bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the laser‐induced lens generated in guest‐host liquid crystals
Authors: Morisaki Takashi , Ono Hiroshi
Published: October 2004

We used the high‐efficiency nonlinear optical effect caused by the photothermal effect of guest‐host (dye‐doped) liquid crystals to form a laser‐induced concave lens by irradiation with a Gaussian beam. The process for forming the laser‐induced concave lens was identified by adapting diffraction theory to the pump‐probe method. We also considered the anisotropy of the thermal conductor in the liquid crystal layer and could explain the laser‐induced concave lens characteristics observed in practice including the dependence on the dye concentration and the effect of the thickness of the liquid crystal layer from the results of three‐dimensional heat conduction analysis. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(11): 10–19, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20085
Acquisition and organization of personal knowledge through WWW browsing
Authors: Takashiro Toru , Takeda Hideaki
Published: October 2004

The purpose of this paper is to construct a system to support the process whereby the user acquires knowledge by viewing electronic documents, including documents on the World Wide Web (WWW). The paper focuses on the structure of the individual knowledge and the context that forms its background, based on the experience, interests, and concerns of the individual user. A system called “MindHeap,” which models the structure of the individual knowledge in the system by interaction with the user, and presents the information to the user on the basis of that model, was previously implemented. The system has a function allowing interaction with the user in addition to the functions of an ordinary WWW browser. The user can input the part of the document that is of interest by tracing it on the screen. As a result of repeated input, the structure of the individual knowledge is automatically rearranged and systematized on the basis of the input and its context. Thus, the system supports the user with information in various formats. Evaluation experiments of the system are presented in this paper, demonstrating that the technique works effectively. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(11): 38–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20127
Construction of image processing procedures from a small number of learning samples using the IMPRESS vision expert system
Authors: Hamada Toshihiro , Shimizu Akinobu , Hasegawa Jun‐ichi , Toriwaki Jun‐ichiro
Published: October 2004

IMPRESS is an image processing expert system in which the objective of processing is presented in the form of a figure (called the sample figure), and the image processing procedure to extract the corresponding figure from the original image is automatically generated. The authors have already considered the case in which multiple pairs of the original image and the sample figure are input, and have developed a procedure consolidating function whereby a procedure that works effectively in common for all pairs is generated. However, when the procedure is consolidated from a small number of learning samples, there is a problem with the effectiveness of the procedure. Specifically, when the consolidated function is applied to the ensemble of samples, the performance is sometimes greatly degraded compared to that for the learning samples. Consequently, we propose the following method. The deviation of the average score for the learning samples from the average score for the ensemble is estimated in the probabilistic sense. Then, by specifying the range of procedure search, a procedure with high versatility is derived from a small number of samples. In this study, the method under consideration is applied to the problem of automatic procedure construction for a procedure for defect extraction from real LSI package surfaces. The effectiveness of the method is investigated by comparing the result to the conventional consolidation procedure. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(11): 49–62, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20128
An in situ Template Route for Fabricating Metal Chalcogenide Hollow Spherical Assemblies Sonochemically
Authors: Xu Shu , Wang Hui , Zhu Jun‐Jie , Xin Xin‐Quan , Chen Hong‐Yuan
Published: October 2004

An ultrasound‐assisted in situ template approach has been developed for fabricating a series of nanoscale metal chalcogenides in the form of well‐defined hollow spherical assemblies. These hollow spherical assemblies have well‐controlled dimensions and are composed of uniform nanoparticles. Initially, metal hydroxide particles self‐assemble into spherical templates generated in situ, and subsequent surface crystal growth leads to hollow spherical structures. Ultrasound irradiation plays a critical role both in the formation of the intermediate templates and in the crystal‐growth process. This approach provides a convenient and efficient one‐step pathway to the large‐scale fabrication of hollow spherical nanostructures. It also represents a new demonstration of sonochemical effects on the formation and assembly of crystalline particles on the nanometer scale. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Incorporation of Inorganic Anions in Calcite
Authors: Kontrec Jasminka , Kralj Damir , Brečević Ljerka , Falini Giuseppe , Fermani Simona , Noethig‐Laslo Vesna , Mirosavljević Krunoslav
Published: October 2004

A number of analytical methods and techniques (X‐ray diffraction, FT‐IR and electron paramagnetic resonance spectroscopy, ionic chromatography, scanning electron microscopy, etc.) have been used to study the mode and sites of incorporation of some common inorganic anions (SO42−, NO3− and Cl−) in the calcite crystal lattice. Calcite, the thermodynamically stable calcium carbonate polymorph under standard conditions, was prepared by spontaneous precipitation from calcium hydroxide and carbonic acid solutions. The particular co‐anion was added into the carbonic acid solution in the form of a calcium salt before mixing the reactants. The system prepared in such a way is particularly suitable for investigating the mode of foreign anion incorporation into the crystal lattice of calcite. Apart from the constituent ions and the products of water protolysis, this system contains only the co‐anion examined. In order to study the local environment in the calcite crystal lattice by EPR spectroscopy, Mn2+ was used as a paramagnetic substitute for Ca2+. The experiments were performed at 25 °C and the samples for analyses were taken after a predetermined ageing time of 20 min. It was found that the co‐anions, when added in the concentrations examined, did not affect the morphology of the calcite crystals but were incorporated into the calcite structure. The largest distortion of the calcite structure was obtained when sulfate ions were added. The measured parameters of the calcite unit cell are given, the results obtained are discussed and a model that explains the possible mode and sites of sulfate incorporation is presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Luminescent Zn and Cd Coordination Polymers
Authors: Jiang Chao , Yu Zhaopeng , Jiao Chao , Wang Sujing , Li Jiaming , Wang Zhiyong , Cui Yong
Published: October 2004

