Home About us Contact
|
Home About us Contact | ||
|
|
||
Simultaneous Separation (simultaneous + separation)
Selected AbstractsSimultaneous separation of fifteen approved protease and reverse transcriptase inhibitors for human immunodeficiency virus therapy by capillary electrophoresisELECTROPHORESIS, Issue 4 2003Nguyen Duc Tuan Abstract In the present investigation, a novel approach towards a complete separation of all 15 protease and reverse transcriptase inhibitors which are currently approved for use in highly active antiretroviral therapy in a single analytical run is presented. The developed method employs an acidic background electrolyte with sodium polyanethol sulfonate (SPAS) as polyanionic electroosmotic flow (EOF) modifier to establish a strong cathodic EOF, sodium dodecyl sulfate (SDS) as pseudostationary selector, and acetonitrile and ethanol as organic modifiers. Separation of the analytes is based on two different mechanisms. The more basic analytes are protonated at the prevailing pH conditions and thus migrate in front of the cathodic EOF, whereas the less basic and neutral analytes interact with the SDS and are retained after the EOF. By optimizing electrolyte pH, the amount of solvents and SDS concentrations in the background electrolyte it is possible to completely separate all compounds of interest. [source] Simultaneous separation and identification of oligomeric procyanidins and anthocyanin-derived pigments in raw red wine by HPLC-UV-ESI-MSnJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2006S. Pati Abstract Samples of raw red wine (Primitivo di Manduria, Apulia, Southern Italy) were analysed without any pre-treatment (except 1 : 2 dilution with water) using HPLC with detection based on UV absorbance and Electrospray Ionisation Sequential Mass Spectrometry (ESI-MSn, with n = 1,3) in a series configuration. In particular, absorbance at 520 nm was monitored for UV detection in order to identify pigments responsible for wine colour. On the other hand, two subsequent stages of MS detection based on positive ions were adopted. The first consisted of an explorative MS acquisition, aimed at the individuation of the m/z ratios for positively charged compounds; the second was based on fragmentation of the detected ions within an ion trap analyser, followed by MS/MS and, if required, MS3 acquisitions. The synergy between UV detection and MSn analysis led to the identification of 41 pigments, which can be classified into five groups: grape anthocyanins, pyranoanthocyanins, vinyl-linked anthocyanin-flavanol pigments, ethyl-bridged anthocyanin-flavanol pigments and flavanol-anthocyanin compounds. Many isomeric and oligomeric structures were found within each group. A further class of compounds, not absorbing in the visible spectrum, could be also characterised by ESI-MSn and corresponded to B-type procyanidins, i.e. proanthocyanidins arising from C4,C8/C4,C6 couplings between catechin or epicatechin units. In particular, oligomeric structures (from dimers to pentamers), often present with several isomers, were identified and their fragmentation patterns clarified. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous separation of intracellular and extracellular lactate NMR signals of human erythrocytesMAGNETIC RESONANCE IN MEDICINE, Issue 2 2007Götz Kohler Abstract Intracellular/extracellular lactate (Lac) distribution has been determined before in human and animal erythrocytes (red blood cells [RBCs]) with various methods. However, all previous methods determine intra- and extracellular Lac separately or indirectly. Now, 13C-NMR spectroscopy has been used to monitor intra- and extracellular Lac simultaneously in intact RBCs. Isolated human RBCs were incubated with [3- 13C]-Lac, [3- 13C]-pyruvate (Pyr), and [1- 13C]-glucose (Gluc). A distortionless enhancement by polarization transfer (DEPT) sequence was used (TR = 3.3 s, N = 128) to monitor the 13C-NMR resonances in both compartments. The intra- and extracellular methyl group resonances of Lac and Pyr were clearly separated by 9.6 Hz and 7.0 Hz, respectively, under normoxic conditions due to the RBC chemical-shift effect. The results show that the chemical-shift effect of RBCs is convenient to monitor intra- and extracellular Lac simultaneously in intact RBCs under normoxic conditions. Magn Reson Med 58:213,217, 2007. © 2007 Wiley-Liss, Inc. [source] Separation