bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous measurement of plasma serotonin, catecholamines, and their metabolites by an in vitro microdialysis‐microbore hplc and a dual amperometric detector
Authors: Cheng Fu‐Chou , Lin Nai‐Nu , Kuo Jon‐Son , Cheng Lee‐Ju , Chang Fang‐Mai , Chia Lie‐Gan 
Published: May 2005

AbstractMany advantages of a method for the simultaneous measurement of plasma norepinephrine (NE), epinephrine (E), dopamine (DA), 3,4‐dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin, and 5‐hydroxyindole‐3‐acetic acid by the in vitro microdialysis‐microbore high‐performance liquid chromatography‐electrochemical detection (MD‐MHPLC‐ED) technique have been described in our previous article. The present experiment uses a dual electrode electrochemical detector (DUED) in the MD‐MHPLC system, providing an additional reliable measurement or assignment of peaks by identifying the peaks based on their redox ratios at the oxidation/reduction cycle. Thus, the important early eluting front and interfering peaks were eliminated on the cathodic chromatogram. Within 15 minutes, an isocratic separation of these analytes is achieved by using microbore column. Hence, theoretically, over 90 analyses can be performed in a single working day. The detection limit (S/N = 3) of this method was about 0.2 to 0.5 pg per injection. The required volume of plasma samples is less than 200 μL. Thus, blood loss is minimal with repeated blood sampling, especially in experiments using small animals. This simple, efficient, and sensitive method can, therefore, be used as a basic research tool in the investigation of blood biogenic amines and their metabolites.
A polarographic investigation on interactions between cu(ii) ions and natural degradation products of a herbicide atrazine
Authors: Grabec Irena , Ogorevc Božidar , Hudnik Vida 
Published: May 2005

AbstractA study was performed to investigate the possible formation of coordination compounds between Cu(II), Cd(II), Zn(II), and Pb(II) ions and natural degradation products of atrazine (ATR) desisopropylatrazine (DIA), desethylatrazine (DEA), and desethyldesisopropylatrazine (DEIA), as well as parent compound ATR itself and the related s‐triazine herbicide prometryne (PRO). By using polarographic and voltammetric titrations of a metal ion with a ligand and vice versa, at mercury drop or plain carbon paste electrode, only a formation of coordination compounds involving Cu(II) ions, of a type CuL2 (L = DEA, DIA, and PRO) and CuL (L = DEIA) in aqueous solutions at pHs above 4, were observed. By applying an indirect polarographic method with ligand exchange (EDTA), a conditional stability constant of CuDEIA was determined, and the value β CcuDEIA = 12.7 was obtainted.
Condensation α‐cyclodextrin polymer membrane with covalently immobilized glucose oxidase and molecularly included mediator for amperometric glucose biosensor
Authors: Kutner Wlodzimierz , Wu Huihuang , Kadish Karl M. 
Published: May 2005

AbstractA highly permeable film of the condensation α‐cyclodextrin polymer (α‐CDP) was used as a membrane for fabricating a “second‐generation” glucose amperometric biosensor. Glucose oxidase (GOD) was covalently immobilized, whereas 1,4‐benzoquinone (BQ), or tetrathiafulvalene (TTF) mediator molecules were included in the membrane by the α‐cyclodextrin sites. A simple one‐step procedure for the biosensor preparation was developed. It consisted of casting the membrane onto the surface of a glassy carbon, gold, or platinum disk substrate from an aqueous solution, pH 2.0 (HCl), containing equimolar quantities of a water‐soluble α‐cyclodextrin prepolymer, a glutaric dialdehyde cross‐linking reactant, GOD, and the mediator. Cyclic voltammetry (CV) limiting currents for glucose biocatalytic electrooxidation were measured for different enzyme loadings and mediator dosings inside the membrane as well as for different glucose conoentrations in a (0.1 M phosphate buffer + 0.1 M NaClO4) pH 7.0 solution. The limiting‐electrocatalytic currents at the (α‐CDP)‐GOD‐TTF electrode were pH independent and occurred atE1/2= 0.03 V (vs. SCE), i.e., at a favorably low potential value. The detectability of glucose was 10 μM for the (α‐CDP)‐GOD‐BQ electrode at the 2 mg (18.5 unit) GOD loading and a signal‐to‐noise ratio of 3. The values of apparent Michaelis constant for glucose and the maximum limiting electrocatalytic current density, determined from the Michaelis‐Menten analysis for the 1 mg (18.5 unit) GOD loading, were (4.5 ± 0.5) mM and (190 ± 20) μA cm−2for the (α‐CDP)‐GOD‐BQ electrode, and (5.6 ± 0.8) mM and (137 ± 16) μA cm−2for the (α‐CDP) GOD‐TTF electrode, respectively. The sensor performance was examined with respect to the method of membrane preparation, membrane composition, and long‐term stability. Miniaturization of the biosensor is facile if, for instance, a 10 μm Pt disk microelectrode substrate is used.
Evaluation of a new solid‐state reference electrode junction material for ion‐selective electrodes
Authors: Diamond Dermot , McEnroe Eamonn , McCarrick Mary , Lewenstam Andrzej 
Published: May 2005

