bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple iteration algorithm for PLS regression
Authors: Zhu Eryi , Barnes Ramon M.
Published: May 2005

A simple iteration algorithm that is faster and less memory‐intensive than the NIPALS iteration algorithm for PLS regression is presented. The iteration algorithm is obtained by treating the orthogonal expansion or decomposition of a matrix X as an extremum problem subject to normalization and orthogonality constraint conditions and then solving the problem by use of the method of Lagrange multipliers. The main idea in this method is to find the transformation vector r. The latent variable t is expressed exactly as the linear combination of X‐variables with the vector r so that the final regression coefficients can be conveniently provided. In the algorithm the recursion of the orthogonal projection is needed, which is derived by use of a matrix inverse formula. Algorithms are established from the equation for calculating the vector r that are suitable for dealing with three cases of large data sets. The first case is when the number of objects is very large, the number of variables is relatively small and the number of Y‐variables is equal to or greater than the number of X‐variables. The second case is when the number of objects is very large, the number of variables is relatively small and the number of X‐variables is greater than the number of Y‐variables. The last case is when the number of variables, either X‐ or Y‐variables, or both, is very large and the number of objects is small.
An extended strategy for exploratory multivariate image analysis including noise considerations
Authors: Pedersen F. , Bengtsson E. , Nordin B.
Published: May 2005

Multivariate image analysis (MIA) is a powerful tool for many image segmentation and classification problems, but the interpretation and understanding of the original and resulting multidimensional (multivariate) data are not always easy. A strategy for MIA has been proposed which describes its usage on multivariate images for segmentation tasks. MIA starts with principal component analysis (PCA) and then continues with interactive analysis of the output from PCA. In this paper a number of extensions to MIA are proposed. The extensions are the suggestion to incorporate preprocessing of the multivariate image in MIA, the suggestion to use synthetic multivariate image models which create a clear‐cut situation, and new visualization tools which improve the interactivity and understanding of the results. Extended MIA is applied on synthetic multivariate image data simulating a possible application with large noise, positron emission tomography (PET). As a result of the interactive analysis, suggestions for preprocessing emerge. The developed methodology for handling the noise is then applied on real PET image data with good results.
Application of regression analysis for motor gasoline classification
Authors: Khots M. S. , Nazarov V. I. , Emelyanov V. E.
Published: May 2005

A procedure for the classification of motor gasolines by their trend to carburettor icing has been proposed. For this goal a set of regression models was employed. Motor gasoline classification was carried out in terms of the isopropyl equivalent using seven physicochemical properties.
A PLS kernel algorithm for data sets with many variables and few objects. Part II: Cross‐validation, missing data and examples
Authors: Rännar Stefan , Geladi Paul , Lindgren Fredrik , Wold Svante
Published: May 2005

This is Part II of a series concerning the PLS kernel algorithm for data sets with many variables and few objects. Here the issues of cross‐validation and missing data are investigated. Both partial and full crossvalidation are evaluated in terms of predictive residuals and speed and are illustrated on real examples. Two related approaches to the solution of the missing data problem are presented. One is a full EM algorithm and the second a reduced EM algorithm which applies when the number of missing values is small. The two examples are multivariate calibration data sets. The first set consists of UV–visible data measured on mixtures of four metal ions. The second example consists of FT‐IR measurements on mixtures consisting of four different organic substances.
Incorporating auxiliary predictor variation in principal component regression models
Authors: Thomas Edward V.
Published: May 2005

In analytical chemistry a single fitted calibration model is used repeatedly to predict the level of the analyte of interest for the specimens comprising the prediction set. Unlike the calibration (or training) set, which is often limited in size, the prediction set can be very large.

In the case of multivariate calibration a number of methods such as PLS and PCR are commonly used to construct the calibration model. The set of instrumental measurements and the reference analyte level are available for each specimen in the calibration set. For specimens in the prediction set, only the instrumental measurements are available, since the problem is to predict the analyte level for these specimens. It is not widely recognized that predictions of the analyte levels for individual specimens can be improved by utilizing seemingly unrelated information from the instrumental measurements associated with the other members of the prediction set. In the case of PCR there exists a very straightforward procedure for doing this. A description of the various sources of prediction errors is provided to explain the ability of PCR to utilize this additional information. The use of PCR in this context is illustrated with both a synthetic and a real example.
On the structure of PLS in orthogonal designs
Authors: Langsrud Øyvind , Næs Tormod
Published: May 2005

This paper presents an interpretation of PLS applied to orthogonal explanatory variables. In particular, it is shown that in fractional factorial multiresponse experiments PLS2 gives identical results to ordinary least squares applied to principal components of the response variables. The general relationship is that the reduced‐rank regression algorithm which first projectsYonto theX‐space and then truncates this matrix by principal component analysis before performing ordinary least squares estimation gives the same predictor as PLS2 and SIMPLS if all the non‐zero eigenvalues ofXTXare identical.
Iteratively reweighted partial least squares: A performance analysis by monte carlo simulation
Authors: Cummins David J. , Andrews C. Webster
Published: May 2005

A robust implementation of partial least squares (PLS) is developed in which the method of iteratively reweighted least squares is adapted for use with PLS. The result is a PLS algorithm which is robust to outliers and is easy to implement. Examples and case studies are presented, followed by two Monte Carlo studies designed to explore the behavior of the method.

