bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microfluidics for Miniaturized Laboratories on a Chip
Authors: Franke Thomas A. , Wixforth Achim 
Published: October 2008

AbstractMicrofluidic systems promise solutions for high throughput and highly specific analysis for biology, medicine and chemistry while consuming only tiny amounts of reactants and space. On these lab‐on‐a‐chip platforms often multiple physical effects such as electrokinetic, acoustic or capillary phenomena from various disciplines are exploited to gain the optimal functionality. The fluidics on these small length scales differ significantly from our experience of the macroscopic world. In this Review we survey some of the approaches and techniques to handle minute amounts of fluid volumes in microfluidic systems with special focus on surface acoustic wave driven fluidics, a technique developed in our laboratory. Here, we outline the basics of this technique and demonstrate, for example, how acoustic mixing and fluid actuation is realized. Furthermore we discuss the interplay of different physical effects in microfluidic systems and illustrate their usefulness for several applications.
Easily Accessible Mono‐ and Polytopic ­β‐Cyclodextrin Hosts by Click Chemistry
Authors: Mourer Maxime , Hapiot Frédéric , Tilloy Sébastien , Monflier Eric , Menuel Stéphane 
Published: October 2008

AbstractA great variety of mono‐ and polytopic β‐cyclodextrin hosts have been easily synthesized by using the CuI‐catalyzed azide–alkyne cycloaddition reaction. Of particular interest for their multibinding properties, dimeric and trimeric CD compounds were obtained by “clicking” mono‐6‐azido‐β‐cyclodextrin derivatives with flexible or rigid dialkynyl spacers. The reaction is general, high‐yielding for some of the synthesized molecules (>80 %) and proceeds under mild conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Advances in separation science applied to metabonomics
Authors: Xiayan Li , Legido‐Quigley Cristina 
Published: October 2008

AbstractMetabonomics focuses on metabolite profile changes in diverse living systems caused by a biological perturbation. These metabolite signatures can be achieved with techniques such as gas chromatography, high‐performance liquid chromatography (ultra‐high‐performance/pressure liquid chromatography and capHPLC), capillary electrophoresis, and capillary electrochromatography normally hyphenated with MS. In this review we present the latest developments of the abovementioned techniques applied in the field of metabonomics, with applications covering phytochemistry, toxicology and clinical research.
Evaluation of a molecularly imprinted polymer as in‐line concentrator in capillary electrophoresis
Authors: Lara Francisco J. , Lynen Fréderic , Sandra Pat , García‐Campaña Ana M. , Alés‐Barrero Fermín 
Published: October 2008

AbstractMolecularly imprinted polymers (MIPs) have been evaluated as sorbent for the construction of an in‐line solid phase extraction concentrator in capillary electrophoresis to be applied in the monitoring of triazine herbicides: atrazine and its three metabolites, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine. Initially, the electrophoretic separation of these compounds was optimized. The electrolyte consists of an aqueous solution of 75 mM phosphoric acid (H3PO4) adjusted to pH 2.1 and containing 0.7 mM cetyltrimethylammonium bromide. After the fabrication and assembly of the concentrator into the capillary, these optimal CE conditions were applied to evaluate the performance of this device. Efficiencies of 40 000–55 000 plates could be achieved and the separation time was around one hour. Different parameters affecting the in‐line molecularly imprinted solid‐phase extraction in capillary electrophoresis such as composition and volume of the elution plug were optimized. The method was evaluated in terms of linearity, precision and limits of detection and quantification. MIPs were compared with Oasis® hydrophilic‐lipophilic‐balance (HLB) particles for the in‐line coupling of solid‐phase extraction and capillary electrophoresis. The superior selectivity of MIPs is demonstrated through direct injection of a urine sample spiked with 10 μg/mL atrazine, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine. Recoveries were between 92 and 102% compared with an aqueous solution.
Preparation and evaluation of butyl acrylate‐based monolithic columns for CEC using ammonium peroxodisulfate as a chemical initiator
Authors: Cantó‐Mirapeix Amparo , Herrero‐Martínez José Manuel , Mongay‐Fernández Carlos , Simó‐Alfonso Ernesto F. 
Published: October 2008