The hydrothermal reactions of Zn(ClO4)2·6H2O and Cd(ClO4)2·6H2O with 1,3‐bis(2H‐tetrazol‐5‐yl)benzene in an aqueous ethanol and an aqueous methanol/pyridine medium, respectively, yielded a 3D and a 2D metal‐organic coordination framework [Zn(1,3‐BTB)] (1) and [Cd(1,3‐BTB)2(Py)2(H2O)2] [Cd[Cd(Py)(H2O)]2(1,3‐BTB)2] (2) (1,3‐BTB = 1,3‐ditetrazolylbenzene, Py = pyridine), respectively. Species 1 possesses an open network structure with no guest molecules residing in its small cavities. The structural characterisation of 2 shows a 2D layered framework consisting of nano‐sized polytube structures which are stacked one on top of another in the (110) plane giving small channels along the b and c axes. Additionally, compounds 1 and 2 exhibit strong fluorescence at room temperature in the solid state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Facile [N]C−H Activation by a (P,N)‐Chelate [3]Ferrocenophane−Ruthenium System
Authors: Liptau Patrick , Carmona Daniel , Oro Luis A. , Lahoz Fernando J. , Kehr Gerald , Erker Gerhard
Published: October 2004

The chelate ligand 5 was prepared from the corresponding (dimethylamino)[3]ferrocenophane by directed ortho‐lithiation with n‐butyllithium followed by treatment with ClPPh2. The rigid (P,N)‐chelate ligand reacts with [Ru(η6‐p‐cymene)Cl2] dimer in the presence of KPF6 in methanol to afford two products in an almost equimolar ratio. Instead of the simple addition product of the [Ru(p‐cymene)Cl]+ cation reagent to the chelate, selective C−H abstraction at an N−CH3 moiety occurs with the formation of the “metallaaziridinium”‐type product 8 (isolated as its PF6− salt). The liberated equivalent of HCl is trapped by the putative (P,N)‐chelate [RuCl]+ complex intermediate to form the corresponding internal hydrochloride complex 7. The starting material 5 and the products 8 and 7 were characterised by single‐crystal X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Binucleating Aza‐Sulfonate and Aza‐Sulfinate Macrocycles — Synthesis and Coordination Chemistry
Authors: Hausmann Julia , Käss Steffen , Klod Sabrina , Kleinpeter Erich , Kersting Berthold
Published: October 2004

The preparation and ligating properties of S‐oxygenated derivatives of a macrobinucleating hexaazadithiophenolate macrocycle H2L1 of the Robson type towards nickel(II) and zinc(II) ions are reported. Nickel complexes of the hexaazadiphenylsulfonate ligand (L2)2− [(L2)NiII2(μ‐L)]+ (L = m‐Cl‐OBz− (3), Cl− (4) and OAc− (6)] are readily obtained in high yields by oxidation of the respective [(L1)NiII2(μ‐L)]+ parent complexes [L = m‐Cl‐OBz− (2), Cl− (1), OAc− (5)] with meta‐chloroperoxybenzoic acid or hydrogen peroxide. Decomposition of the sulfonate complexes gives the free macrocycle H2L2 which, upon treatment with Zn(OAc)2·2H2O, produces the diamagnetic zinc complex [(L2)ZnII2(OAc)]+ (8). A dinuclear CuII complex of the hexaazadisulfinate derivative (L3′)2−, [(L3)CuII2]2+ (9), is formed rather unexpectedly by air oxidation of (L1)2− in the presence of CuI. The crystal‐structure determinations of the perchlorate or tetraphenylborate salts of 2, 3, and 4 show that the new ligands support the formation of binuclear complexes with bowl‐shaped, calixarene‐like binding cavities. NMR spectroscopic studies of 8 show that the complexes retain their solid‐state structures in solution. A crystal‐structure determination of 9 reveals two five‐coordinate CuII ions bridged by the two sulfinate functions of (L3)2−. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of (Vinylidene)‐ and (Cyclopropenyl)ruthenium Complexes Containing a Tris(pyrazolyl)borato (Tp) Ligand
Authors: Lo Yih‐Hsing , Lin Ying‐Chih , Lee Gene‐Hsiang , Wang Yu
Published: October 2004