of cytokinin isomers with a partial filling-micellar electrokinetic chromatography-mass spectrometry approachELECTROPHORESIS, Issue 10 2008Liya Ge Abstract A new method based on partial filling-MEKC (PF-MEKC) directly coupled to ESI-MS was developed for the simultaneous separation and determination of 13 structurally similar cytokinins, including various geometric and positional isomers of cytokinins. On the basis of the resolution of the neighboring isomer peaks, different parameters (i.e., pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation. Under optimum conditions, the separation of 13 cytokinin standards was accomplished within 25,min. MS/MS with multiple reaction monitoring detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed for the direct identification and confirmation of the cytokinins present in banana (Musa spp.) pulp sample after extraction and purification. Finally, trans- zeatin riboside (ZR) and trans- zeatin (Z) were unambiguously identified in banana pulp. It is anticipated that the current PF-MEKC-MS method can be applied to analyze cytokinins in a wide range of biological samples. [source] Determination of neutral carbohydrates by CZE with direct UV detectionELECTROPHORESIS, Issue 17 2007Stella Rovio Abstract A new CZE method relying on in-capillary reaction and direct UV detection at the wavelength 270,nm is presented for the simultaneous separation of the neutral carbohydrates xylitol, D -(,)-mannitol, sucrose, D -(+)-fucose, D -(+)-cellobiose, D -(+)-galactose, D -(+)-glucose, L -rhamnose, D -(+)-mannose, D -(,)-arabinose, D -(+)-xylose, and D -(,)-ribose. The alkaline electrolyte solution was prepared of 130,mM sodium hydroxide and 36,mM disodium hydrogen phosphate dihydrate. Separation of the sample mixture was achieved within 35,min. Calibration plots were linear in the range of 0.05,3,mM. Reproducibility of migration times was between 0.3 and 1.1%, and the detection limits for the analytes were 0.02 and 0.05,mM. The optimized method was applied for the determination of neutral monosaccharides in lemon, pineapple, and orange juices and a cognac sample. The methodology is fast since no other sample preparation except dilution is required. [source] Rapid detection of Staphylococcus aureus by a combination of monoclonal antibody-coated latex and capillary electrophoresisELECTROPHORESIS, Issue 9 2006Peng Gao Abstract The rapid detection of pathogenic bacteria is extremely important in biotechnology and clinical diagnosis. CE has been utilized in the field of bacterial analysis for many years, but to some extent, simultaneous separation and identification of certain microbes from complex samples by CE coupled with UV detector is still a challenge. In this paper, we propose a new strategy for rapid separation and identification of Staphylococcus aureus (S.,aureus) in bacterial mixtures by means of specific mAb-coated latex coupled with CZE. An appropriate set of conditions that selectively isolated S.,aureus from the microorganisms Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae were established. S.,aureus could be differentiated from the others by unique peaks in the electropherograms. The validity was also confirmed by LIF with antibodies specific to both the latex and the microbial cells. The LOD is as low as 9.0×105 colony forming unit/mL. We have also utilized this technology to identify S.,aureus in a stool sample coming from a healthy volunteer spiked successfully with S.,aureus. This CZE-UV technique can be applied to rapid diagnosis of enteritis caused by S.,aureus or other bacterial control-related fields needing rapid identification of target pathogens from microbial mixtures. In theory, this method is suitable for the detection of any bacterium as long as corresponding bacterium-specific antibody-coated latex is available. [source] Analysis of oxycodol and noroxycodol stereoisomers in biological samples by capillary electrophoresisELECTROPHORESIS, Issue 10 2005Andrea Baldacci Abstract A capillary electrophoresis (CE) method for the separation of the diastereoisomers of 6-oxycodol (6OCOL) and nor-6-oxycodol (N6OCOL), the 6-keto-reduced metabolites of oxycodone (OCOD) and noroxycodone (NOCOD), respectively, is reported and employed to assess the stereoselectivity of these metabolic steps in vivo, in vitro, and in chemical synthesis. CE in an untreated fused-silica