bluuebunny/crossref_metadata_2025_split huggingface dataset:
On‐line identification of trans‐resveratrol in red wine using a sweeping technique combined with capillary electrophoresis/77 K fluorescence spectroscopy
Authors: Hsieh Min‐Chi , Lin Cheng‐Huang 
Published: February 2004

AbstractThe feasibility of combining the techniques of on‐line concentration and capillary electrophoresis/low‐temperature fluorescence spectroscopy (CE/LTFS) for the detection and identification of trans‐resveratrol in red wine at 77 K is demonstrated for the first time. This technique, involving sweeping‐micellar electrokinetic chromatography (sweeping‐MEKC), was used for the initial on‐line concentration and separation, after which a cryogenic molecular fluorescence experiment was performed at 77 K. In comparison with normal‐MEKC mode, a ∼1500‐fold improvement in detection sensitivity could be obtained when the sweeping‐MEKC was applied. The proposed method permits not only the separation and detection of trans‐resveratrol from red wine extracts but also ensures that the on‐line spectrum is readily distinguishable and can be unambiguously assigned at 77 K.
Capillary electrophoresis with laser‐induced fluorescence detection as a novel sensitive approach for the analysis of desmosines in real samples
Authors: Annovazzi Laura , Viglio Simona , Perani Eleonora , Luisetti Maurizio , Baraniuk James , Casado Begoña , Cetta Giuseppe , Iadarola Paolo 
Published: February 2004

AbstractAmong various biomarkers believed to behave as descriptors of the disease process in chronic obstructive pulmonary disease (COPD), urinary desmosines are commonly used for monitoring elastin degradation. Given the low concentrations of urinary desmosines, their quantitative determination in this biological matrix often requires preconcentration steps. To minimize both solute losses and effects of sample matrix, and to decrease data variability related to the above‐mentioned manipulation processes, we have developed a capillary electrophoresis approach combined with laser‐induced fluorescence (CE‐LIF) detection system using urine samples not submitted to any pretreatment procedure other than filtering the sample. Urines were hydrolyzed, derivatized with fluoresceine isothiocyanate (FITC) and endogenous desmosines were identified by addition of standard analytes and submitting to mass spectrometry (MS) analysis the material collected from micropreparative runs. The assay showed good linearity, reproducibility and precision, allowing to detect amounts of desmosines as low as 10‐8 M (equivalent to 0.1 fmol on column). We conclude that CE‐LIF technique is a highly sensitive method for detecting urinary desmosines.
Reversed‐phase capillary electrochromatography for the simultaneous determination of acetylsalicylic acid, paracetamol, and caffeine in analgesic tablets
Authors: Pucci Vincenzo , Mandrioli Roberto , Raggi Maria Augusta , Fanali Salvatore 
Published: February 2004

AbstractThe separation and simultaneous determination of caffeine, paracetamol, and acetylsalicylic acid in two analgesic tablet formulations was investigated by capillary electrochromatography (CEC). The effect of mobile phase composition on the separation and peak efficiency of the three analytes was studied and evaluated; in particular, the influence of buffer type, buffer pH, and acetonitrile content of the mobile phase was investigated. The analyses were carried out under optimized separation conditions, using a full‐packed silica capillary (75 μm ID; 30.0 cm and 21.5 cm total and effective lengths, respectively) with a 5 μm C8 stationary phase. A mixture of 25 mM ammonium formate at pH 3.0 and acetonitrile (30:70 v/v) was used as the mobile phase. UV detection was at 210 nm. Good linearity was found in the range of 50–200, 20–160, and 4–20 μg/mL for acetylsalicylic acid (r2 = 0.9988), paracetamol (r2 = 0.9990) and caffeine (r2 = 0.9990), respectively. Intermediate precision (RSD interday) as low as 0.1–0.8% was found for retention times, while the RSD values for the peak area ratios (Aanalyte/AIS) were in the range of 1.9–2.9%. The optimized CEC method was applied to the analysis of the studied compounds present in commercial tablets.
Chiral recognition of binaphthyl derivatives using electrokinetic chromatography and steady‐state fluorescence anisotropy: Effect of temperature
Authors: Billiot Fereshteh Haddadian , McCarroll Matthew C. , Billiot Eugene J. , Warner Isiah M. 
Published: February 2004