A convenient high‐yield route to [Ru(C≡C−Ph)(Tp)(PPh3)2] [2; Tp = HB(pz)3, pz = pyrazolyl] has been found through the intermediacy of [RuCl2(Hpz)2(PPh3)2] (1). This complex is readily obtained on treatment of [RuCl2(PPh3)3] with 2 equiv. of pyrazole in boiling THF. The molecular structures of complexes 1 and 2 have been confirmed by single‐crystal X‐ray diffraction analysis. A number of new cationic vinylidene complexes [Ru{=C=C(Ph)CH2R}(Tp)(PPh3)2]+ [3a, R = CN; 3b, R = HC=CH2; 3c, R = CH=C(CH3)2; 3d, R = Ph; 3e, R = C(O)OMe] have been prepared by electrophilic addition of organic halides to complex 2. The deprotonation reaction of 3a yields the cyclopropenyl complex 4a. One phosphane ligand of 4a is remarkably labile, being replaced by donor ligands L to yield diastereomeric mixtures of the cyclopropenyl complexes 5a−5d mostly in an approximate 4:1 ratio. The cyclopropenyl rings in 4a and 5a are susceptible to ring opening by I2. In addition, treatment of 4a with nBuNC in the presence of MeOH results in substitution of a phosphane ligand by nBuNC followed by protonation of the three‐membered ring by MeOH. This is then followed by addition of methoxide to give the vinyl ether complex [Ru{C(OMe)=C(Ph)CH2CN}(Tp)(PPh3)(nBuNC)] (8a). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of a Fluorescent Sulfatide for the Study of CD1 Antigen Binding Properties
Authors: Franchini Laura , Compostella Federica , Donda Alena , Mori Lucia , Colombo Diego , De Libero Gennaro , Matto Pamela , Ronchetti Fiamma , Panza Luigi
Published: October 2004

A fluorescent derivative of sulfatide, labeled with a dansyl probe at position 6 of galactose, was prepared through a glycosylation reaction between a 6‐O‐functionalized galactose donor and 3‐O‐benzoyl‐azidosphingosine. The sphingoid acceptor was obtained in high yield through exploitation of a highly stereoselective nucleophilic addition of pentadecyne to 2,3‐O‐cyclohexylidene‐D‐glyceraldehyde. The fluorescent sulfatide binds to soluble recombinant human CD1a and is a valuable tool for the study of CD1 antigen binding properties. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Adsorption and Reactivity of Chlorogenic Acid at a Hydrophobic Carbon Ceramic Composite Electrode: Application for the Amperometric Detection of Hydrazine
Authors: Salimi Abdollah , Hallaj Rahman
Published: October 2004

Sol‐gel technique was used for construction of a carbon composite electrode. The prepared carbon ceramic electrode was modified with electroless deposition of chlorogenic acid for less than 1 min. The adsorbed thin films of chlorogenic acid on carbon composite electrode show one pair of peaks with a surface confined characteristic, which strongly depends on the solution pH, as anticipated for quinone /hydroquinone functionalities. The modified electrode shows highly catalytic activity toward hydrazine electrooxidation at wide pH range (5–11). Also the rotating modified electrode shows excellent analytical performance for amperometric determination of hydrazine. The detection limit, sensitivity, response time and linear dynamic range are 20 nM, 220 nA / μM, 1 second and 0.1 μM‐1 mM, respectively. The catalytic rate constant for hydrazine oxidation at the surface of modified electrode was evaluated by cyclic voltammetry and was found to be around 1.5×103 M−1s−1in phosphate buffer solution (pH 8). The precision of chronoamperometric measurements was 1–3% for 5 replicate determinations in the concentration range of the linear calibration. The reproducibility of modified CCE was evaluated with 8 successive polishing and modifications and then the anodic peak current was measured (RSD 2%). The advantages of this sensor are excellent catalytic activity, high sensitivity, good reproducibility and simplicity of preparation at short time periods.
Renewable Surface Sol‐gel Derived Carbon Ceramic Electrode Modified with Copper Complex and Its Application as an Amperometric Sensor for Bromate Detection
Authors: Salimi Abdollah , Alizadeh Vali , Hadadzadeh Hasan
Published: October 2004

A sol‐gel technique was used for the preparation of a three dimensional carbon composite electrode modified with [Cu(bpy)2]Br2 complex. A reversible redox couple of Cu(II)/Cu(I) is observed at the electrode surface. The electrochemical behavior and stability of the modified electrode was characterized by cyclic voltammetry. The charge transfer coefficient (α) and charge transfer rate constant (Ks) for the modified electrode were determined by cyclic voltammetry, which were found to be 0.46 and 14.2 s−1, respectively. The modified electrode showed excellent catalytic activity toward bromate reduction at significantly reduced overpotentials and can be used successfully for amperometric detection of bromate. Under the optimized conditions, the calibration plots are linear in the concentration range 0.5 μM −200μM. Detection limit (signal to noise is 3) and sensitivity were found to be 0.1 μM and 20 nA / μM, respectively. These analytical parameters compare favorably with those obtained with modern analytical techniques. The modified carbon ceramic electrode doped with Cu‐Complex shows a good reproducibility, a short response time (t<2 s), remarkable long term stability (>4 months) and especially good surface renewability by simple mechanical polishing (RSD for 6 successive polishing is 1.5%).
Binding of Copper(II) to Pectins by Electrochemical Methods
Authors: Vilhena C. , Gonçalves M. L. , Mota A. M.
Published: October 2004

The interaction between Cu(II) and pectin extracted from citrus fruit was studied in KNO3 0.10 mol dm−3 at 25 °C and pH 5.5, using ion selective electrode potentiometry and voltammetry, namely differential pulse polarography and square‐wave voltammetry. Although many independent variables may affect Cu(II)‐polymer interactions such as charge density, polymer concentration and copper to polymer concentration ratio, a good fitting was observed for the model with ML and ML2 complex species, when M:L total concentration (mol dm−3) ratio varies from 0.2 to 2.7 and the ligand concentration is in the range (0.2 to 1) g dm−3, i.e., (0.4 to 2)×10−3 mol COO− dm−3. The complex parameters found in these conditions were log βCuL=3.5±0.1 and log βCuL2= 8.0±0.2. For lower total ligand and total metal ion concentrations, used in voltammetry, the interaction Cu(II)‐pectin is affected by a cooperative mode (increase of metal ion‐ligand affinity) when the total metal ion concentration increases and by an anti‐cooperative mode when the total ligand concentration increases, possibly due to different conformations of the polymer.
Enzymatic Biosensor Based on the ISFET and Photopolymeric Membrane for the Determinaion of Urea
Authors: Rebriiev A. V. , Starodub N. F.
Published: October 2004