AbstractThe performance and properties of a new low‐resistance material, Refex, suitable for use in reference electrode junctions is described. The material is a solid polyvinyl acetate that contains a very‐ large loading of KCl (1:1 w/w KCI/PVA). Despite relatively large active surface areas in the designs studied (stand‐alone reference and combination pH), leakage rates of KCl are remarkably low. pH measurements in ultrapure water and comparative measurements in common buffer solutions against standard reference electrodes confirm the stability of the potential developed across the junction to be very stable. Impedance studies verify the importance of the KCl doping for realization of the low resistance and attractive electrochemical properties of the material.
Determination of aluminum ions by indirect potentiometry in a flow system
Authors: Ngila J. Catherine , Alexander Peter W. , Hibbert D. Brynn 
Published: May 2005

AbstractA potentiometric system is described for the indirect flow determination of Al3+ with an aluminum wire as indicator electrode. The method is based on the reaction between aluminum and fluoride ions at pH 5.0 in acetate buffer. The reduction in activity of fluoride ions is detected by the aluminum electrode. The response was optimized for the flow rate of solution, length of reaction tubing, concentration of fluoride reagent, and pH of the buffer. The response was linear with concentration of aluminum in the range of 0.5 to 50 ppm with a relative standard deviation (RSD) of 0.7%. There was negligible interference from a range of cations and anions when their concentrations were less than 20 ppm.
Determination of CD, CU, and PB in animal tissues—comparison of electrochemical results obtained with a new polarographic system and atomic spectroscopy
Authors: Šestáková Ivana , Miholová Daniela , Slámová Alžběta , Mader Pavel , Száková Jiřina 
Published: May 2005

AbstractReference materials of animal origin have been analyzed for Cd, Cu, and Pb contents by voltammetry using ECO‐TRIBO Polarograph with pentype renewed Hg electrode after dry ashing in superoxidizing atmosphere (mixture of O3 + O2 + NOx). The contents of all metals mentioned were independently determined in aliquots of identical digests by atomic absorption spectrometry (AAS). Statistical evaluation showed good correlation between both methods. Moreover, dectrochemical results the obtained for biological certified reference material (CRM) 12‐02‐01 Bovine Liver are in very good agreement with certified values for Cd and Pb.
On the electrochemical oxidation of 5‐hydroxy barbituric acid
Authors: Berchmans Sheela , Vijayavalli R. 
Published: May 2005

AbstractThe electrochemical behavior of 5‐hydroxy barbituric acid (HB) has been investigated in aqueous and nonaqueous media. In aqueous medium, there is only one anodic peak at –50 mV (at v = 20 mV/s), and no cathodic peak is observed indicating an irreversible reaction under the conditions of this study. The cyclic voltammograms indicate a two‐electron transfer reaction corresponding to the oxidation of HB to alloxan monohydrate (AM). In nonaqueous medium, voltammetric response is observed both in the anodic as well as the cathodic directions. The anodic peak occurs at +140 mV and the cathodic peak occurs at –320 mV at v = 20 mV/s. At high scan rates (v > 200 mV/s) there are two cathodic peaks. The mechanism of oxidation of HB is discussed, and the rate constants of the reaction are calculated.
Characterization of a wall‐jet electrode/flow‐injection analysis system
Authors: Huang Yu Liang , Khoo Soo Beng , Yap Miranda G. S. 
Published: May 2005