AbstractThe effect of temperature on the chiral recognition of binaphthyl derivatives in the presence of poly sodium N‐undecanoyl‐LL‐leucyl‐leucinate (poly LL‐SULL) is examined using electrokinetic chromatography (EKC) and steady‐state fluorescence anisotropy. An examination of the effect of temperature suggests that the chiral recognition of 1,1'‐binaphthyl‐2,2'‐diol enantiomers improves with increasing temperature, whereas lower temperatures resulted in better enantiosolectivity in the case of 1,1'‐binaphthyl‐2,2'‐diyl hydrogen phosphate enantiomers. In addition, steady‐state fluorescence anisotropy results show that the anisotropy of the two enantiomers are different when complexed to poly‐(LL) SULL. As would be expected, the enantiomer that binds stronger to the chiral pseudostationary phase, as evidenced by EKC experiments, had higher anisotropy values. The results of this study suggest that steady‐state fluorescence anisotropy can be used to gain further insight into chiral recognition.
Capillary electrochromatography of Triton X‐100
Authors: Norton Dean , Shamsi Shahab A. 
Published: February 2004

AbstractNonionic surfactants such as Triton X‐100 (TX‐100) are comprised of a mixture of oligomers with a varying degree of length in the ethoxylate chain. The development of chromatographic methods for resolution of the various oligomers of TX‐100 is of environmental importance, and can be useful for quality control and characterization in industrial manufacture. Capillary electrochromatography (CEC) is fast becoming a capable separation technique that combines the benefits of both high‐performance liquid chromatography (HPLC) and capillary electrophoresis (CE). This report presents a novel CEC method for separation of the various TX‐100 oligomers. A comparison of monomeric vs. polymeric stationary phases for separation of TX‐100 was conducted. Since the oligomers of TX‐100 were better resolved on a monomeric phase as compared to polymeric phase, a systematic mobile phase tuning was performed utilizing a monomeric CEC‐C18‐3 μm‐100 Å stationary phase. Various mobile phase parameters such as acetonitrile (ACN) content, Tris concentration, pH, voltage, and temperature were manipulated in order to achieve the optimum separation of oligomers in less than 30 min.
Indirect resolution of ß‐blocker agents by reversed‐phase capillary electrochromatography
Authors: Aturki Zeineb , Vichi Francesca , Messina Antonella , Sinibaldi Massimo 
Published: February 2004

AbstractThe indirect resolution of five β‐adrenoreceptor blocking agents (propranolol, oxprenolol, pindolol, metoprolol, and atenolol) using precolumn derivatization with (+)‐1‐(9‐fluorenyl)ethyl chloroformate (FLEC), and capillary electrochromatography (CEC) is reported. Three octadecylsilanized (ODS) silica gel‐based stationary phases, differing in particle diameter and carbon surface density for suitability of determination of the enantiomeric composition of these substances in drugs and biological fluids, were studied. Under optimum separation conditions, all the investigated compounds were baseline‐resolved within acceptable analysis times (i.e., between 10–16 min). The resolution values ranged between 1.80 and 1.14, and the separation factors were in no case less than 1.07. The possible use of the developed CEC method for the determination of enantiomeric composition of β‐adrenoreceptor blocking agents in drug substances was investigated. A study, in which the enantiomers of metoprolol were examined regarding specificity, reproducibility, limit of detection, and ruggedness, was developed in accordance with some analytical procedures for method validation.
Dynamics of interconversion of enantiomers in chiral separation systems: A novel approach for determination of all rate constants involved in the interconversion
Authors: Dubský Pavel , Tesařová Eva , Gaš Bohuslav 
Published: February 2004

AbstractWhen enantiomers separated by chromatography or capillary electrophoresis undergo interconversion reaction (enantiomerization) during the separation, it leads to a typical detection pattern: two individual peaks of the separated enantiomers are connected with a plateau consisting of a mixture of both separated enantiomers. We propose a separation method for determination of all individual rate constants (or inversion barriers) of the interconversion. The method enables to distinguish which part of interconversion takes place in the free (unbound) form of the analyte and which part in the complexed (bound) form. Further, we propose a complete dynamic model of capillary electrophoresis of interconverting enantiomers based on solving a complete set of continuity equations for all constituents of the separation system together with complexation and acid‐base equilibria. This allows a simulation of both linear and nonlinear mode of separation and understanding all processes taking place in such enantioseparation systems. We demonstrate the applicability of the method on determination of the rate constants of interconversion of oxazepam enantiomers separated in systems with charged cyclodextrin chiral selectors.
Capillary electrochromatographic analysis of barbiturates in serum
Authors: Ohyama Kaname , Wada Mitsuhiro , Lord Gwyn A. , Ohba Yoshihito , Fujishita Osamu , Nakashima Kenichiro , Lim Chang Kee , Kuroda Naotaka 
Published: February 2004