The paper begins with the motivation and intended applications for the procedure. A discussion is given of the method of interatively reweighted least squares (IRLS) for outlier detection. The procedure, given the name IRPLS, is then presented. Three case studies illustrate how the procedure works on various types of data and how it should be used. The first Monte Carlo study is designed to determine whether the IRPLS procedure correctly identifies multiple outliers in a wide variety of configurations. The second Monte Carlo study is designed to estimate the breakdown bound of the procedure.
Atmospheric pressure chemical vapor deposition of SiO2‐TiO2 antireflective films from [tri‐(tert‐butoxy)siloxy‐tri‐(tert‐butoxy)]titanium, [tC4H9O]3Si‐O‐Ti[OtC4H9]3, which is a single source alkoxide precursor
Authors: Narula Chaitanya K. , Varshney Ashima , Riaz Umar
Published: May 2005

Antireflective SiO2‐TiO2 films have potential applications in the automotive industry provided an economical method can be found to produce high‐quality films on a large scale. Following the discovery that alkoxides MOM' can be suitable single‐source precursors for the deposition of multicomponent oxides, the preparation of tC4H9O[3SiOTiOtC4H9]4 is described along with its application as a single‐source precursor for the deposition of SiO2 and TiO2 films via atmospheric‐pressure CVD.
Metal Chalcogenide Materials: Chalcogenolato complexes as “single‐source” precursors
Authors: Bochmann Manfred
Published: May 2005

Modern inorganic materials are required to fulfill a range of demandsfor quality and performance in an increasing number of applications. Single‐source precursor molecules can satisfy many of these requirements. In this review article ligand design (leading, for example, to the dimer shown in the Figure) to address problems associated with gas phase pre‐reactions, thermal stability, ease of handling, toxicity, and purity for II‐VI deposition are discussed.

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Synthesis and characterization of polyether adducts of group 2 metal thioacetates: Single‐source precursors to binary metal sulfide films, MS, where M  Ca, Sr, Ba
Authors: Kunze Klaus , Bihry Laurent , Atanasova Paolina , Hampden‐Smith Mark J. , Duesler Eileen N.
Published: May 2005

New polyether adducts of group 2 thioacetate complexes for the formation of binary metal sulfides are described. The synthesis and characterization of such precursors and their thermal reactivity to form the corresponding binary metal sulfides are briefly reported here. It is also shown that they can be used as single‐source precursors for aerosol‐assisted CVD, as illustrated by the deposition of CaS from Ca(SOCMe)2 · 15‐crown‐5.
Low‐temperature chemical vapor deposition of indium sulfide thin films using a novel single‐source indium thiocarboxylate compound as precursor
Authors: Shang Guihua , Kunze Klaus , Hampden‐Smith Mark J. , Duesler Eileen N.
Published: May 2005

The optoelectronic properties of gallium and indium chalcogenides have attracted considerable attention in recent years. This paper describes the synthesis and characterization of the first monomeric indium thiocarboxylate CVD precursor, with the molecular structure shown in the Figure. This compound has been successfully used to grow high purity, uniform, crystalline β‐In2S3 by aerosol‐assisted CVD at the lowest temperature (210°C) yet reported.

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Low temperature deposition of AIN films by an alternate supply of trimethyl aluminum and ammonia
Authors: Riihelä Diana , Ritala Mikko , Matero Raija , Leskelä Markku , Jokinen Janne , Haussalo Pekka
Published: May 2005

AIN thin films were grown by an alternate supply of trimethyl aluminum (TMA) and ammonia, i.e., according to the processing scheme of the atomic layer epitaxy (ALE) technique. In contrast with the ideal ALE process, no saturation of the growth rate was observed with increasing TMA pulse time. In addition, with fixed pulse times the growth rate was strongly temperature dependent. These observations were interpreted in terms of a self‐decomposition of TMA. Despite the absence of self‐limitation, the films were uniform and showed good structural quality. The deposition temperatures were remarkably low, 325–425°C, compared with CVD processes employing the same precursors. Time‐of‐flight elastic recoil detection analysis (TOF‐ERDA) and nuclear resonance broadening (NRB) measurements indicated that the films contained hydrogen, carbon, and oxygen impurities.
High temperature superconductors and related topics
Authors: Marks Tobin J. , Hitchman Michael L.
Published: May 2005

MOCVD offers many potential attractions for high temperature superconductor (HTS) film formation and device fabrication. In June 1996 the Third International Workshop on MOCVD of High Temperature Superconductors and Related topics was held in Strasbourg, France, within the E‐MRS Spring Meeting. The sessions of the Workshop are briefly described, including very short reports of the lectures, and a list of the titles of posters is given. The conclusions and recommendations of the panel discussion are summarized.
First liquid precursors for the CVD of palladium films
Authors: Zhang Yiping , Puddephatt Richard J.
Published: May 2005

Communication: There is much interest in the CVD of Pd films, which have a range of major applications. For Pd CVD, liquid precursors have many practical advantages and this paper reports the results of a systematic search for such precursors. Two have been found with the structure shown in the Figure, R1, R2, and R3 being either H or Me and R′ = tBu AND r″ = C3F7 in both cases.