An ISFET based enzymatic biosensor was developed for the determination of urea. Immobilization of urease was accomplished by the use of liquid mixture which contained vinylpyrrolidone, oligouretane metacrylate and oligocarbonate metacrylate and which can form a polymer under the influence of ultraviolet. The biosensor has the following characteristics: the linear field of responses is in the range of 0.05–20 mM, curve slope – 38 mV/pC, and response time 5–10 min. The increase of the temperature from 28 to 41 °C leads to 15% increase in the intensity of the response of the biosensor. The maximum response is observed at pH 6.0–6.5. At the increase of the NaCl concentration in solution up to 300 mM the biosensor response drops off and achieves half of its initial level. NH4Cl causes a stronger inhibition of enzyme activity comparing to NaCl. The results obtained with the developed biosensor correlate with the data of standard calorimetric methods. The intensity of the biosensor response decreases gradually during 40 days up to 80% of the initial level. The biosensors prepared with a fresh membrane or membrane preserved during 46 days at 2 °C gave similar responses in solution with an equal concentration of a substrate. It is concluded that the developed enzymatic biosensor is perspective for its clinical application for the determination of urea in blood and that the proposed method to prepare a selective biological membrane may be in a simple way included in integral technology of the semiconductor transducer manufacturing.
FET‐Based Biosensors for The Direct Detection of Organophosphate Neurotoxins
Authors: Simonian A. L. , Flounders A. W. , Wild J. R.
Published: October 2004

Recent world‐wide terrorist events associated with the threat of hazardous chemical agent proliferation, and outbreaks of chemical contamination in the food supply has demonstrated an urgent need for sensors that can directly detect the presence of dangerous chemical toxins. Such sensors must enable real‐time detection and accurate identification of different classes of pesticides (e.g., carbamates and organophosphates) but must especially discriminate between widely used organophosphate (OP) pesticides and G‐ and V‐type organophosphate chemical warfare nerve agents. Present field analytic sensors are bulky with limited specificity, require specially‐trained personnel, and, in some cases, depend upon lengthy analysis time and specialized facilities. Most bioanalytical based systems are biomimetic. These sensors utilize sensitive enzyme recognition elements that are the in‐vivo target of the neurotoxic agents which the sensor is attempting to detect. The strategy is well founded; if you want to detect cholinesterase toxins use cholinesterase receptors. However, this approach has multiple limitations. Cholinesterase receptors are sensitive to a wide range of non‐related compounds and require lengthy incubation time. Cholinesterase sensors are inherently inhibition mode and therefore require baseline testing followed by sample exposure, retest and comparison to baseline. Finally, due to the irreversible nature of enzyme‐ligand interactions, inhibition‐mode sensors cannot be reused without regeneration of enzyme activity, which in many cases is inefficient and time‐consuming. In 1996, we pioneered a new “kinetic” approach for the direct detection of OP neurotoxins based on agent hydrolysis by the enzyme organophosphate hydrolase (OPH; EC 3.1.8.2; phosphotriesterase) and further identified a novel multi‐enzyme strategy for discrimination between different classes of neurotoxins. The major advantage of this sensor strategy is it allows direct and continuous measurement of OP agents using a reversible biorecognition element. We also investigated incorporation of enzymes with variations in substrate specificity (e.g., native OPH, site‐directed mutants of OPH, and OPAA (EC 3.1.8.1), based upon preferential hydrolysis of PO, PF and PS bonds to enable discrimination among chemically diverse OP compounds. Organophosphate hydrolase enzymes were integrated with several different transduction platforms including conventional pH electrodes, fluoride ion‐sensitive electrodes, and pH‐responsive fluorescent dyes. Detection limit for most systems was in the low ppm concentration range. This article reviews our integration of organophosphate hydrolase enzymes with pH sensitive field effect transistors (FETs) for OP detection.
Purification of the Escherichia coli K5 capsular polysaccharide and use of high‐performance capillary electrophoresis to qualitative and quantitative monitor the process
Authors: Volpi Nicola
Published: October 2004

A rapid, highly sensitive, and reproducible high‐performance capillary electrophoresis (HPCE) method (electrokinetic chromatography with sodium dodecyl sulfate) is described for the determination of the polysaccharide from the uropathogenic Escherichia coli K5 bacteria Bi8337/41 010:K5:H4. This natural polysaccharide having the structure of a desulfo‐heparin composed of ‐4)‐αGlcUA‐(1,4)‐α‐GlcNAc‐(1‐ is separated (GlcUA = D‐glucuronic acid; GlcNAc = D‐glucosamine) and qualitatively and quantitatively determined within 20 min on an uncoated fused‐silica capillary using normal polarity at 20 kV and detection at 200 nm. A linear relationship (correlation coefficient > ∼0.99) was found for the polymer over a wide range of concentrations, from approx. 60 to 1500 ng, with a detection sensitivity of < ∼60 ng. Furthermore, this qualitative and quantitative HPCE approach was applied to the K5 extraction and purification process from cultured bacteria in several stages. HPCE was also able to separate several molecular species mainly due to the presence of polysaccharides of distinct and increasing mean chain lengths. A linear relationship was found for migration time and log molecular mass of different K5 polysaccharide species, and this model was used to calculate the molecular mass of the main K5 species producing a result of approx. 17 000, also confirmed by high‐performance size‐exclusion chromatography analysis, yielding approx. 17 200.
Continuous on‐line derivatization and selective separation of D‐aspartic acid by a capillary electrophoresis system with a continuous sample introduction interface
Authors: Fan Liuyin , Cheng Yuqiao , Chen Hongli , Liu Lihong , Chen Xingguo , Hu Zhide
Published: October 2004

