bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractFive 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

AbstractA 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

AbstractA 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

AbstractWe 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

AbstractHigh‐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

AbstractThe 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

AbstractThe 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

AbstractWe 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

AbstractWith 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

AbstractFritless 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

AbstractThe 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

AbstractA 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

AbstractAutomated 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.