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A Study of Stress in Microwave Plasma Chemical Vapor Deposited Diamond Films Using X‐Ray Diffraction
Authors: Haque M. Shahidul , Naseem Hameed A. , Malshe Ajay P. , Brown William D.
Published: May 2005

Residual stress in polycrystalline diamond films has been studied. Uniform polycrystalline diamond films were deposited on 3.0 in. diameter silicon substrates in a microwave plasma chemical vapor deposition (MPCVD) system. The effects of CH4/H2 ratio, pressure, and power variation on film stress were investigated. The macro‐stress, or uniform stress, in the films was measured using the X‐ray diffraction (XRD) d‐sin2ψ technique. In general, 〈220〉‐oriented films exhibited tensile stress and 〈111〉‐oriented films were in compression. The micro‐stress, or non‐uniform stress, calculated from diffraction peak broadening, was observed to be tensile for all samples. Films of relatively small grain size and 〈220〉 orientation showed both the highest micro‐stress and the highest macro‐stress. Film morphology was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), while the film texture was studied using XRD. Significant non‐diamond carbon was incorporated in 〈220〉‐oriented diamond as estimated from the intensity of the broad 1580 cm−1 peak in the Raman spectra. Much less non‐diamond carbon was detected in 〈111〉‐oriented diamond films. Good correlation between film morphology and measured stress was observed.
Plasma Polymer Films for Dropwise Condensation of Steam
Authors: Bonnar Mark P. , Burnside Bryce M. , Little Alan , Reuben Robert L. , Wilson John I. B.
Published: May 2005

Thin hydrophobic polymer films produced by radio frequency (rf) plasma decomposition of hexamethyldisiloxane (HMDSO) have been produced on flat metal (titanium, stainless steel, and copper/nickel) and silicon substrates. By using a statistical design methodology, the deposition conditions have been assessed for their control of the deposition rate, refractive index, water droplet contact angle, and longevity of dropwise condensation of steam. The films showing the best performance were those deposited at the slower rates, using low rf power density and high monomer flow rates, and having the lower refractive indices. There is some dependence on substrate material, with CuNi behaving worst, and titanium providing the best results of the three metals studied. This may be connected with the stability of an interfacial oxide layer. The steam immersion tests have already exceeded 7500 hours of continuous condensation, and many of the films are still producing excellent dropwise condensation. The reasons for these effects of preparation conditions and substrate material on performance are discussed with reference to the plasma chemical process.
Ion‐Beam‐Induced CVD: An Alternative Method of Thin Film Preparation
Authors: Espinós Juan P. , Fernádez Asunción , Caballero Alfonso , Jiménez Victor M. , Sánchez‐López Juan C. , Contreras Leopoldo , Leinen Dietmar , González‐Elipe Agustin R.
Published: May 2005

The ion‐beam‐induced chemical vapor deposition method for the preparation of thin films consists of the bombardment of a suitable substrate with O or N ions of relatively high energy while a flow of an organometallic precursor is directed onto its surface. Single and mixed oxides and nitride thin films can be prepared by this procedure. This paper describes the principles of the method, and presents some examples of thin films prepared with it (TiO2, PbTiO3, AlxTiyOz, AlN, and SnO2). Some characterization results of these thin films by different techniques are reported, with special emphasis on physical and electronic methods such as X‐ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and X‐ray absorption spectroscopy (XAS). Other aspects, such as the preferential removal of C, H, and other impurity atoms from the precursors under the action of oxygen beams, or the possibility of performing lithographic depositions of these dielectric materials, are also considered.
Electrocatalysis and flow detection of alcohols at ruthenium dioxide‐modified electrodes
Authors: Leech Donal , Wang Joseph , Smyth Malcolm R.
Published: May 2005

Ruthenium dioxide‐(RuO2)‐containing carbon paste electrodes exhibiting electrocatalytic responses toward alcohols are described. The electrocatalytic behavior is exploited for developing a highly stable and sensitive flow‐detection scheme for simple alcohols with a constant‐potential operation (+0.4 V vs. Ag/AgCl). The optimization of the system with respect to variables such as pH, flow rate, operating potential, and RuO2–surface “loading” is reported. The electrode response as stable over 2 weeks with a signal loss of 6%. Repeated injections (60) of methanol over a 120 minute period yielded a relative standard deviation of 3.4%. Detection limits for the various alcohols are dependent on the number and position of the hydroxyl groups, with limits ranging from 30 ng for glycerol to 3 μg for ethanol. Use of these electrodes in liquid chromatography with electrochemical detection is envisaged.
Biocoulometry of cholesterol using porous carbon felt electrodes
Authors: Uchiyama Shunichi , Kato Shinichi , Suzuki Shuichi , Hamamoto Osamu
Published: May 2005

Free and total cholesterols in human serum have been determined by controlled‐potential coulometry with porous carbon felt electrodes. In such a coulometric cell, a small amount of sample solution was dropped on the carbon felt dipped into electrolyte containing enzymes and a mediator. Hydrogen peroxide is produced by the enzymatic reaction of cholesterol catalyzed by cholesterol oxidase, and the complete electroreduction of hexacyanoferrate(III) ions [produced by the reaction of hexacynoferrate(II) ions and hydrogen peroxide catalyzed by peroxidase] was carried out under controlled‐potential conditions. In the case of determining total cholesterol in human serum, cholesterol esters were converted to free cholesterol by cholesterol esterase reaction prior to the addition of the sample solution into electrolyte. The conversion ratios of free cholesterol to hydrogen peroxide were found to be 85–89% (RSD < 6%). The electrolysis time of one sample was less than 5 minutes. Immobilization of cholesterol oxidase to the carbon felt surface was attempted; the activity of cholesterol oxidase, Immobilized by the diazo‐coupling method began to decrease 3 days after the immobilization.
Polarographic and voltammetric determination of sodium and tetramethylammonium mercaptoundecahydro‐closo‐dodecaborates
Authors: Jelen F. , Paleček E. , Štrouf O.
Published: May 2005