A rapid and selective method is described for the separation of D‐aspartic acid (D‐Asp) using a continuous on‐line derivatization system coupled to capillary electrophoresis (CE). D‐Asp was derivatized using o‐phthaldialdehyde/N‐acetyl‐L‐cysteine (OPA/NAC). By on‐line derivatization, amino acid enantiomers were automatically and reproducibly converted to the UV‐absorbing diastereomer derivatives which were separated by capillary zone electrophoresis (CZE) in the presence of 10 mmol/L β‐cyclodextrin (β‐CD). Under the investigated separation conditions, D‐Asp is resolved from L‐aspartic acid (L‐Asp) and other amino acids in a standard mixture of amino acids. The separation could be achieved within 4 min and the sample throughput rate can reach up to 16 h‐1. The repeatability (defined as relative standard deviation, RSD) was 3.21%, 3.58% with peak area evaluation and 3.72%, 4.03% with peak height evaluation for L‐Asp and D‐Asp.
Analyses of preservatives by capillary electrochromatography using methacrylate ester‐based monolithic columns
Authors: Huang Hsi‐Ya , Chiu Chen‐Wen , Huang I‐Yun , Yeh Jui‐Ming
Published: October 2004

Five common food preservatives were analyzed by capillary electrochromatography, utilizing a methacrylate ester‐based monolithic capillary as separation column. In order to optimize the separation of these preservatives, the effects of the pore size of the polymeric stationary phase, the pH and composition of the mobile phase on separation were examined. For all analytes, it was found that an increase in pore size caused a reduction in retention time. However, separation performances were greatly improved in monolithic columns with smaller pore sizes. The pH of the mobile phase had little influence on separation resolution, but a dramatic effect on the amount of sample that was needed to be electrokinetically injected into the monolithic column. In addition, the retention behaviors of these analytes were strongly influenced by the level of acetonitrile in the mobile phase. An optimal separation of the five preservatives was obtained within 7.0 min with a pH 3.0 mobile phase composed of phosphate buffer and acetonitrile 35:65 v/v. Finally, preservatives in real commercial products, including cold syrup, lotion, wine, and soy sauces, were successfully determined by the methacrylate ester‐based polymeric monolithic column under this optimized condition.
Rapid determination of aliphatic amines in water samples by pressure‐assisted monolithic octadecylsilica capillary electrochromatography‐mass spectrometry
Authors: Santos Bricio , Simonet Bartolomé M. , Ríos Angel , Valcárcel Miguel
Published: October 2004

A pressure‐assisted capillary chromatography‐mass spectrometry method based on the use of a monolithic octadecylsilica (ODS) capillary is proposed for the determination of aliphatic amines. A 25 mM citric acid buffer containing 10% methanol is used as running electrolyte. Separation is achieved by simultaneously applying a capillary electrophoresis (CE) voltage of 13 kV and an overimposed pressure of 8 bar. The use of pressure is required to ensure stable electrospray conditions. Analysis times are reduced by using a capillary column consisting of a 30 cm long monolithic silica capillary column bound with ODS and a fused‐silica capillary column also 30 cm long. The proposed method was successfully applied to the determination of low‐molecular‐weight aliphatic amines in tap and river water. The analysis of real samples requires cleanup and preconcentration, which can be performed automatically by inserting a minicolumn in the replenishment system of the commercial instrument.
Eigenmobilities in background electrolytes for capillary zone electrophoresis: III. Linear theory of electromigration
Authors: Štědrý Milan , Jaroš Michal , Hruška Vlastimil , Gaš Bohuslav
Published: October 2004

A mathematical model of capillary zone electrophoresis (CZE) based on the conception of eigenmobilities, which are the eigenvalues of a matrix M tied to the linearized governing equations is presented. The model considers CZE systems, where constituents, either analytes or components of the background electrolyte (BGE), are weak electrolytes – acids, bases, or ampholytes. There is no restriction on the number of components nor on the valence of the constituents nor on pH of the BGE. An electrophoretic system with N constituents has N eigenmobilities. In most BGEs one or two eigenmobilities are very close to zero so their corresponding eigenzones move very slowly. However, there are BGEs where no eigenmobility is close to zero. The mathematical model further provides: the transfer ratio, the molar conductivity detection response, and the relative velocity slope. This allows the assessment of the indirect detection, conductivity detection and peak broadening (distortion) due to electromigration dispersion. Also, we present a spectral decomposition of the matrix M to matrices allowing the assessment of the amplitudes of system eigenpeaks (system peaks). Our model predicted the existence of BGEs having no stationary injection zone (or water zone, gap, peak, dip). A common practice of using the injection zone as a marker of the electroosmotic flow must fail in such electrolytes.
Eigenmobilities in background electrolytes for capillary zone electrophoresis: IV. Computer program PeakMaster
Authors: Jaroš Michal , Hruška Vlastimil , Štědrý Milan , Zusková Iva , Gaš Bohuslav
Published: October 2004