AbstractAcrylate‐ester‐based monoliths for CEC using peroxodisulfate as a chemical initiator were prepared. The influence of two ternary porogenic solvents on the physical and chromatographic properties of butyl acrylate monolithic stationary phases was investigated. The composition and the ratio of porogenic solvent were adjusted to obtain highly permeable rigid monoliths with adequate column efficiency. Among the prepared butyl acrylate monoliths, those polymerized from a ternary porogenic solvent of acetonitrile/ethanol/water exhibited the most promising performance with a minimum plate height for naphthalene of 10.5 µm and a bed permeability of 7.3×10−14 m2. A comparison in terms of efficiency and permeability with thermal and UV initiation using α,α′‐AIBN was also performed. The resulting monolithic stationary phases were evaluated in terms of reproducibility, giving RSD values below 5.1% in the electrochromatographic properties studied.
Sample stacking for the analysis of penicillins by microemulsion electrokinetic chromatography
Authors: Huang Hsi‐Ya , Hsieh Shih‐Huan 
Published: October 2008

AbstractIn this study, on‐line sample concentration methods, which coupled field‐amplified sample injection and sweeping technology with MEEKC, were used to detect and analyze eight common penicillin antibiotics (nafcillin, dicloxacillin, ampicillin, oxacillin, penicillin V, cloxacillin, penicillin G, and amoxicillin). During the optimization of field‐amplified sample injection‐sweeping MEEKC, the composition of sample matrix and the length of acidic plug were found to be the predominant influences for penicillin stacking. Both zwitterionic ampicillin and amoxicillin could only be stacked through cation‐selective‐exhaustive‐injection sweeping, whereas the other six penicillin compounds were found to be concentrated by anion‐selective‐exhaustive‐injection sweeping. Hence, in order to simultaneously concentrate the eight penicillins in a single‐run sweeping step, a combination of successive anion‐ and cation‐selective injections was used. When compared with previous CE‐UV methods, the proposed on‐line concentration MEEKC method provided better detection sensitivity and faster separation for these penicillins either in single ion‐selective injection or in successive anion‐/cation‐selective injection where the LODs were in the range of 0.2–2.8 µg/L and 0.5–5.8 µg/L, respectively.
A mesoporous silica nanoparticles immobilized open‐tubular capillary column with a coating of cellulose tris(3,5‐dimethylphenyl‐carbamate) for enantioseparation in CEC
Authors: Dong Xiaoli , Wu Ren'an , Dong Jing , Wu Minghuo , Zhu Yan , Zou Hanfa 
Published: October 2008

AbstractAn approach of immobilizing mobile crystalline material (MCM)‐41 mesoporous silica nanoparticles on the inner wall of an open‐tubular (OT) capillary as the support for coating chiral selector of cellulose tris(3,5‐dimethylphenyl‐carbamate) (CDMPC) was carried out. By taking advantage of the improved phase ratio of OT capillary with the immobilization of MCM‐41 mesoporous material, the cellulose derivative of CDMPC as the chiral selector was simply coated on the MCM‐41 nanoparticle layer via the hydrogen‐bonding interaction, and the enantioseparation was successively carried out. Eight pairs of acidic, neutral and basic enantiomers were resolved in capillary electrochromatography or capillary liquid chromatography mode. The concentration of CDMPC for coating was systematically investigated to obtain the optimized chromatographic properties on enantioseparation by controlling the supposed film thickness of CDMPC on MCM‐41 nanoparticle layer. Comparing with a bare fused silica capillary column coated with CDMPC under the same coating procedure as MCM‐41‐modified capillary did, the MCM‐41‐modified capillary column offered much higher enantioselectivity. This result indicated the significance of using the mesoporous nanoparticles as the electrochromatographic support to enhance the phase ratio of OT capillary column in capillary electrochromatography and capillary liquid chromatography. For investigating the effect of experimental conditions on the enantioseparation with this prepared OT capillary column, the content of organic modifier acetonitrile in the mobile phase was thus extensively evaluated to achieve a better chiral separation.
Stacking enhanced determination of steroids by CE
Authors: Bykova Liliya , Holland Lisa A. 
Published: October 2008