Sodium and tetramethylammonium mercaptoundecahydro‐closo‐dodecaborates (used in cancer therapy) produce sparingly soluble compounds with a mercury electrode. These compounds can be determined using differential pulse polarography at the dropping mercury electrode in the concentration range 1.5 × 10−5 to 5 × 10−7 M. Detection limit below 5 × 10−9 M can be attained with stripping voltammetry with relatively short accumulation times. Effects of various conditions are explored. The techniques are suitable for the analysis of pharmaceutical preparations containing mercaptoborate‐S.
Electrocatalytic amperometric detection at polymeric cobalt phthalocyanine electrodes
Authors: Qi Xiaohe , Baldwin Richard P. , Li Huawen , Guarr Thomas F.
Published: May 2005

Glassy carbon electrodes modified with a coating of a cobalt phthalocyanine containing polymer offer attractive features for applications as electrocatalytic amperometric sensors following liquid chromatography. These electrodes, which are formed by the anodic electropolymerization of Co‐4,4′,4″,4‴‐tetraaminophthalocyanine, exhibit electrocatalytic properties similar to those of earlier carbon paste electrodes containing Co phthalocyanine monomer added directly to the paste mixture. However, the polymer electrodes also offer increased stability and a compatibility with organic solvents not obtainable with the carbon paste version. The performance of the polymer electrodes is illustrated here for the detection of thiols following reversed‐phase liquid chromatography. Determination of picomole quantities of various thiols is possible at low positive potentials in mobile phases composed of 50% methanol or acetonitrile. Furthermore, the response of the electrodes is extremely stable, with more than 80% of the initial activity retained after 40 hours of continuous use.
Sodium activity measurements in protein solutions with sodium amalgam electrodes
Authors: Gunaratna P. C. , Marinenko G. , Koch W. F.
Published: May 2005

A method using sodium amalgam electrodes has been developed to study the effect of protein on activity measurements and residual liquid junction potential of sodium in protein‐containing solutions. It was tested for reliability by application to aqueous sodium chloride solutions before it was applied to protein‐containing solutions. The experimentally determined activity coefficients are in good agreement with the activity coefficients for aqueous sodium chloride solutions reported in literature. Therefore, we used this method to measure the activity of NaCl solutions containing varying concentrations of bovine serum albumin (BSA). The electrode slope of the electrode responses in a protein‐containing medium does not differ from that of pure aqueous solutions. A functional relationship has been established between the concentration of protein and the percent bias in the measurements. Measurements of electromotive force made in protein‐containing solutions do not show any evidence of protein effect on liquid junction potential.
Voltammetric studies of copper(I) and copper(II) with monoamines at the ionic strength of seawater (0.70 M NaClO4)
Authors: dos Santos Margarida M. Correia , Gonçalves M. Lurdes Simões
Published: May 2005

The stabilization of copper(I) by some amines was analyzed by voltammetric methods at the ionic strength of seawater (I = 0.7 M NaClO4). The amines studied were ethylamine, diethylamine, triethylamine, ethanolamine, and 5‐aminopenthanol. Voltammetric methods were used because copper(I) can be produced electrochemically if the ligands in solution stabilize this oxidation state. Differential pulse polarography (DPP) and voltammetry with platinum rotating disk electrodes (RDE) were employed. Because some of the voltammograms were distorted as a result of adsorption problems, adsorption has been studied by ac polarography. For the experimental conditions of negligible adsorption, the stability constants of copper(II) and copper (1) complexes have been determined.
Effect of proteins on the response of anion‐selective electrodes based on vitamin B12 derivatives
Authors: Florido Antonio , Daunert Sylvia , Bachas Leonidas G.
Published: May 2005

The potentiometric response of several polymer membrane based ion‐selective electrodes prepared with hydrophobic vitamin B12 derivatives is described. The effect of different proteins on the properties of these electrodes is discussed. It is suggested that the observed changes in potential upon addition of proteins are due mainly to nonspecific interactions between the proteins and the polymer membrane. Reduction of the nonspecific binding effect is possible by using a polymer matrix that contains free hydroxyl groups. The observed results agree with a theoretical model, which predicts that the nonspecific binding effect is more evident when membranes loaded with relatively small amounts of ionophore are used. The implications of these observations for the development of biosensors are discussed.
Determination of gold using anion‐exchange‐based chemically modified electrodes
Authors: Riley Peter J. , Wallace Cordon G.
Published: May 2005

The determination of gold by the application of electrodes modified with anion exchangers is considered. Particular attention is paid to investigating the capability of these electrodes to determine gold(III) in the presence of copper(II). Electrodes modified with a film of poly(4‐vinyl‐pyridine) or either chemisorbed electrochemically generated were investigated. It was found that copper(II) caused little or no interference in chloride media. However, copper(II) cyanide complexes interfered with the determination of gold cyanide solutions.
Depolarization end point can glassy carbon electrodes: Microscale coulometry of thioglycollic acid
Authors: Jovanović Vladislava M. , Jovanović Momir S.
Published: May 2005