capillary with acidic buffers containing 2-hydroxypropyl-,-cyclodextrin, randomly sulfated ,-cyclodextrin, or single isomer heptakis(2,3-diacetyl-6-sulfato)-,-cyclodextrin (HDAS-,-CD) is shown to permit the simultaneous separation of the stereoisomers of 6OCOL and N6OCOL. A 100 mM phosphate buffer of pH 2.0 containing 2.05% w/v HDAS-,-CD provides a medium for rapid analysis and unambiguous identification of these stereoisomers in solid-phase extracts of (i) urines stemming from patients under pharmacotherapy with OCOD, (ii) incubations of OCOD and NOCOD with human liver cytosol and the human liver S9 fraction, and (iii) after chemical synthesis from OCOD and NOCOD using NaBH4. In all cases, ,-N6OCOL is shown to be the predominant stereoisomer of N6OCOL. For 6OCOL, the same is true for in vitro formation and for chemical synthesis. In urine, however, ,-6OCOL is observed to be excreted in a higher amount than ,-6OCOL. For the urinary ,-/,-isomer ratio of 6OCOL and N6OCOL, there are no differences between the data obtained for nonhydrolyzed and enzymatically hydrolyzed urines. The data document the stereoselectivity of the 6-keto-reduction of OCOD and NOCOD in man. [source] Polymeric alkenoxy amino acid surfactants: II.,Chiral separations of ,-blockers with multiple stereogenic centersELECTROPHORESIS, Issue 6 2004Syed A. A. Rizvi Abstract Two amino acid-based (leucine and isoleucine) alkenoxy micelle polymers were employed in this study for the separation of multichiral center-bearing ,-blockers, nadolol and labetalol. These polymers include polysodium N -undecenoxy carbonyl- L -leucinate (poly- L -SUCL) and polysodium N -undecenoxy carbonyl- L -isoleucinate (poly- L -SUCIL). Detailed synthesis and characterization were reported in our previous paper [26]. It was found that poly- L -SUCIL gives better chiral separation than poly- L -SUCL for both nadolol and labetalol isomers. The use of 50,100 mM poly- L -SUCIL as a single chiral selector provided separation of four and three isomers of labetalol and nadolol, respectively. Further optimization in separation of both enantiomeric pairs of nadolol and labetalol was achieved by evaluation of type and concentration of organic solvents, capillary temperature as well type and concentration of cyclodextrins. A synergistic approach, using a combination of poly- L -SUCIL and sulfated ,-CD (S-,-CD) was evaluated and it showed dramatic separation for enantiomeric pairs of nadolol. On the other hand for labetalol enantiomers, separation was slightly decreased or remain unaffected using the dual chiral selector system. Finally, simultaneous separation of both nadolol and labetalol enantiomers was achieved in a single run using 25 mM poly- L -SUCIL and 5% w/v of S-,-CD in less then 35 min highlighting the importance of high-throughput chiral analysis. [source] Polymeric alkenoxy amino acid surfactants: I. Highly selective class of molecular micelles for chiral separation of ,-blockersELECTROPHORESIS, Issue 15 2003Syed A. A. Rizvi Abstract Two amino acid-based alkenoxy micelle polymers were synthesized for this study. These include polysodium N -undecenoxy carbonyl- L -leucinate (poly- L -SUCL) and polysodium N -undecenoxy carbonyl- L -isoleucinate (poly- L -SUCIL). The polymerization time and concentration of the synthesized micelle polymers were optimized by 1H-nuclear magnetic resonance (NMR) and capillary electrophoresis (CE) experiments. Detailed physicochemical properties (1H NMR, critical micelle concentration (CMC), optical rotation, partial specific volume, aggregation number, and polarity) were determined, and these molecular micelles were introduced as a pseudostationary phase in micellar electrokinetic chromatography to study the molecular recognition and to develop a method for simultaneous separation of eight chiral ,-blockers. It is found that poly- L -SUCL gives overall better chiral resolution and wider chiral window than poly- L -SUCIL. After optimizing the type of micelle polymer, injection size and temperature, simultaneous separation and enantioseparation of eight ,-blockers were achieved in less than 35 min. A comparison with the amide-type surfactants of the same polar head group and alkyl chain length showed that carbamate-type surfactants always work better than the corresponding amide-type surfactant. [source] Derivatization of inorganic ions in capillary