AbstractThis study outlines a simple method for pH‐mediated stacking of natural and synthetic steroids facilitated with carboxymethyl‐β‐CD. Sample stacking (10 kV, 60 s) is accomplished with 23 mM carboxymethyl‐β‐CD in 50 mM 3‐[cyclohexylamino]‐1‐propanesulfonic acid buffered at pH 10. Following stacking, steroidal compounds are separated in less than 5 min with a running buffer of 13 mM hydroxypropyl‐β‐CD, 30 mM SDS in 200 mM phosphate buffered at pH 2.5. Using a 60 s electrokinetic injection, the limits of detection of estradiol, ethynyl estradiol, estrone, hydroxyprogesterone, progesterone, and 11‐ketotestosterone range from 2 to 14 nM. For all steroids, the within‐day and day‐to‐day reproducibility in migration time is ≤1 and ≤2% RSD, respectively. The within‐day and day‐to‐day reproducibility in peak area is ≤9 and ≤22% RSD, respectively. The method is applied to fish plasma and holds potential to profile multiple steroids in a single biological sample.
Using multiple PCR and CE with chemiluminescence detection for simultaneous qualitative and quantitative analysis of genetically modified organism
Authors: Guo Longhua , Qiu Bin , Chi Yuwu , Chen Guonan 
Published: October 2008

AbstractIn this paper, an ultrasensitive CE–CL detection system coupled with a novel double‐on‐column coaxial flow detection interface was developed for the detection of PCR products. A reliable procedure based on this system had been demonstrated for qualitative and quantitative analysis of genetically modified organism—the detection of Roundup Ready Soy (RRS) samples was presented as an example. The promoter, terminator, function and two reference genes of RRS were amplified with multiplex PCR simultaneously. After that, the multiplex PCR products were labeled with acridinium ester at the 5′‐terminal through an amino modification and then analyzed by the proposed CE–CL system. Reproducibility of analysis times and peak heights for the CE–CL analysis were determined to be better than 0.91 and 3.07% (RSD, n=15), respectively, for three consecutive days. It was shown that this method could accurately and qualitatively detect RRS standards and the simulative samples. The evaluation in terms of quantitative analysis of RRS provided by this new method was confirmed by comparing our assay results with those of the standard real‐time quantitative PCR (RT‐QPCR) using SYBR® Green I dyes. The results showed a good coherence between the two methods. This approach demonstrated the possibility for accurate qualitative and quantitative detection of GM plants in a single run.
Size‐based characterization of nanometric cationic maghemite particles using capillary zone electrophoresis
Authors: d'Orlyé Fanny , Varenne Anne , Gareil Pierre 
Published: October 2008

AbstractSize‐sorted maghemite (γ‐Fe2O3) particle populations of number mean solid diameters ranging from 6 to 10 nm were suspended and directly characterized in their stabilizing acidic, citrated or basic aqueous media using CZE coupled with UV detection. Analytical conditions were optimized in order to ensure reliable mobility measurements of these ferrofluids in their anionic and cationic forms. Particular interest has been paid to the investigation of the positively charged ferrofluids since cationic colloids have received little attention so far. A strategy for capillary wall modification was chosen in order to prevent particle adsorption while preserving high analytical performances. The influence of experimental conditions such as particle volume fraction, injection volume, electric field strength and electrolyte nature on electrophoretic profiles and measured electrophoretic mobilities was evaluated. A size‐dependent electrophoretic mobility was demonstrated and discussed in terms of the ratio of the particle radius to Debye length with reference to existing models (Henry, etc.). Although these nanometric particle distributions lie in a very narrow size range, partial separation was obtained with selectivity varying as a function of electrolyte ionic strength.
Chiral separation of dansyl amino acids by ligand exchange capillary electrochromatography in a low molecular weight organogel
Authors: Mizrahi Shaul , Rizkov Dan , Shames Alexander I. , Lev Ovadia 
Published: October 2008