AbstractA “wall‐jet” electrode (WJE) was studied as an electrochemical deteaor for flow‐injection analysis (FIA). Mathematical expressions were obtained for the peak current responses of the electrode, both for an uncoiled open tubular conduit and also in the presence of a packed‐bed reactor between the injection valve and detector. The derived relationships between peak current and volumetric flow rate, and injected sample volume and concentration of the analyte were verified by using the ferricyanide ion and hydrogen peroxide as test samples. In general, theory and experiment were in good agreement although a discrepancy in the volumetric flow rate dependence of the peak current was observed in the presence of a packed‐bed reactor.
Determination of epinine in human urine by high‐performance liquid chromatography coupled with electrochemical detection using carbon fiber microelectrodes
Authors: Hua Chi , Lee Hian Kee , Hsieh An Kong 
Published: May 2005

AbstractEpinine was detected with a simple and disposable carbon fiber flow electrode after being separated by high‐performance liquid chromatography (HPLC). An alumina adsorption procedure was used for the extraction of epinine from urine samples. The extraction recoveries at 1, 3, and 6 μg/mL epinine concentration levels were 66.9 ± 3.7, 65.6 ± 3.3, and 67.0 ± 3.4%, respectively (n = 5). Linear responses to epinine in urine were obtained over the range of 0 to 10 μg/mL. The detection limit (signal‐to‐noise ratio = 5/1) for epinine in urine was 15 ng/mL.
Differential pulse polarography of some organic peroxides
Authors: Salvato B. , Jambon C. , Vittori O. , Rochefort O. 
Published: May 2005

AbstractSeveran organic peroxides were studied by differential pulse polarography (DPP) in water and water–solvent media, and compared to hydrogen peroxide. Reduction occurred usually between −0.1 and +0.3 V vs. SCE, except for the peroxides containing a tert‐butyl group adjacent to the OO function. In this case, reduction was more difficult and was shifted to the −0.9 to −1.1 V vs. SCE range. Diffusion coefficients were determined and are in the 4 − 9 × 10−10 m2 s−1 range. The detection limits are generally no lower than 5 × 10−5 mol l−1, due to the high irreversibility of the reduction process. Calibration plots from 5 × 10−5 to about 5 × 10−4 mol l−1 exhibit very good linearity.
Amperometric detection of the ammonium ion by facilitated ion transfer across the interface between two immiscible electrolyte solutions
Authors: Osborne Murray D. , Girault Hubert H. 
Published: May 2005

AbstractFacilitated ion transfer reactions of the ammonium, potassium, and sodium ions with the ionophores dibenzo‐18‐crown‐6, nonactin, and valinomycin were investigated at the water/ 1, 2‐dichloroethane interface. Association constants for the various reactions studied were calculated to determine the selectivity imparted by the ionophores on the transferring ions. Of the ionophores studied, nonactin was found to be the most selective towards the ammonium ion, with a calculated association constant of 14.1.
Flow injection potentiometric determination of harmine and harmaline hallucinogens
Authors: Hassan Saad S. M. , Elnemma Eman M. , Hamada Marawan A. 
Published: May 2005

AbstractFlow injection analysis (FIA) systems incorporating potentiometric sensors for harmine and harmaline hallucinogens are described. The sensors are based on the use of harmine and harmaline tetraphenylborate or reineckate as electroactive compounds dispersed in plasticized PVC matrix. Laboratory‐build flow‐through sandwich cell equipped with silver disk coated with the sensing material is used as a detector in a low dispersion FIA system. The detector exhibits fast and linear response over the concentration range 10−2−10−6 M harmine or harmaline with a detection limit of 2 μg/mL (for 100 μL samples). Operational pH ranges from 3 to 8, sampling rate is 80 per hour and the precision is typically ±0.6%. Recovery and reproducibility data agree fairly well with those obtained by gas–liquid chromatography.
Stable layers of oxyethylated iso‐octylphenols adsorbed on the surface of a hanging mercury drop electrode under tensammetric conditions
Authors: Pawlak Maria Krystyna 
Published: May 2005

AbstractThe stability of films of oxyethylated alkylphenols of the Triton X series on the hanging mercury drop electrode was investigated. The stability of the adsorbed layers increases upon increasing the concentration of the substance. More stable films were obtained after saturation of the electrode surface with monomeric forms. The stability of the film increases in the presence of associated forms.
Electroactive coatings of dicyano‐bis(1,10‐phenanthroline)iron(II) attached to Nafion polymer film modified electrodes via adsorption
Authors: Li Huimei , Li Yijun , Li Jinghong , Wang Erkang , Dong Shaojun 
Published: May 2005