AbstractA capillary electrochromatographic method was developed for the separation of barbiturates. The separation was optimized in a 75 μm ID capillary, packed with 3‐(1,8‐naphthalimido)propyl‐modified silyl silica gel (NAIP), studying the effect of buffer pH, buffer concentration, and mobile phase composition. Using an applied voltage of 20 kV and the short‐end injection method (9 cm capillary effective length), the mobile phase of 1.0 mM citrate buffer (pH 5.0) containing 40% methanol provided the baseline separation of barbital, phenobarbital, secobarbital, and thiopental (internal standard) in less than 4.5 min. The method was successfully applied to the analysis of barbiturates in human serum. Under the optimal conditions, good repeatability and linearity were obtained in the range of 2.90–43.29 μg/mL for barbital, phenobarbital, and secobarbital.
Separation of phenylthiohydantoin amino acids by capillary electrochromatography
Authors: Mueller Thomas , Posch Ulrike C. , Lindner Herbert H. 
Published: February 2004

AbstractCapillary electrochromatography (CEC) was employed as a rapid and high‐efficiency method for the isocratic separation of all 20 important phenylthiohydantoin (PTH) amino acids, the end products of Edman degradation during N‐terminal protein sequencing. For this purpose, 75 μm ID fused‐silica capillaries were packed with standard 3 μm Hypersil octadecyl silica (ODS) particles using a two‐step column fabrication process, which represents a fast, reliable and efficient means of producing long‐term stable columns. The influence of solvent composition, pH, type of buffer cation, buffer concentration, and temperature on retention behavior of PTH amino acids was investigated. Same‐day and day‐to‐day reproducibility of the retention times (over a period of two months) were found to be better than 3%. When comparing this new technique with traditional reversed phase‐high performance liquid chromatography (RP‐HPLC) methods applied in automated protein sequenators, CEC shows essentially shorter separation times and superior resolution.
Novel anionic copolymerized surfactants of mixed achiral and chiral surfactants as pseudostationary phases for micellar electrokinetic chromatography
Authors: Akbay Cevdet , Tarus Jepkoech , Gill Nicole L. , Agbaria Rezik A. , Warner Isiah M. 
Published: February 2004

AbstractOne disadvantage of amino acid‐based chiral selectors for micellar electrokinetic chromatography (MEKC) is that either they have very low solubility or are insoluble at acidic pHs. In order to increase solubilities at lower pHs, we have synthesized a highly water‐soluble achiral surfactant and copolymerized it with an amino acid‐based chiral surfactant. These two surfactants were polymerized either separately or at various molar rations of binary solutions, yielding pure molecular or copolymerized surfactant (CoPS), respectively. All surfactants were characterized by use of several analytical techniques prior to using them as novel pseudostationary phases in MEKC. The chromatographic performance of the CoPS in MEKC was tested with chiral and achiral analytes. The highly soluble sulfate head group significantly increased the solubility of amino acid‐based CoPS over a wide range of pH. Three chiral binaphthyl derivatives were tested and each surfactant system was found to have different selectivity.
Open‐tubular capillary electrochromatography/electrospray ionization‐mass spectrometry using polymeric surfactant as a stationary phase coating
Authors: Zhu Xiaofeng , Kamande Mary W. , Thiam Serigne , Kapnissi Constantina P. , Mwongela Simon M. , Warner Isiah M. 
Published: February 2004

AbstractWe describe the use of the polymeric surfactant poly(sodium undecylenic sulfate) (poly‐SUS) as a stationary phase coating in open‐tubular capillary electrochromatog raphy (OT‐CEC) coupled with electrospray ionization‐mass spectrometry (ESI‐MS) for the analysis of β‐blocker and benzodiazepine analytes. The production of a polymeric surfactant coating on the capillary inner wall involves (i) adsorption of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) to the inner surface of capillary, and (ii) adsorption of the negatively charged poly‐SUS onto the cationic polymer layer via strong physical interaction of the two polymer layers. As compared with micellar electrokinetic chromatography (MEKC) coupled with ESI‐MS, the main advantage of this proposed method is minimization of introduction of the monomeric or polymeric surfactant into the mass spectrometer, thus avoiding the interference of the nonvolatile micelle in ESI‐MS. The effects of buffer pH and applied voltage on the separation of the analytes are also discussed. Under optimum conditions, four of the five β‐blockers and four benzodiazepines are separated.
Combination of cyclodextrins and polymeric surfactants for chiral separations
Authors: Valle Bertha C. , Billiot Fereshteh H. , Shamsi Shahab A. , Zhu Xiaofeng , Powe Aleeta M. , Warner Isiah M. 
Published: February 2004