AbstractChiral electroseparation is demonstrated, for the first time, by a low molecular weight organogel filled capillary. Five pairs of dansylated amino acids were separated by copper ligand exchange on a trans‐(1S,2S)‐1,2‐bis‐(dodecylamido) cyclohexane (1) gel in methanol. Low molecular weight organogels are emerging materials that form stable, fibrillar, thermoreversible and thixotropic gels without covalent bonding of their monomeric building blocks. The dependence of chiral resolution and complex formation stability on the pH*, the ratio between copper and the D‐valine selector, as well as other parameters were investigated revealing trends that were unparalleled in previously reports on copper ligand exchange of dansylated amino acids. These observations were explained in view of a simple stacking model of (1) and the difference in axial ligation of the amide carbonyl backbone of the gel to the dansyl D‐ or L‐amino acid:D‐valine:copper ternary complexes.
Development of electrophoretically mediated microanalysis method for the kinetics study of flavin‐containing monooxygenase in a partially filled capillary
Authors: Hai Xin , Konečnỳ Jiří , Zeisbergerová Marta , Adams Erwin , Hoogmartens Jos , Schepdael Ann Van 
Published: October 2008

AbstractAn electrophoretically mediated microanalysis method with a partial filling technique was developed for flavin‐containing monooxygenase, form 3 (FMO3). The in‐line enzymatic reaction was performed in 100 mM phosphate reaction buffer (pH 7.4) whereas 150 mM phosphate buffer (pH 3.3) was used as a background electrolyte. A long plug of cofactor NADPH dissolved in reaction buffer was hydrodynamically injected into a fused‐silica capillary, followed by enzyme and substrate solution. The reaction was initiated at 37°C in the thermostated part of the cartridge by the application of 9 kV for 0.9 min. The voltage was turned off to increase the product amount (zero‐potential amplification) and again turned on at a constant voltage of 10 kV to elute all the components. Direct detection was performed at 191 nm. The developed electrophoretically mediated microanalysis method was applied for the kinetics study of FMO3 using clozapine as a substrate probe. A Michaelis–Menten constant (Km) of 410.3 µM was estimated from the corrected peak area of the product, clozapine N‐oxide. The calculated value of the maximum reaction velocity (Vmax) was found to be 1.86 nmol/nmol enzyme/min. The acquired FMO3 kinetic parameters are in accordance with the published literature data.
Retention of proteins and metalloproteins in open tubular capillary electrochromatography with etched chemically modified columns
Authors: Pesek Joseph J. , Matyska Maria T. , Salgotra Vasudha 
Published: October 2008

AbstractEtched chemically modified capillaries with two different bonded groups (pentyl and octadecyl) are compared for their migration behavior of several common proteins and metalloproteins as well as metalloproteinases. Migration times, efficiency and peak shape are evaluated over the pH range of 2.1–8.1 to determine any effects of the bonded group on the electrochromatographic behavior of these compounds. One goal was to determine if the relative hydrophobicity of the stationary phase has a significant effect on proteins in the open tubular format of capillary electrochromatography as it does in HPLC. Reproducibility of the migration times is also investigated.
Use of a heterogeneous buffer combination in microchip electrophoresis for high‐resolution separation by on‐line concentration of DNA samples
Authors: Nagata Hideya , Ishikawa Mitsuru , Yoshida Yuichiro , Tanaka Yoshio , Hirano Ken 
Published: October 2008

AbstractWe have developed a novel high‐resolution separation technique of DNA fragments in a heterogeneous combination of a sample buffer and a separation buffer. The use of a heterogeneous buffer combination is a simple method for on‐line concentration of DNA fragments, in which a sample buffer is simply exchanged with one including taurine anions. The mobility of taurine anions, co‐ions for DNA, is lower than the that of acetate anions in a separation buffer. The difference in the mobility invokes transient isotachophoresis. The current technique allows DNA fragments to be effectively concentrated and the separation length of microchips to be shorter than that of conventional ones by a factor of three without deterioration in separation resolution and any modification of a chip design. Fragments of 100‐bp DNA ladders (100–1000 bp) were separated with high resolution (0.72–10.7) within 60 s with a 10 mm separation length on a polymethyl methacrylate chip. Furthermore, fragments of 10‐bp DNA ladders (10–330 bp) were separated with high resolution (0.69–2.00) with a 10 mm separation length within 50 s without band broadening. The current achievements will make it possible to fabricate compact devices for microchip electrophoresis.
Chemometrical examination of active parameters and interactions in flow injection‐capillary electrophoresis
Authors: Dahdouh Froseen T. , Clarke Keith , Salgado Marisol , Hanrahan Grady , Gomez Frank A. 
Published: October 2008