An externally unpolarized twin couple of glassy carbon electrodes, undergoing different pretreatments, and connected to nothing but a recorder, was engaged for simple and fast end‐point detection of electrometric titrations of thioglycollic acid. Microquantities of this substance were determined coulometrically either by its neutralization or by an oxidometric mechanism using the same pair of glassy carbon electrodes in the indicator circuit.
Electrode reactions of nitroxide radicals. IX. Anodic oxidations of 4‐hydroxyimino‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl and 4‐[(aminocarbonyl)‐hydrazone]‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl in water solutions
Authors: de Ilarduya Jose I. Martinez , Krzyczmonik Paweł , Scholl Henryk , Grabowski Grzegorz
Published: May 2005

Anodic reactions of two stable nitroxide radicals, 4‐hydroxyimino‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (1) and 4‐[(aminocarbonyl)‐hydrazone]‐2.2,6,6‐tetramethylpiperidine‐1‐oxyl (2) were studied in aqueous solutions over the pH range 5.33–8.04 using the cyclic voltammetry technique. They show one‐electron oxidation processes of reversible and quasi‐reversible natures, depending on scan rate conditions at pH 5.33. The diffusion coefficients, the observed standard rate constants (ks), and the oxidation potentials for the redox reaction nitroxyl radical ⇌ oxoammonium salt have been determined. A one‐electron transfer process, followed by an irreversible chemical reaction, is observed at pH ≥ 5.71, and the rates of this reaction at pH 5.71 and 6.71 are 0.11 and 0.080 s−1, respectively. Controlled‐potential electrolysis at 0.8 V (vs. SCE) confirms a one‐electron electrode reaction.
Analytical applications of conducting polymers
Authors: Ivaska Ari
Published: May 2005

An overview of the analytical applications of conducting polymers is given. Examples of methods based on the change in electrically conductivity of the polymer membrane, exchange of the doping anion, determination of metals by deposition and stripping, incorporation of neutral compounds in the polymer membrane, and the novel properties of a polymer surface are presented and discussed.
Amperometric response of electrodes with porous coating to Gaussian concentration profiles in flowing streams
Authors: Cassidy John , Breen William , Lyons Michael E. G.
Published: May 2005

A numerical simulation is performed to calculate the amperometric response for a porous coating on an electrode surface to a Gaussian concentration plug in a flowing stream. The amperometric response is considered as a function of the layer thickness, the diffusion coefficient of the analyte through the layer, and the width of the Gaussian concentration profile. We consider the effect of the first two parameters on the magnitude of the current response and the lag time, which is the time delay between the time at which the peak of the concentration profile reaches the outer edge of the porous layer and the time of the peak current response. However, although it is not possible to decouple the magnitudes of the layer thickness and the diffusion coefficients from experimental measurements, it is possible to determine one parameter if the other is known. The width of the amperometric response varies linearly with that of the incident Gaussian concentration profile.
An automatic system for the measurement of dropping mercury electrode impedances
Authors: Andreu Rafael , González‐Arjona Domingo , Domínguez Manual , Molero Miguel , Roldán Emilio
Published: May 2005

A fully automated setup for impedance measurements at the dropping mercury electrode (DME) is described. It is based on the Solartron 1250 frequency response analyzer, and it incorporates an infrared drop‐fall detector. Synchronization with the DME as well as calibration procedures are considered in some detail. Experiments on dummy and electrolytic cells, with and without electroactive species, were performed, and data are compared with earlier results on the same systems.
Preparation and characterization of band nanoelectrodes made of carbonized polyacrylonitrile films
Authors: Wang Joseph , Brennsteiner Albert , Sylwester Alan P. , Renschler Clifford L.
Published: May 2005

We describe the fabrication and characterization of new nanoband electrodes, based on ultrathin carbon films produced by carbonization of deposited polyacrylonitrile. Because of their controlled thickness (down to molecular dimensions) and high electrical conductivity, such electrodes show great promise for electroanalytical work. Sigmoidal voltammograms, characteristic of nonlinear diffusion, are obtained. Direct measurements in electrolyte‐free organic media are illustrated. Effects of band thickness, scan rate, solute and electrolyte concentrations, and other variables are explored. These films and other forms of carbon from polyacrylonitrile present opportunities for a wide range of electrode materials.
Electrochemical and spectroelectrochemical study of copper bleomycin complexes
Authors: Fultz Mary Lou , Durst Richard A.
Published: May 2005

The electrochemical behavior of the copper(II) complex of bleomycin, a glycopeptide antibiotic with antitumor activity, was investigated in several buffer systems using cyclic voltammetry, polarography, coulometry, and spectroelectrochemistry. The copper bleomycin complex exhibited irreversible one‐electron reduction on glassy carbon and mercury electrodes and was electroinactive on platinum, gold, and silver. After the initial reduction process on mercury, the appearance of the Cu(0)/(II) redox couple indicated dissociation of the complex and subsequent reduction of the Cu(I) to the metal. In the presence of excess bleomycin, the Cu(II) reoxidized from the mercury electrode is rapidly complexed and no copper reduction process is observed. On glassy carbon, however, the Cu(I) bleomycin complex is stable and does not undergo further reduction, as demonstrated by spectroelectrochemistry at a reticulated vitreous carbon optically transparent electrode. Consequently, as with many metallo‐organic redox processes, there appear to be several possible electrochemical pathways depending on the pH, the electrode materials, and the experimental time domain.
Determination of ionized and total calcium in white wine using a calcium ion‐selective electrode
Authors: Cardwell Terence J. , Cattrall Robert W. , Mrzljak Robert I. , Sweeney Therese , Robins Lisa M. , Scollary Geoffrey R.
Published: May 2005