AbstractA cyclodextrin‐modified micellar electrokinetic chromatography (CD‐MEKC) method was applied to the enantioseparation of three binaphthyl derivatives using neutral CDs (i.e., β‐ and γ‐CD) in combination with various chiral amino acid‐based polymeric surfactants (PSs). Both the D‐ and L‐configurations of poly(sodium N‐undecanoyl alaninate), poly(sodium N‐undecanoyl leucinate), and poly(sodium N‐undecanoyl valinate) (poly(L‐SUV)) were synthesized. The retention behavior of the three binaphthyl derivatives under optimum electrophoretic conditions using a single chiral additive (PS or CD) is discussed. In addition, the effect of CD cavity size and stereochemical configuration of polymeric surfactants on selectivity (α) and resolution (Rs) was investigated. The enantioseparation of (±)1,1'‐binaphthyl‐2,2'‐diamine gave a reversal of enantiomeric order when using β‐CD in combination with any of the three D‐configuration PS. However, better enantioseparation is obtained when using the corresponding L‐configuration PS with β‐CD. A reversal of migration order (RMO) for the enantiomers of (±)1,1'‐bi‐2‐naphthol was observed upon the addition of 10 mM γ‐CD to poly(L‐SUV). However, no RMO of (±)1,1'‐bi‐2‐naphthol was seen when either β‐CD or γ‐CD was combined with D‐PS. The enantiomers of (±)1,1'‐binaphthyl‐2,2'‐diyl hydrogen phosphate showed little enantioselective behavior toward the PS alone. However, combined D‐ or L‐PS and β‐CD or γ‐CD systems gave increased Rs and α values. The chiral recognition of binaphthyl derivatives observed resulting from the various combinations of two chiral selectors is discussed.
Recent advances in the study of biomolecular interactions by capillary electrophoresis
Authors: He Xinya , Ding Yongsheng , Li Dazhi , Lin Bingcheng 
Published: February 2004

AbstractCapillary electrophoresis (CE) has been abundantly used in the study of molecular interactions owing to such advantages as short analysis time, low sample size requirement, high separation efficiency, and flexible applications. The focus of this paper is to review recent studies and advances (mainly from 1998 to now) in biomolecular interactions using CE. Five CE modes: zone migration CE, affinity CE, frontal analysis (FA), Hummel‐Dreyer (HD) and vacancy peak (VP) are cited and compared. Quantitative aspects of the thermodynamics and kinetics of biomolecular interaction are reviewed. Several biomolecular binding systems, including protein‐protein (polypeptide), protein‐DNA (RNA), protein(polypeptide)‐carbohydrate, protein‐small molecule, DNA‐small molecule, small molecule‐small molecule, have been well characterized by CE. CE is shown to be a powerful tool for the determination of the binding parameters of various bioaffinity interactions.
Analysis of ephedra‐alkaloids using sweeping and cation‐selective exhaustive injection and sweeping micellar electrokinetic chromatography methods
Authors: Chiang Hui‐Yu , Sheu Shuenn‐Jyi 
Published: February 2004

AbstractTwo stacking methods of capillary electrophoresis (CE) were developed for the separation of very dilute solutions of ephedra‐alkaloids, namely ephedrine, pseudoephedrine, methylephedrine, methylpseudoephedrine, norephedrine, and norpseudoephedrine. A sweeping method which uses a carrier comprised of phosphoric acid, sodium dodecyl sulfate (SDS), diethylamine and acetonitrile permits the detection of the alkaloids down to the 10−1 μg/mL level, and the cation‐selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI‐Sweep‐MEKC) method using phosphoric acid, SDS, and acetronitrile as electrolytes can detect down to the 10−3 μg/mL level. The former requires the conductance of the sample solution to be adjusted beforehand, and only five peaks were observed, two of which were overlapped. The latter is capable of separating the six alkaloids but has a somewhat poorer reproducibility. Using an optimized injection time, it was found that the more diluted a solution is, the greater the sweeping effect will be. The CSEI‐Sweep‐MEKC method with a 600 s injection time and a 10−1 μg/mL solution concentration provides an amplification effect of ∼ 104. The method is suitable for analyses of dilute herb drug extracts and mouse sera. The effect of buffers on the separation and validation of the methods in this study are also discussed.
Development and validation of a robust capillary electrophoresis method for impurity profiling of calcium levofolinate including the (6R,2'S)‐diastereomer using statistical experimental design
Authors: Süß Falko , Harang Valérie , Sänger‐van de Griend Cari E. , Scriba Gerhard K. E. 
Published: February 2004