AbstractThe first detailed examination of flow injection‐capillary electrophoresis (FI‐CE) active parameters and their interactions via response surface methodology (RSM) is presented. Specifically, RSM in the form of a Box–Behnken design was implemented to effectively predict the significance of capillary length, voltage and injection volume on the optimization of an in‐house built FI‐CE analyzer. Initial studies were performed assessing peak height and peak shape of the model compound N,N‐dimethylformamide. Optimum model conditions were then derived and used in the model separation of two small molecules, nicotinamide adenine dinucleotide, reduced form (NADH) and benzenesulfonamide. By implementing the RSM approach, detailed examination of active FI‐CE parameters was possible, including the ability to reveal a significant interactive effect. This work is not only highly significant for advancing FI‐CE developments, but instructive for investigators actively exploring other coupled analytical techniques and associated experimental parameters.
Evaluation of carrier ampholyte‐based capillary electrophoresis for separation of peptides and peptide mimetics
Authors: Koval Dušan , Busnel Jean‐Marc , Hlaváček Jan , Jiráček Jiří , Kašička Václav , Peltre Gabriel 
Published: October 2008

AbstractCarrier ampholyte‐based capillary electrophoresis (CABCE) has recently been introduced as an alternative to CE (CZE) in the classical buffers. In this study, isoelectric BGEs were obtained by fractionation of Servalyt pH 4–9 carrier ampholytes to cuts of typical width of 0.2 pH unit. CABCE feasibility was examined on a series of insect oostatic peptides, i.e. proline‐rich di‐ to decapeptides, and phosphinic pseudopeptides – tetrapeptide mimetics synthesized as a mixture of four diastereomers having the –P(O)(OH)–CH2– moiety embedded into the peptide backbone. With identical selectivity, the separation efficiency of CABCE proved to be as good as classical CE for the insect oostatic peptides and better for diastereomers of the phosphinic pseudopeptides. In addition, despite the numerous species present in the narrow pH cuts of carrier ampholytes, CABCE seems to be free of system zones that could hamper the analysis. Peak symmetry was good for moderately to low mobile peptides, whereas some peak distortion due to electromigration dispersion, was observed for short peptides of rather high mobility.
Carboxylic multi‐walled carbon nanotubes as immobilized stationary phase in capillary electrochromatography
Authors: Sombra Lorena , Moliner‐Martínez Yolanda , Cárdenas Soledad , Valcárcel Miguel 
Published: October 2008

AbstractCarboxylic multi‐walled carbon nanotubes (c‐MWNT) have been immobilized into a fused‐silica capillary for capillary electrochromatography. The c‐MWNT were successfully incorporated after the silanization and coupling with glutaraldehyde on the inner surface of the capillary. The electrochromatographic features of the c‐MWNT immobilized stationary phase have been evaluated for the analysis of different compounds of pharmaceutical interest. The results indicated high electrochromatographic resolution, good capillary efficiency and retention factors. In addition, highly reproducible results between runs, days and capillaries were obtained.
Development of a capillary electrophoresis‐based assay of sirtuin enzymes
Authors: Fan Yi , Ludewig Ronny , Imhof Diana , Scriba Gerhard K. E. 
Published: October 2008

AbstractSirtuins are a family of nicotinamide adenine dinucleotide (NAD+)‐dependent enzymes catalyzing the deacetylation of acetyl‐lysine residues of histones and other proteins. Three 9‐fluorenylmethoxycarbonyl (Fmoc)‐labeled peptide substrates derived from the amino acid sequence of p53, i.e. Fmoc‐KK(Ac)‐NH2, Fmoc‐KK(Ac)L‐NH2 and Fmoc‐RHKK(Ac)‐NH2, were synthesized and evaluated as substrates of the human isoenzyme SIRT1. The acetylated and respective deacetylated peptides as well as nicotinamide as the reaction product of nicotinamide adenine dinucleotide were separated by capillary electrophoresis in a fused‐silica capillary using 200 mM phosphate‐Tris buffer, pH 2.7. Sodium hydroxide‐mediated sample stacking was performed in order to overcome peak asymmetry due to the high salt and acid content of the sample as well as to enhance UV detection sensitivity. The assay was subsequently validated. Upon incubation of the acetylated peptides for 60 min in the presence of 2.5 U of SIRT1 at least 87% of the peptides was deacetylated, indicating that the new derivatives are efficient substrates of the enzyme.