The free, or ionized, calcium concentration in white wine was determined using a calcium ion‐selective electrode. Calibration was achieved using a standard curve constructed from calcium standards that matched each wine sample in pH, ionic strength, and ethanol concentration. A more rapid procedure for the determination of the calcium ion activity using aqueous standards was also studied. The effect of dilution on the ratio of free to bound calcium was examined. Using a dilution factor of 10, between 71 and 78% of the total calcium concentration can be sensed by the electrode, the proportion increasing to between 81 and 92% with a dilution factor of 100. The estimation of the total calcium concentration, based on the value obtained from the 10‐fold dilution, is proposed.
Electrochemical detection for capillary electrophoresis
Authors: Curry P. D. , Engstro‐Silverman C. E. , Ewing A. G.
Published: May 2005

Capillary electrophoresis and the use of electrochemically based detection schemes for capillary electrophoresis are reviewed. The three different electrochemical methods used in capillary electrophoresis include potentiometric, conductivity, and amperometric detection.
Fundamental studies on fast scan stripping voltammetry with a microelectrode
Authors: Nomura Satoshi , Nozaki Koichi , Okazaki Satoshi
Published: May 2005

Application of rapid‐response voltammetry to stripping analysis was carried out, and novel fast scan stripping voltammetry (FSSV) was developed. A remarkable increase in analytical sensitivity could be attained as a result of the minimization of the background current through the use of an ultramicrodisk electrode (UMDE) and the fast scan rate of 300 V/s. The interference of dissolved oxygen and copper ion were greatly eliminated owing to their slow charge transfer rate. This new type of stripping method also turned out to be a rapid and reliable analytical method.
Relationship between charge transfer resistance and exchange current density of ion transfer at the interface of two immiscible electrolyte solutions
Authors: Horvai G.
Published: May 2005

A simple derivation shows the validity of the reciprocal relation between charge transfer resistance and exchange current density. The result is independent of the equation used for estimating the potential difference across the space charge region. Butler‐Volmer kinetics with Frumkin correction or the Ver wey‐Niessen model (i.e. Frumkin correction only) lead to the same result.
Voltammetric studies of nitrofuroxime
Authors: Reddy C. Suresh , Reddy S. Jayarama
Published: May 2005

The electrochemical reduction behavior of nitrofuroxime has been studied using do polarography, cyclic voltammetry, ac polarography, differential pulse polarography, millicoulometry, and controlled potential electrolysis in universal buffers of pH values ranging from 2.0 to 12.0 in DMF/water mixtures. Kinetic parameters such as diffusion coefficient and forward rate constant values are evaluated, and a reduction mechanism is proposed. A differential pulse polarography method is developed for the quantitative determination of nitrofuroxime in pharmaceutical formulations. The method of standard additions is used. The relative standard deviation and correlation coefficient are 1.84% and 0.991, respectively.
Application of ion‐selective electrodes in clinical analysis
Authors: Lewenstam Andrzej , Maj‐Zurawska Magdalena , Hulanicki Adam
Published: May 2005

Ion‐selective electrodes (ISEs) currently used in clinical analysis are reviewed. The theory of these sensors is outlined. Problems specific for the application of ISEs in clinical analysis are discussed. The prospects for use of new ISEs for clinical purposes are evaluated. More than 50 references are included.
Effect of background charge on estimating diffusion coefficients by chronocoulometry at glassy carbon electrodes
Authors: Sucheta Artur , Rusling James F.
Published: May 2005

Large background charges were observed in single potential‐step chronocoulometry obtained with glassy carbon electrodes. Analyses of uncorrected data gave large errors in diffusion coefficients (D) for vitamin B12 and ferrocyanide, whose electrode reactions are on opposite sides of 0 V (vs. SCE) where different surface redox processes occur. Subtraction of separately measured average background charge yielded values for D in good agreement with those previously reported. The use of the correct model for the electrode reaction was also necessary for accurate estimation of D. Even when the final potential was 350 mV positive of the quasireversible ferrocyanide cyclic voltammetric (CV) oxidation peak, the diffusion model gave poor fits to background subtracted chronocoulometric data and errors in D. This is attributed to formation of films on the electrodes at these potentials, especially at pH 12. However, the slow electron transfer model fit these data quite well, provided an accurate value of D, and also gave rate constants for heterogeneous electron transfer.
Reagentless hydrogen peroxide and glucose sensors based on peroxidase immobilized on graphite electrodes
Authors: Jönsson‐Pettersson Gunilla
Published: May 2005