AbstractA dicyano‐bis(1,10‐phenanthroline)iron(II)/Nafion modified elecrode was prepared. The voltammetric and the spectroelectrochemical behavior of this electrode were investigated. The influence of pH and the amount of Nafion and dicyano‐bis(1,10‐phenanthroline)iron(II) (DBPI) used in the electrode preparation on the electrochemical behavior is presented.
Study of the adsorptive voltammetric behavior of the RhIII–5–Br–PADAP complex
Authors: Wang Chunming , Hong Chunlin , Li Hulin 
Published: May 2005

AbstractThe adsorptive voltammetric behavior of the RhIII–2–(5–bromo–2–pyridylazo)–5–diethylaminophenol (5–Br–PADAP) complex was studied with the linear scan technique in a solution of 0.01 mol/L NaOAc‐0.07mol/L HOAc–35% ethanol (supporting electrolyte, pH 4.2).A very sensitive and selective adsorptive stripping voltammetric method for the determination of Rh is described. The proposed method can be used for determining trace rhodium in the concentration range 7.8 × 10−9–9.7 × 10 −7 mol/L without interference from other noble metal ions. At the same time, a simple oscillopolarographic procedure for determining Rh in the same electrolyte is also proposed.
Investigating polymers and conducting metals as transduction mediators or immobilization matrices
Authors: Hall Elizabeth A. H. , Skinner Nigel G. , Jung Christoph , Szunerits Sabine 
Published: May 2005

AbstractAn equivalent circuit, which extends the Randles model to include coupled chemical steps, is considered for a finite diffusion layer, describing synthetic metals. Information was used, concerning the effect of interaction of solution species on the layer circuit, together with complimentary kinetic parameters from a nonlinear least squares fit to the dispersion data, of two‐dimensional model functions, to study the glucose induced response of polyaniline and NMP.TCNQ in glucose oxidase loaded synthetic metals.
Microfabrication technology of flexible membrane based sensors for in vivo applications
Authors: Buck Richard P. , Cosofret Vasile V. , Lindner Erno , Ufer Stefan , Mudaras Marcel B. , Johnson Timothy A. , Ash R. Bruce , Neumun Michael R. 
Published: May 2005

AbstractPotentiometric ion‐sensitive planar microelectrode arrays, and amperornetric enzyme‐containing biosensors were fabricated by photolithographic microelectronic technology on a flexible polyimide substrate. The steps of the microelectronics processing are summarized in more detail than previously described. The ion‐selective electrodes were tested in blood serum, whole blood, and in the hamstring muscle of anesthetized rabbits. The test and performance characteristics of planar pH are emphasized, and K+, Na+, and Ca2+ data are included in this review. New applied results are presented from experiments where the electrodes have been implanted into an in situ porcine beating heart at the midmyocardial depth in order to monitor H+ and K+ changes during the course of coronary artery occlusion.
Amperometric phenol sensor with immobilized bacteria
Authors: Orupõld Kaja , Mashirin Aleksei , Tenno Toomas 
Published: May 2005

AbstractAn amperometric phenol sensor, wherePseudomonus putidabacteria were immobilized on an amperometric oxygen sensor is described. Theoretical considerations of the steady‐state concentration distribution of oxygen and substrate in diffusion‐controlled microbial sensors are given. Validation of the theory was evaluated by comparing the experimental and theoretical data.
Use of polymer films in amperometric biosensors
Authors: Emr Sally A. , Yacynych Alexander M. 
Published: May 2005

AbstractDifferent types of polymeric films implemented in various capacities in amperometric biosensor design are reviewed. Conducting and nonconductinzg polymer films and composite films are considered. Methods of film fabrication such as solvent casting, electropolymerization, and adsorption are presented. Film function, including prevention of interference and fouling problems, immobilization of the enzyme or active biocomponent, extension of linear range, or to address biocompatibility problems are described. The use of polymeric films as a medium to incorporate mediators, while an important function, is too vast for review here. The applications of polymer film‐modified biosensors for selected analytical determinations are also presented. This review focuses upon the use of polymer films in amperometric biosensors and emphasizes innovative biosensor designs and unique applications, and omits traditional free‐standing films unless they are coupled with new types of polymer films or used innovatively.
Factors affecting the resistance and performance of fluoride ion‐selective electrodes
Authors: Shen Wei , Wang Xue D. , Cattrall Robert W. , Nyberg Graeme L. , Liesegang John 
Published: May 2005