We are introducing a computer implementation of the mathematical model of zone electrophoresis (CZE) described in Štědrý, M., Jaroš, M., Hruška, V., Gaš, B., Electrophoresis 2004, 25, 3071–3079 program PeakMaster. The computer model calculates eigenmobilities, which are the eigenvalues of the matrix tied to the linearized continuity equations, and which are responsible for the presence of system eigenzones (system zones, system peaks). The model also calculates other parameters of the background electrolyte (BGE) – pH, conductivity, buffer capacity, ionic strength, etc., and parameters of the separated analytes – effective mobility, transfer ratio, molar conductivity detection response, and relative velocity slope. This allows the assessment of the indirect detection, conductivity detection and peak broadening (peak distortion) due to electromigration dispersion. The computer model requires the input of the BGE composition, the list of analytes to be separated, and the system instrumental configuration. The output parameters of the model are directly comparable with experiments; the model also simulates electropherograms in a user‐friendly way. We demonstrate a successful application of PeakMaster for inspection of BGEs having no stationary injection zone.
Determination of the bacterial pathogen Edwardsiella tarda in fish species by capillary electrophoresis with blue light‐emitting diode‐induced fluorescence
Authors: Yu Lijun , Yuan Lingling , Feng Huatao , Li Sam Fong Yau
Published: October 2004

High‐performance capillary electrophoresis (HPCE) has been applied to the identification, separation, and quantitation of intact bacteria. We demonstrate that a pathogen (Edwardsiella tarda) which causes systemic infection in commercially important fish species can be rapidly identified and determined (<10 min) after direct injection into fish fluid by CE blue light‐emitting diode (LED)‐induced fluorescence. SYTO 13 (488 nm/509 nm), a cell‐permeable green nucleic acid stain, was used to stain the cells. Remarkably high efficiency (>1 200 000 theoretical plates/m) was achieved with this rapid and efficient CE method. It was found that proper sample vortexing (90 s) would be beneficial to disperse aggregated cells and facilitate the focusing of intact cells during electrophoresis. Ionization of the surface constituents of Edwardsiella tarda cells provided efficient surface charges for the intact cells to be separated from the EOF and damaged or lysed cells when the separation was performed in running buffer (3.94 mM Tris, 0.56 mM borate, 0.013 mM EDTA) at pH 10.5. The limit of detection (LOD) and recovery were found to be 4.2×104 cells/mL and 70.0%, respectively. This proposed CE method could become an effective tool for diagnosis and tracking of certain diseases caused by bacteria in fish species as well as in human beings.
Investigation of the novel mixed‐mode stationary phase for capillary electrochromatography. II. Separation of amino acids and peptides on sulfonated naphthalimido‐modified silyl silica gel
Authors: Ohyama Kaname , Shirasawa Yumi , Wada Mitsuhiro , Kishikawa Naoya , Ohba Yoshihito , Nakashima Kenichiro , Kuroda Naotaka
Published: October 2004

The potential of 3‐(4‐sulfo‐1,8‐naphthalimido)propyl‐modified silyl silica gel (SNAIP) as a mixed‐mode stationary phase for capillary electrochromatography (CEC) was investigated for the separation of charged analytes, taking four amino acids (tyrosine, phenylalanine, tryptophan, histidine) as model analytes. The elution process of these charged analytes in CEC with SNAIP was dominated by a combination of both electrophoretic process and chromatographic process involving hydrophobic as well as electrostatic interactions. In order to study the retention mechanism, the CEC retention factor k* and the velocity factor ke* were measured for the amino acids, which allowed the assessment of the respective contribution from the differential processes underlying the separation. Migration and retention could be mediated by changing various mobile phase compositions, including buffer pH, buffer concentration, and concentration of organic solvent. Based on the results obtained by separation of the amino acids, the separation of eight peptides (Gly‐Val, Gly‐Phe, Gly‐Ile, Gly‐His, Gly‐Lys, Lys‐Lys, Gly‐Gly‐Gly, Gly‐Gly‐His) was attempted. A good separation was achieved under an isocratic elution with a mobile phase consisting of 35 mM phosphate buffer (pH 3.8) and 40% methanol.
Effect of surfactant concentration and buffer selection on chromatographic figures of merit in chiral microemulsion electrokinetic chromatography
Authors: Mertzman Melissa D. , Foley Joe P.
Published: October 2004