The electrocatalytic reduction of hydrogen peroxide (H2O2) by horseradish peroxidase (HRP) immobilized on graphite electrodes without the addition of an electron mediator was found to start at + 600 mV vs. Ag/AgCl and the highest current was obtained at about −100 mV. With an applied potential of −50 mV and in the absence of soluble mediator, linear calibration curves for H2O2 were obtained between 0.5 μM and 250 μM and for β‐D‐glucose in air‐saturated solution between 2 μM and 0.5 μM (HRP co‐immobilized with glucose oxidase). Cross‐linking the enzymes with glutaraldehyde and bovine serum albumin was found to increase the stability of the sensors without causing mass transfer resistance within the enzyme layer. The response time was 5 seconds both for H2O2 and for glucose and the sample through put was 150 samples h−1. The glucose measurements were made in 0.1 M phosphate buffer, pH 6, where no interfering from physiological levels of ascorbic acid, uric acid, or paracetamol (acetaminophen) could be detected.
A novel and highly sensitive single‐sweep oscillopolarographic method for the determination of ultratrace amounts of ruthenium
Authors: Zhi‐liang Jiang
Published: May 2005

A novel and highly sensitive oscillopolarographic method is described for determining ruthenium as low as 7.9 × 10−11 M, based on its catalysis of the redox reaction between Ce(IV) and As(III). The changes in concentration of As(III) in the reaction is traced by single‐sweep oscillopolarography. The influence of 34 foreign ions is considered. Ruthenium in ore samples was analyzed by the method, and good results were obtained.
Voltammetry of captopril on the hanging mercury drop electrode
Authors: Passamonti Paolo , Ferraro Stefano , Bartocci Vito , Pucciarelli Filippo
Published: May 2005

The electrochemical behavior of 1‐[(2S)‐3‐mercapto‐2‐methyl‐1‐oxopropyl]‐L‐Proline (Captopril) was studied by cyclic voltammetry (CV). The influence of pH on the diffusion waves and the parameters associated with them were studied. The diffusion waves exhibit a quasi‐reversible mechanism at low pH (under pH = 6.5) and an irreversible electron transfer at higher pH values. Product adsorption waves (prepeaks) showing marked reversible behavior were observed and studied only at a pH of 2.20. Various parameters such as electron transfer rate (Ksh), maximum surface excess concentration (Γt), electron transfer coefficient (α), Frumkin's interaction parameter, (g) and diffusion coefficient (Dr) were calculated.
Electroanalysis with electrodes modified by inorganic films
Authors: Cox James A. , Jaworski Robert , Kulesza Pawel J.
Published: May 2005

The electroanalytical utility of electrodes modified with inorganic films is reviewed. Various types of inorganic layers (metal oxides, polynuclear transition metal cyanides, zeolites, metal porphyrins and phthalocyanines) are assessed. Various detection schemes based on these modified surfaces are described in 129 references.
The use of electropolymerization to produce new sensing surfaces: A review emphasizing electrode position of heteroaromatic compounds
Authors: Imisides Mark D. , John Richard , Riley Peter J. , Wallace Gordon G.
Published: May 2005

The synthesis and utilization of electrodes modified with conducting polymers is reviewed. Specific issues evaluated include the various approaches available to produce the required functionality at the electrode surface and the practical considerations to be addressed during synthesis, both in terms of hardware requirements and the chemistry of electropolymerization. The review concludes with a survey of the many applications of polymer‐modified electrodes and includes 112 references.
Potentiometric anion selectivities of polymer membranes doped with indium(III)‐porphyrins
Authors: Park S. B. , Matuszewski W. , Meyerhoff M. E. , Liu Y. H. , Kadish K. M.
Published: May 2005

The potentiometric anion responses of polymeric membranes doped with various indium (III)‐porphyrin structures are examined. The appropriate membranes are prepared by incorporating 1.0 wt % of the In(III)‐porphyrins in plasticized poly(vinyl chloride) films. When such membranes are incorporated within standard ion selective electrode bodies, the resulting electrodes display non‐Hofmeister anion selectivity, with a particularly enhanced and super‐Nernstian response to chloride. Among those porphyrins investigated, membranes doped with chloro(octaethylporphyrinato)indium(III) yield the largest and most reproducible potentiometric anion responses. These same membrane electrodes exhibit negligible response to protons (or hydroxide) in the range of pH 4.5–9.0. When utilized as a flow‐injection detector in conjunction with a protein diluent/buffer stream, the In(III)‐porphyrin based electrodes may be used to determine chloride levels in human serum samples.
The determination of electron transfer parameters for monosubstituted ferrocenes suitable as mediators in amperometric biosensors
Authors: Löffler Uwe , Göpel Wolfgang , Speiser Bernd
Published: May 2005

The quasi‐reversible electron transfer of monosubstituted ferrocenes at a gold electrode in acetonitrile, water, and an aqueous surfactant solution is characterized by formal potentials, diffusion coefficients, heterogeneous electron transfer rate constants, and transfer coefficients. These system parameters are calculated from peak potentials, peak currents, and peak potential differences by means of the multiparameter estimation technique. The results are compared with those of a combined evaluation of rotating disk electrode (rde) and cyclic voltammetric data. The former method can be used even if the rde results are distorted by filming of the electrode. The size of the molecules and, in the case of surfactant addition, the size of micelles containing the ferrocenes is estimated from diffusion coefficients. The electrochemical properties are discussed in view of future applications of these compounds as mediators in amperometric biosensors.
The application of quaternary ammonium ionic polymers to electroanalysis: Part 1. quaternary ammonium ionic polymer membranes for solid‐state, ion‐selective electrodes
Authors: Rocheleau Marie‐Josée , Purdy William C.
Published: May 2005

