 μL of a matrix‐modifying solution containing hydrochloric acid, mercury (II) ions, Triton X‐100, and bismuth (III) as an internal standard, is added to the sample which is then transferred to the sample holder. Lead amalgam is deposited on the glassy carbon electrode by means of a pulsed potential cycle for 3 minutes after which lead is reoxidized by means of a constant current. The complete electroanalytical procedure, including result evaluation by means of the internal standard, and graphical display is under computer control. For ca. every 15th sample, the instrument is recalibrated, if necessary, using two whole blood standards. The relative precision is ca. 10% and the detection limit 3.5 μg/L. The stripping potentiometry results agree well with the results obtained by inductively coupled plasma mass spectrometry in the analysis of whole blood from individuals occupationally exposed to lead and with the results obtained by graphite‐furnace atomic spectroscopy in the analysis of whole blood from 141 school children.
Kinetic studies on membraneless amperometric biosensors prepared from xanthine oxidase, organic conducting salt, and silicone oil
Authors: Korell Ulrich , Spichiger Ursula E.
Published: May 2005

Membrane‐free amperometric biosensors have been prepared from xanthine oxidase powder (XOD) (E.C.1.2.3.2) the organic conducting salt TF‐TCNQ, and silicone oil The sensor response to hypoxanthine can be described by the ezyme‐kinetic Michaelis‐Menten formalism with good correlation over a wide range of potential (–100 tc +300 mV vs Ag/AgCl) and pH (6.10 to 8.80)values. Measurements with rotating disk rotating disk electrodes reveal that XOD is oxidized by at least two transfer to the mediators so that the sensor can be operated in air‐saturated solution. Since open circuit conditions alter the kinetic parameters of the sensor, operation in flow analysis systems is recommended. Analytical features including response time (t95 ≈ 10 seconds), detection limit (ca. 10 nM hypoxanthine), selective over interferents (e.g., ascirbate), and simplicity of preparation as well as operation and storage stability compare very favorably with other OXD biosensors.
Effect of electrochemical pretreatment on protein adsorption at glassy carbon electrodes protein
Authors: Downard Alison J. , Roddick Alisa D.
Published: May 2005

Three types of electrochemical, pretreatments (ECPs) were assessed as a means of reducing albumin adsorption at glassy carbon electrodes. The cyclic voltammetric and differential pulse responses of the probe analyte, ferrocenemonocarboxylic acid (FCA), in the absence and presence of 4 g L−1 bovine serum albumin (BSA) were used to monitor protein adsorption at pretreated electrodes. Severe dc pretreatment in acid increased BSA adsorption (compared to that at a polished electrode), whereas square‐wave pretreatment in aqueous NaCl and dc pretreatment in base both reduced the amount of BSA adsorption. The effects of the latter two ECPs on the response of acetaminophen in the presence of BSA were examined. The loss of sensitivity in the presence of BSA was reduced at electrodes which were pretreated. However, our results sugges: that ECP which leads to very strong accumulation of analyte may have a deleterious effect on electrode performance in the presence of protein.
Permeation of solutes through an electropolymerized ultrathin poly‐o‐phenylenediamine film used as an enzyme‐entrapping membrane
Authors: Centonze Diego , Malitesta Cosimino , Palmisano Francesco , Zambonin Pier Giorgio
Published: May 2005

Permeation of electroactive organic probes through an electroinactive and passivating poly‐o‐phenylenediamine (PPD) film electropolymerized on Pt and glassy carbon (GC) electrodes has been investigated by cyclic and rotating disk electrode (RDE) voltammetry. The access of solutes to the metal‐polymer interface appears mainly governed by specific chemical interactions, influencing partition, and diffusion phenomena, rather than by exclusion effects based on molecular size or charge. Potential cycling of the film induces fine modifications in the chemical/physical structure of the polymer, as evidenced by electron spectroscopy for chemical analysis (ESCA) measurements and by an enhanced permeation of certain solutes. The membrane is, however, stable in the pH and potential range usually employed in its application, that is, as an enzyme‐entrapping membrane in amperometric biosensors; because of membrane permselectivity, the electrochemical response of the most common electroactive interferents is deeply depressed.
Improved performance of carbon paste amperometric biosensors through the incorporation of fumed silica
Authors: Wang Joseph , Naser Najih
Published: May 2005

The 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

The 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

A 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

This 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

The 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

Voltammetry 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

A 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

The 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

The 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

Different 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

An 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

The 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

The 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

Theoretical 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

Cathodic 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

Four 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

The 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

Glucose, 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

This 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.