electrophoresisELECTROPHORESIS, Issue 12-13 2003Audrius PadarauskasArticle first published online: 8 JUL 200 Abstract This review gives a short overview of the main approaches to the derivatization of inorganic ions in capillary electrophoresis (CE) with emphasis on the most recent works. Various derivatization procedures and detection methods are discussed. A brief account of their advantages and limitations is given. More specific areas such as microchip CE, simultaneous separation of anions and cations, and speciation analysis are also briefly discussed. [source] Preparative separation of a multicomponent peptide mixture by mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006Xinli Yang Abstract We report on the first multiplex preparative separation by mass spectrometry of bio-organic molecules in the 200,350 Da mass range that is typical for synthetic drugs. A five-component mixture consisting of two di- and three tripeptides has been separated by mass using a specially designed mass spectrometer. The instrument for preparative separations consists of an electrospray ionization (ESI) source, ion transfer optics, an electrostatic sector, and an inhomogeneous-field magnetic mass analyzer that achieves linear mass dispersion of ion beams. Protonated peptides produced by electrospray were separated, nondestructively landed on a 16-channel array of dry collector plates, and reconstituted in solution. The preparation procedures and the instrumental conditions have been optimized to maximize the ion currents. The significant features of the special mass spectrometer are high ion currents and simultaneous separation and collection of mixture components. Copyright © 2006 John Wiley & Sons, Ltd. [source] Monolithic poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for simultaneous separation of low- and high-molecular-weight compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Andreas Greiderer Abstract Monolithic poly(1,2-bis(p -vinylphenyl)ethane (BVPE)) capillary columns were prepared by thermally initiated free radical polymerisation of 1,2-bis(p -vinylphenyl)ethane in the presence of inert diluents (porogens) and ,,,,-azoisobutyronitrile (AIBN) as initiator. Polymerisations were accomplished in 200 ,m ID fused silica capillaries at 65°C and for 60 min. Mercury intrusion porosimetry measurements of the polymeric RP support showed a broad bimodal pore-size-distribution of mesopores and small macropores in the range of 5,400 nm and flow-channels in the ,m range. N2 -adsorption (BET) analysis resulted in a tremendous enhancement of surface area (101 m2/g) of BVPE stationary phases compared to typical organic monoliths (,20 m2/g), indicating the presence of a considerable amount of mesopores. Consequently, the adequate proportion of both meso- and (small) macropores allowed the rapid and high-resolution separation of low-molecular-weight compounds as well as biomolecules on the same monolithic support. At the same time, the high fraction of flow-channels provided enhanced column permeability. The chromatographic performance of poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for the separation of biomolecules (proteins, oligonucleotides) and small molecules (alkyl benzenes, phenols, phenons) are demonstrated in this article. Additionally, pressure drop versus flow rate measurements of novel poly(1,2-bis(p -vinylphenyl)ethane) capillary columns confirmed high mechanical robustness, low swelling in organic solvents and high permeability. Due to the simplicity of monolith fabrication, comprehensive studies of the retention and separation behaviour of monolithic BVPE columns resulted in high run-to-run and batch-to-batch reproducibilities. All these attributes prove the excellent applicability of monolithic poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for ,-HPLC towards a huge range of analytes of different chemistries and molecular sizes. [source] Quantitative separation of oxytocin, norfloxacin and diclofenac sodium in milk samples using capillary electrophoresisBIOMEDICAL CHROMATOGRAPHY, Issue 9 2009Amber R. Solangi Abstract A simple, sensitive and rapid method has been developed for simultaneous separation and quantification of three different drugs: oxytocin (OT), norfloxacin (NOR) and diclofenac (DIC) sodium in milk samples using capillary electrophoresis (CE) with UV detection at 220 nm. Factors affecting the