The preparation, properties, and response characteristics of polymeric ion‐selective membrane electrodes prepared from poly(vinylbenzyl chloride) functionalized with quaternary ammonium groups are described. Notably, a carbon‐support electrode coated with a film of poly(trihexylvinylbenzylammonium thiocyanate) yielded a highly selective Nernstian response to thiocyanate in the concentration range 5 × 10−5−0.1 M. The selectivity of this membrane electrode can be favorably compared with that of conventional thiocyanate ion‐selective electrodes. The use of functionalized polymer membranes with solid‐support electrodes represents an interesting alternative to conventional polymeric membranes.
The application of quaternary ammonium ionic polymers to electroanalysis: Part 2. Voltammetric studies with quaternary ammonium functionalized polymer film‐coated electrodes
Authors: Rocheleau Marie‐Josée , Purdy William C.
Published: May 2005

The application of quaternary ammonium functionalized polymers to voltammetric analysis is described. A glassy carbon electrode coated with a thin film of poly(trihexylvinylbenzylammonium chloride) exhibited attractive permselectivity to uric acid. Typically, this polymer‐modified electrode yielded a linear voltammetric response to uric acid in the concentration range of 1–10 μM. The ion exchange properties of poly(trihexylvinylbenzylammonium chloride) was related to the Gibbs‐Donnan equation. Also, chronoamperometry was used to probe the charge‐transport and response mechanisms within this type of ionic polymer film.
Adsorptive stripping tensammetry of commercially available oxyethylated alcohols: Part 2. Surfactants having C16C18hydrophobe
Authors: Szymanski Andrzej , Lukaszewski Zenon
Published: May 2005

The behavior of oxyethylated straight chain alcohols having the C16Cl8, hydrophobe and 10, 18, 25, 30, and 40 oxyethylene subunits was investigated, The dependences of the peak height on the concentration of surfactant, preconcentration time, and preconcentration potential were examined. Roughly, the behavior of the surfactants having 10–30 oxyethylene subunits can be described as the behavior of the system of two peaks: the dispersed one, which shifts toward a negative direction with the increase of concentration, and the narrow one, which has a stable position. The narrow peak is useful for analytical purposes whereas the dispersed one makes the background current worse. The surfactant having 40 oxyethylene subunits forms two narrow closely located peaks, useful for analysis. The peaks of all surfactants increase linearly with the increase of the number of oxyethylene subunits, under selected conditions.
Determination of copper in process manganese sulfate electrolyte by differential pulse anodic stripping voltammetry
Authors: Adeloju Samuel B. , Cui Chun‐Guo
Published: May 2005

A method is described for the reliable determination of copper in manganese sulfate electrolyte by the differential pulse anodic stripping voltammetry on a glassy carbon mercury film electrode (GCMFE). Unlike on the hanging mercury drop electrode, the high manganese sulfate electrolyte (1.3 M) proved to be an adequate medium when acidified with nitric acid for the determination of copper on a GCMFE. Under these conditions, the copper response was more pronounced due to the formation or either an intermetallic compound with manganese or a manganese oxide, which oxidizes during the stripping step. In contrast, the buffering of the electrolyte to pH ˜5 with an acetate buffer was inadequate for the copper determination. The use of the acetate buffer was also proved to be responsible for the irreproducible behavior of the copper response on mercury electrodes. Based on the preliminary acidification of the manganese sulfate electrolyte with nitric acid and the use of a 2 min deposition period, a linear concentration range between 0–100 μg/1 and a minimum detectable amount of 1 μg/1 copper above the background level present in the process plant electrolyte were accomplished. The precision of the method (relative standard deviation) ranges between 1 and 2%. Recovery studies indicated that the voltammetric method is capable of detecting 96–100% of the copper present in the high manganese sulfate electrolyte medium, providing that the sample is acidified initially with nitric acid.
An electrochemical capillary fill device for the analysis of glucose incorporating glucose oxidase and ruthenium (III) hexamine as mediator
Authors: Morris N. A. , Cardosi M. F. , Birch B. J. , Turner A. P. F.
Published: May 2005

This article describes a coulometric measurement device for glucose based on thin‐layer bulk electrolysis. The analysis is carried out in a specially constructed cell, the electrochemical capillary fill device, which has a total volume of less than 20μl. Once the sample enters the cell by capillary action, the freeze‐dried assay components (glucose oxidase, ruthenium (III) hexamine, buffer salts, etc.) become solubilized and quickly disperse throughout the volume of the cell. After a period of one min, the time taken for the enzyme catalyzed oxidation of glucose to gluconic acid to reach completion, a potential step is applied and the current transient, resulting from the oxidation of reduced mediator at the working electrode, integrated over a period of 60 s. From the resultant charge value, the concentration of glucose in the sample can be unambiguously determined. The response of the sensor is both linear and accurate over the range 2–30 mM, which covers the normally accepted range for blood glucose levels in diabetic patients. The second order rate constant for the reaction between reduced glucose oxidase and ruthenium (III) hexamine was evaluated by conducting a numerically based analysis that was designed to separate the diffusional and catatytic components of current transients.