AbstractSome lanthanide fluoride (LnF3, Ln = Ce, Nd, Sm) crystals have been grown, and fluoride ion‐selective electrodes (F‐ISE) have been constructed using these and some commercial LaF3, single crystal membranes. Aspects of crystal growing, particularly the high‐temperature dimorphism of SmF3, are addressed, and the effects on the electrode resistance and response characteristics of crystal quality, doping and membrane geometric dimensions are studied. The results show that, while doping is effective in increasing the membrane conductivity, membrane geometric dimensions also affect the electrical resistance substantially. Undoped membranes have noise‐free Nernstian response to F− solutions, provided appropriate geometric dimensions are chosen. The crystal orientation of the membrane does not have noticeable effect on the performance. The crystal quality also affects the membrane resistance and performance. Single crystal membranes with minor and localized visual defects show little difference in conductivity and no difference in performance compared with a ‘perfect’ single crystal membrane. Membranes grown from lower grade starting materials do not show poorer performance although these membranes were slightly cloudy. Membranes with severe visual defects have much lower conductivity, and deteriorated performance.
Redox polymers for electrocatalytic oxidation of NADH – A random block methyl‐siloxane polymer containing meldola blue
Authors: Persson Björn , Lee Hung Sui , Gorton Lo , Skotheim Terje , Bartlett Philip 
Published: May 2005

AbstractA water‐insoluble modified methyl‐siloxane polymer which held 9‐dimethylaminobenzo[a]phenoxazine‐7‐ium (Meldola Blue) units, was synthesized, characterized, and used to drop‐coat solid graphite electrodes. The electrocatalytic oxidation of the nicotinamide adenine dinucleotide (NADH) in the polymer could be described by the Michaelis–Menten type of kinetics as seen from steady‐state measurements in 0.25 M phosphate buffer, pH7, at 0 mV (vs. SCE). The electrocatalytic properties of the redox polymer was evaluated using the film thickness as a major variable. The theoretical model found to describe the NADH oxidation at the redox polymer modified electrode, is presented. A maximum NADH sensitivity of 40 μA cm−2 mM−1 at a coverage of 0.5 μg cm−2 was indicated.
Performance of platinum‐based spherical mercury microelectrodes in cyclic voltammetry and stripping analysis
Authors: Baldo M. Antonietta , Daniele Salvatore , Corbetta Massimo , Mazzocchin Gian A. 
Published: May 2005

AbstractThe performance of spherically shaped mercury microelectrodes, formed by electroreduction of mercury onto an inlaid platinum microdisk of radius r, characterized by different deposit heights, h, have been investigated for cyclic (CV) and anodic stripping (ASV) voltammetry. Electrodes with h/r ratio in the range 0.1–2 have been tested in solutions containing Pb2+ and Cd2+ in NaCl and NaClO4 + HClO4 as supporting electrolytes. For cyclic vodtammetry the results obtained indicated that the width at half height (w1/2), the peak current (ip) and the charge of the anodic stripping peak (Qs) depend on the h/r parameter. Particular attention has been devoted to the relation between the charge of the cathodic process and the anodic charge of the stripping peaks. It has been found that the experimental charge values involved in the cathodic and anodic scan agree within 3%, irrespective of the mercury thickness, indicating a complete stripping of the metals deposited in the mercury. For ASV the Pt‐Cd intermetallic compounds have been found to influence the stripping peak of cadmium for electrodes with h/r ≤ 1 and for concentrations of Cd2+ lower than 10−6 M. By exploiting the known properties of the mercury microelectrodes in stripping analysis, an absolute method, based on the charge associated with the stripping peak, has been applied for determining the labile fraction of the above cations in a pore‐water sample of the Venice lagoon.
A study of the hydroxide ion interference on several fluoride ion‐selective electrode membranes
Authors: Wang Xue D. , Shen Wei , Cattrall Robert W. , Nyberg Graeme L. , Liesegang John 
Published: May 2005

AbstractA study of the response characteristics of some fluoride selective electrodes based on three lanthanide fluoride single crystal membranes (LnF3; Ln = La, Ce and Nd) is reported. There is little difference between the response of these three membranes in buffered fluoride solutions except that CeF3 shows a slightly faster response and a slightly lower detection limit. The effect of the hydroxide ion on the response to fluoride is examined and is shown to be particularly severe for the CeF3 membrane. It is demonstrated that hydroxide ion interference on these membranes is due to the formation of hydroxo‐complexes which form within a gel layer at the membrane surface. A mechanism is proposed for the response of the electrodes to the hydroxide ion.