separation were pH, concentration of buffer and applied voltage. Separation was obtained in less than 9 min with sodium tetraborate buffer of pH 10.0 and applied voltage 30 kV. The separation was carried out from uncoated fused silica capillary with effective length of 50 cm with 75 µm i.d. The carrier electrolyte gave reproducible separation with calibration plots linear over 0.15,4.0 µg/mL for OT, 5,1000 µg/mL for NOR and 3,125 µg/mL for DIC. The lower limits of detection (LOD) were found to be 50 ng/mL for OT, and 1 µg/mL for NOR and DIC. The method was validated for the analysis of drugs in milk samples and pharmaceutical preparations with recovery of drugs within the range 96,100% with RSD 0.9,2.8%. Copyright © 2009 John Wiley & Sons, Ltd. [source] Analysis of optical purity and impurity of synthetic d -phenylalanine products using sulfated ,-cyclodextrin as chiral selector by reversed-polarity capillary electrophoresisCHIRALITY, Issue 2 2006Yan Zhao Abstract A new capillary electrophoresis (CE) method has been achieved for simultaneous separation and quantification of phenylalanine, N -acetylphenylalanine enantiomers, and prochiral N -acetylaminocinnamic acid, possibly co-existent in reaction systems or synthesized products of d -phenylalanine. The separation was carried out in an uncoated capillary under reversed-electrophoretic mode. Among the diverse charged cyclodextrins (CDs) examined, highly sulfated (HS)-,-CD as the chiral selector exhibited the best enantioselectivity. The complete separation of the analytes was obtained under the optimum conditions of pH 2.5, 35 mM Tris buffer containing 4% HS-,-CD, applied voltage ,15 kV, and capillary temperature 25°C. Furthermore, the proposed method was applied to the determination of optical purity and trace impurities in three batches of the asymmetric synthetic samples of d -phenylalanine, and satisfactory results were obtained. The determination recoveries of the samples were in the range of 97.8,103.8%, and precisions fell within 2.3,5.0% (RSD). The results demonstrate that this CE method is a useful, simple technique and is applicable to purity assays of d -phenylalanine. © 2005 Wiley-Liss, Inc. Chirality 18:84,90, 2006. [source] Miniaturized movable contactless conductivity detection cell for capillary electrophoresisELECTROPHORESIS, Issue 12-13 2003Miroslav Macka Abstract A miniaturized capacitively coupled contactless conductivity detector (mini-C4D) cell has been designed which is small enough to allow it to slide along the effective capillary length inside the capillary cassette of an Agilent capiillary electrophoresis system (CE) (or other CE brand of similar construction), including the possibility of positioning it close to the point of optical detection (4 cm), or even putting two such detector cells in one cassette. The cell was tested and the performance characteristics (noise, sensitivity, and peak width) were compared with those obtained with the previously used large C4D cell. No significant differences were observed. The mini-C4D was used in simultaneous separations of common cations and anions where its advantage over a larger C4D cell is the ability to vary the point of detection with the mini-C4D cell continuously at any point along the capillary length, so that the optimum apparent selectivity can be chosen. Other applications include providing a convenient second point of detection in addition to photometric detection, such as to measure accurately the linear velocity of a zone, or to allow placement of two mini-C4D cells in one capillary cassette simultaneously. [source] Generic separations and leaf languagesMLQ- MATHEMATICAL LOGIC QUARTERLY, Issue 4 2003Matthias Galota Abstract In the early nineties of the previous century, leaf languages were introduced as a means for the uniform characterization of many complexity classes, mainly in the range between P (polynomial time) and PSPACE (polynomial space). It was shown that the separability of two complexity classes can be reduced to a combinatorial property of the corresponding defining leaf languages. In the present paper, it is shown that every separation obtained in this way holds for every generic oracle in the sense of Blum and Impagliazzo. We obtain several consequences of this result, regarding, e. g., universal oracles, simultaneous separations and type-2 complexity. [source] | ||||||||||