The enantiomeric resolution of 15 different pharmaceutical compounds was explored using chiral microemulsion electrokinetic chromatography (MEEKC). The microemulsion employed was comprised of the chiral surfactant dodecoxycarbonylvaline (DDCV), 1‐butanol, and ethyl acetate, at an initial composition of 1% w/v:1.2% v/v:0.5% v/v, respectively. The effect of varying the background buffer composition, voltage, and ultimately the surfactant concentration and/or aggregate phase ratio were examined. Changing from a zwitterionic buffer ((2‐[2‐amino‐2‐oxoethyl)amino]ethanesulfonic acid, ACES) to the same concentration of phosphate buffer improved the efficiency and decreased overall analysis time, but also resulted in a decrease in chiral resolution. Furthermore, using phosphate buffer while simultaneously increasing the percent DDCV from 1 to 4% increased the efficiencies from a range of 34 000 to 59 000 N/m to a range of 160 000 to 400 000 N/m. While the enantioselectivities did not change significantly, the improvement in efficiencies, elution range, and retention factors provided an increase in both resolution and the number of enantiomers that were separated. Using an optimized microemulsion comprised of phosphate buffer and 4% DDCV, chiral separation was achieved for all 11 pairs of enantiomers, with a resolution ranging from 0.90 to 4.71. Moreover, the average resolution doubled in going from nonoptimized to optimized conditions for five of the eleven compounds. Finally, a comparison was made of the effect of increasing only the surfactant concentration by a factor of 4 versus increasing the overall composition (or phase ratio) by a factor of 4. Ultimately, the microemulsion containing 4% DDCV provided a larger elution range, greater resolution, and more optimal retention than that provided by the 4× phase increase.
Intermediate precision study on a capillary electrophoretic method for chlortetracycline
Authors: Dehouck Pieter , Jaggavarapu Phani K. R. , Desmedt Aline , Van Schepdael Ann , Hoogmartens Jos
Published: October 2004

We describe an intermediate precision study on a capillary electrophoretic (CE) method for chlortetracycline. It is shown how in one setup the influence of the factors time, analyst, and equipment on the precision can be investigated. As different types of CE equipments were included, the transferability of the method could be examined. Both the qualitative and quantitative aspect of the method were investigated. It was shown that small adaptations in method conditions can have a large influence on the method transferability. Although the method could be transferred to different types of CE equipments, the precision of the method was found poor when the between‐equipment variability was taken into account. Despite the use of an internal standard, the between injection variability was found rather high.
Proline‐coated column for the capillary electrochromatographic separation of amino acids by in‐column derivatization
Authors: Lin Chun‐Chi , Liu Chuen‐Ying
Published: October 2004

With 3‐trimethoxysilylpropyl chloride as the spacer, a proline‐coated capillary column was prepared for the capillary electrochromatographic (CEC) separation of amino acids by in‐column derivatization. Nine standard mixtures, including aspartic acid, glutamic acid, valine, phenylalanine, alanine, isoleucine, leucine, tyrosine, and tryptophan, were injected. o‐Phthalaldehyde (OPA), OPA/2‐mercaptoethanol (2‐ME) and OPA/N‐acetylcysteine (NAC) in borate buffer were tested as the derivatizing agent. Among them, OPA (50 mM) in borate buffer (pH 9.5, 50 mM) gave the best performance. The formation of isoindole could be detected by UV detection. The sandwich‐type injection was carried out in hydrostatic mode (10 cm) with the program R(10 s)S(10 s) R(10 s)W(10 min) with R, S, and W being the reagent, sample, and waiting times. Mesityl oxide, benzyl alcohol, and acetone showed some interaction with the column. A current monitoring method was used instead of the determination of the electroosmotic flow (EOF). The direction of EOF was from anode to cathode even under acidic condition lower than the pI value (6.31) of the bonded group due to some unreacted silanol groups. Some parameters including pH, nature, and concentration of the mobile phase and the effect of organic modifier with regard to the CEC separation were investigated. With the proline‐coated column (75 (50) cm×75 μm ID) the best separation was performed in phosphate buffer (pH 4.00, 100 mM) with an applied voltage of —15 kV. The established method was also compared with those precolumn derivatized prior to the separation with proline‐coated column as well as with in‐capillary derivatization and separation with a bare fused‐silica column.
New particle‐loaded monoliths for chiral capillary electrochromatographic separation
Authors: Schmid Martin G. , Koidl Julia , Freigassner Christina , Tahedl Sandra , Wojcik Lena , Beesley Thomas , Armstrong Daniel W. , Gübitz Gerald
Published: October 2004

Fritless particle‐loaded monoliths for chiral capillary electrochromatographic (CEC) separation were prepared. Silica particles containing a chiral selector are suspended in a monomer solution, which is drawn into the capillary followed by in situ polymerization. Thereby the silica‐based particles containing the chiral selector are embedded in a nonchiral continuous bed. This kind of chiral stationary phase is inexpensive, easy, and reproducible to prepare and circumvents the preparation of frits. As a model, teicoplanin aglycone as chiral selector bonded to 3 μm silica particles was used. The applicability of this approach is demonstrated by means of the chiral separation of aliphatic and aromatic amino acids and dipeptides. As a further application, the chiral selector ristocetin A bonded to 3 μm silica particles was used for the enantiomeric separation of chiral α‐hydroxy acids. Since α‐hydroxy acids migrate toward the anode, a cationic charge‐providing agent was copolymerized with the matrix. This served to reverse the direction of the electroosmatic flow (EOF).
Microemulsion electrokinetic chromatography for the analysis of acrylamide in food
Authors: Bermudo Elisabet , Ruiz‐Calero Victoria , Puignou Lluis , Galceran Maria T.
Published: October 2004