AbstractA chiral capillary electrophoresis assay for the simultaneous determination of the optical purity and of related substances of calcium levofolinate has been developed and validated. Using 2,6‐dimethyl‐β‐cyclodextrin as chiral selector at a concentration of 20 mg/mL, the method was optimized using a full factorial design with four factors including pH and concentration of the background electrolyte, column temperature and separation voltage. Optimized conditions were a 40 mM sodium tetraborate buffer, pH 9.9, a capillary temperature of 16°C, and an applied voltage of 21 kV. Methotrexate was used as internal standard to compensate for injection errors and fluctuations of the migration times. A multiple linear regression model was also used to test the robustness of the method. Validation was performed with respect to specificity, linearity, range, limit of quantification and detection, precision, and accuracy. The assay allowed the detection and determination of related substances including the diastereomeric (6R,2'S)‐impurity of levofolinic acid at the 0.1% level, the identification threshold of impurities for orally administered drugs for human use defined by the International Conference on Harmonization guidelines as well as the European Pharmacopoeia.
Preparation and evaluation of molecularly imprinted polymers based on 9‐ethyladenine for the recognition of nucleotide bases in capillary electrochromatography
Authors: Huang Yi‐Chen , Lin Chun‐Chi , Liu Chuen‐Ying 
Published: February 2004

AbstractA molecularly imprinted polymer (MIP) comprising 9‐ethyladenine was polymerized in situ inside the capillary for the electrochromatographic separation of nucleotide bases. The capillary wall was first functionalized with 3‐trimethoxysilylpropyl methacrylate (10% v/v) and 1,1‐diphenyl‐2‐picrylhydrazyl (0.01% w/v) in toluene. Following this treatment, the capillary was filled with acetonitrile containing 9‐ethyladenine, methacrylic acid, ethylene glycol dimethacrylate, and initiator. After polymerization, the MIP was shrunk into a film against the inner wall of the capillary with the syringe pump. The template was then removed with methanol under nitrogen flow. For evaluation the feasibility of the MIP column for the separation of nucleotide bases, some parameters including the pH, concentration of the background electrolyte, the applied voltage as well as the effect of organic modifier were studied. The migration behavior of nucleotide bases on the MIP column was also compared with that on the bare fused‐silica column. The results indicated that the MIP columns demonstrated better recognition properties at a pH range of 6–8. The efficiency (plates/m) at pH 8 for the nonimprinted analyte was 75 300 for cytosine, 50 200 for thymine, and 14 800 for guanine. However, the efficiency for the imprinted analyte, adenine, was quite low. This was evidenced by the broad peak, yielding only 2600 plates/m.
Effect of oil substitution in chiral microemulsion electrokinetic chromatography
Authors: Mertzman Melissa D. , Foley Joe P. 
Published: February 2004

AbstractIn a previous publication (Pascoe, R., Foley, J. P., Analyst 2002, 127, 710–714 [1]), a novel chiral microemulsion based on 1.0% w/v dodecoxycarbonylvaline (DDCV), 0.50% v/v ethyl acetate and 1.2% v/v 1‐butanol, was shown to provide rapid enantiomeric separations of various pharmaceutical compounds. The two deficiencies noted with this method were that the peak shapes obtained were asymmetric and the efficiencies were lower than those previously obtained using DDCV micelles (Peterson, A. G., Ahuja, E. S., Foley, J. P., J. Chromatogr. B 1996, 683, 15–28 [2]). This study examines the use of three alternative low‐interfacial‐tension oils (methyl acetate, methyl propionate, and methyl formate), in combination with DDCV, to characterize their effect on the elution range, efficiency, resolution, and enantioselectivity of various pharmaceutical enantiomers. The oils were evaluated in both the same volume percentage and the same molar concentration as ethyl acetate in the original DDCV microemulsion system. Including ethyl acetate, a total of seven microemulsion systems were examined. For the compounds that were separated, average enantioselectivities ranged from 1.09 to 1.28, with corresponding efficiencies of 14 000–20 000. While some interesting differences were observed, ethyl acetate still proved to be the most advantageous in terms of enantioselectivity, resolution, and elution range.