The influence of microemulsion electrokinetic chromatography (MEEKC) operating conditions, such as the type of water‐immiscible alcohol, aqueous phosphate buffer concentration, pH, as well as the addition of methanol and 2‐propanol, on acrylamide migration has been studied. These parameters have been optimized taking into account the presence of matrix signals, in order to avoid the interference of these peaks in acrylamide determination. The best separations were achieved using a microemulsion consisting of 0.8% m/v n‐amyl alcohol, 3.3% m/v sodium dodecyl sulfate (SDS), 6.6% m/v 1‐butanol, and 89.3% m/v 40 mM phosphate buffer at pH 6.5 working at 15 kV in uncoated silica capillaries. Linear calibration curves over the range studied (1.25–125 μg·mL‐1), the detection limit (0.70 μg·mL‐1), and both run‐to‐run (up to 3.4% for concentration and 1.6% for time values) and day‐to‐day precision (lower than 11.6% for concentration) have been established. Finally, the applicability of the MEEKC method developed has been demonstrated by analyzing levels of acrylamide present in samples of home‐made French fries.
Large‐scale carbohydrate analysis by capillary array electrophoresis: Part 1. Separation and scale‐up
Authors: Khandurina Julia , Olson Nels A. , Anderson Abraham A. , Gray Kevin A. , Guttman Andras
Published: October 2004

A 96‐capillary array electrophoresis (CAE) instrument has been adapted for large‐scale mono‐ and oligosaccharide analysis and characterization. Operational protocols and data processing tools have been developed to optimize the CAE system for this application. Effects of different additives to the running buffer on efficiency and capillary‐to‐capillary performance reproducibility have been studied.
Large‐scale carbohydrate analysis by capillary array electrophoresis: Part 2. Data normalization and quantification
Authors: Khandurina Julia , Anderson Abraham A. , Olson Nels A. , Stege Justin T. , Guttman Andras
Published: October 2004

Automated 96‐capillary array electrophoresis (CAE) methodology described in the first part of the present work offered large‐scale high‐performance profiling of oligo‐ and monosaccharides to fulfill the needs of bioindustrial laboratories. Sensitivity at low nanomolar concentration, good resolving power and reliability achieved in the experiments is invaluable for monitoring reaction products from enzymatic polysaccharide digestion with numerous applications in agricultural, chemical and food industries. In addition to optimization of mono‐ and oligosaccharide separations in CAE system and necessary operational protocol modifications, capillary‐to‐capillary and run‐to‐run variation in migration time and signal intensity necessitated development of data normalization tools. Internal fluorescent standards have been incorporated into the analysis aiding migration time normalization and CAE trace alignment. Data processing, visualization, and programming tools have been developed along with quantification approaches.
High‐throughput capillary electrophoresis frontal analysis method for the study of drug interactions with human serum albumin at near‐physiological conditions
Authors: Martínez‐Pla Juan J. , Martínez‐Gómez María A. , Martín‐Biosca Yolanda , Sagrado Salvador , Villanueva‐Camañas Rosa M. , Medina‐Hernández Maria J.
Published: October 2004

The application of the short‐end capillary injection to capillary electrophoresis frontal analysis (CE‐FA) to study the interaction between basic, neutral and acid drugs towards human serum albumin (HSA) at near‐physiological conditions is presented. The compounds selected display a wide range of binding affinities and the results obtained were in good agreement with those reported in the literature. An equation for the estimation of the number of primary binding sites and their corresponding affinity constants is developed isolating the experimentally measured variables in just one axis. The proposed CE‐FA method to screen drug interactions with HSA under physiological conditions is simple, rapid and cost‐effective what may facilitate its implementation in the drug discovery process.
Streaming current measurements in zirconia‐coated capillaries
Authors: Crosnier de Bellaistre Myriam , Renaud Louis , Kleimann Pascal , Morin Pierre , Randon Jérôme , Rocca Jean‐Luis
Published: October 2004

The electroosmotic flow created in zirconia‐modified capillaries has been previously investigated. In this paper, we compared the electroosmotic data set with streaming current measurements and we related all these data through ζ‐potential. Streaming current measurements give an excellent indication on the direction and the value of the electroosmotic mobility of an electrolyte/capillary system for a large set of experimental conditions: 2 < pH < 12, 0 < ACN < 80 %, 10‐4 M < [SO2‐ 4 ] < 4×10‐2 M. A good correlation between ζ‐potential from streaming current measurements and ζ‐potential from electroosmotic mobility measurements was observed (r2 = 0.95). However, the values obtained from streaming current were always slightly lower than the one calculated from electroosmotic mobility (slope = 0.86, σ = 0.06). In zirconia‐coated capillaries the ζ‐potential can be tuned from ‐50 to +100 mV depending on the composition of the electrolyte.
Complexation between low‐molecular‐weight cationic ligands and negatively charged polymers as studied by capillary electrophoresis frontal analysis
Authors: Østergaard Jesper , Khanbolouki Abbas , Jensen Henrik , Larsen Claus
Published: October 2004

The potential of using capillary electrophoresis frontal analysis for the study of low‐molecular‐weight ligand‐polyelectrolyte interactions was assessed. The interaction of the ligands 1‐propylpyridinium bromide, 2‐propylisochinolinium bromide, and paraquat with the polymer dextran sulfate was investigated as a function of polymer concentration and ionic strength of the buffer solution. Linear binding isotherms were obtained and association constants were determined. The complex formation was independent of the dextran sulfate concentration at low ionic strength. Ligand‐polyelectrolyte interactions were strongly dependent on the ionic strength. The interaction of the divalent cation paraquat with the dextran sulfate was much stronger than the interactions of the monovalent cationic ligands with the polyelectrolyte. The binding data obtained were in accord with results obtained by equilibrium dialysis. Capillary electrophoresis frontal analysis has the potential to become a valuable tool for characterization of ligand‐polyelectrolyte interactions in drug design as well as in other areas.