Uncoated Capillary (uncoated + capillary)

Distribution by Scientific Domains

Selected Abstracts

Gas chromatographic retention in uncoated fused silica capillaries

Matthew S. Klee
Abstract Understanding of retention in uncoated fused-silica capillaries is of interest due to increased attention on precolumn backflushing in capillary GC. Uncoated capillaries offer several advantages as precolumns compared to coated precolumns. In order to examine the possibility of predicting elution temperatures of alkanes from uncoated capillaries a priori, several sizes of deactivated but uncoated fused-silica capillaries were evaluated under various operating conditions. Retention was found to depend on dimensionless ramp rate (°C/tM), sample loading (capacity), flow mode, and column dimensions (probably related to surface area). [source]

Novel negatively charged tentacle-type polymer coating for on-line preconcentration of proteins in CE

Liang Xu
Abstract A novel negatively charged tentacle-type polymer-coated capillary column was fabricated and applied for on-line extraction and preconcentration of proteins. The polymer coating was prepared by glycidyl-methacrylate graft polymerization in a silanized capillary column and the following sulfonic acid group functionalization. It had high surface area and offered high phase ratio for protein adsorption. In addition, the polymer-coated capillary column provided more stable EOF than a bare uncoated capillary. These features of the polymer coating facilitated the extraction of proteins through electrostatic interactions. This was used to extract proteins. The extracted analytes were then desorbed and focused by EOF in the direction opposite to the sample injection flow for subsequent CE. With this procedure, over 1500-fold sensitivity enhancement was realized for myoglobin (MB) as compared with a normal capillary zone electrophoresis. By comparison of the peak areas of the enriched protein, it was found that the polymer-coated column could capture proteins about 30 times more than the uncoated column. In addition, the separation of a protein mixture containing 0.4,,g/mL of MB and 0.4,,g/mL of insulin was demonstrated by the on-line preconcentration and electrophoretic separation with the polymer-coated column. [source]

Capillary electrophoresis of amphipathic ,-helical peptide diastereomers

Traian V. Popa
Abstract We have made a rigorous assessment of the ability of capillary electrophoresis to resolve peptide diastereomers through its application to the separation of a series of synthetic 18-residue, amphipathic ,-helical monomeric peptide analogues, where a single site in the centre of the hydrophobic face of the ,-helix is substituted by 19 L - or D -amino acids. Such L - and D -peptide pairs have the same mass-to-charge ratio, amino acid sequence and intrinsic hydrophobicity, varying only in the stereochemistry of one residue. CE approaches assessed in their ability to separate diastereomeric peptide pairs included capillary zone electrophoresis (uncoated capillary), micellar electrokinetic chromatography (uncoated capillary in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, CHAPS), open-tubular capillary electrochromatography (C8 -coated capillary in the presence of 25% 2,2,2-trifluoroethanol (TFE) or 25% ethanol). Overall, the OT-CEC methods were the most effective at separating the most peptide pairs, particularly for those containing hydrophilic side chains. However, the MEKC approach proved most effective for separation of peptide pairs containing hydrophobic or aromatic side chains. [source]

Poly(N -vinylimidazole)-grafted capillary for electrophoresis prepared by surface-initiated atom transfer radical polymerization

Jing Li
Abstract A CE method for poly(N -vinylimidazole) (PVI)-grafted capillaries by the surface-initiated atom transfer radical polymerization has been developed. The coating was prepared with N -vinylimidazole as the monomer, 2-bromo-2-methyl- N -[3-(triethoxysilyl) propyl] propanamide (BTPAm) as the initiator and CuCl/CuCl2/2,2,-bipyridine as the catalyst and ligand. The direction and magnitude of EOF in the PVI-grafted capillary were investigated in a pH range of 3.0,9.0. The results indicated that the EOF could be modulated by varying the pH value of the buffer and an anodic EOF was obtained at pH values below 6.5. A significant improvement in reproducibility and reduction of EOF appeared on the PVI-grafted capillary when compared with the uncoated capillary. Furthermore, the polymer coated capillaries were applied to the separations of the inorganic anions, organic acids and basic proteins and baseline separations were achieved with short analysis time and high reproducibility. [source]

Investigation of the separability of thaumatin by capillary electrophoresis

Milena Vespalcová
Abstract The electrophoretic behaviour of the highly basic protein thaumatin was explored in strongly acid (pH 2) and mildly acid (pH 4.5) separation systems using both bare and coated fused silica capillaries. The separation selectivity for thaumatin I, thaumatin II, and for other sample constituents was insufficient for their baseline separation at pH 2 in an uncoated capillary because the separation efficiency was markedly lower than is common in the electrophoretic separations of proteins. A separation selectivity higher by up to one order of magnitude has been reached at pH 4.5. A pronounced asymmetry of zones, which impaired resolution at this pH, was effectively suppressed by coating of the capillary wall with a polymer. In fact, adsorption on the capillary coating always plays a contributory role whenever a good separation of thaumatin constituents is attained. This indicates that electrochromatographic separation systems based on capillaries coated with the layer of either cationic or hydrophilic uncharged polymer hold promise for the development of methods for thaumatin analysis. [source]

Determination of trimebutine maleate in rat plasma and tissues by using capillary zone electrophoresis

Famei Li
A simple and rapid capillary zone electrophoresis method was developed for the determination of trimebutine maleate in rat plasma and tissues. Rat plasma and tissue homogenates were mixed with acetonitrile containing internal standard, ephedrine hydrochloride, and then centrifuged. The supernatant was dried under a stream of nitrogen, and the residue was reconstituted in methanol,water (1:1). The electrophoresis was performed in uncoated capillary with 30,mmol/L phosphate buffer of pH 6.0 as the separation electrolyte. The applied voltage was 10,kV and the UV detection was set at 214,nm. The peak height ratio vs concentration in plasma or homogenates was linear over the range of 5,500,ng/mL and the limit of quantitation was 5,ng/mL. The intra- and inter-day precision was RSD,<,14% and <15%. The accuracy was relative error (RE) within,±,14%. This method was applied to studying the pharmacokinetics and tissue distribution after a single dose of trimebutine maleate was administrated to the rats. The Tmax, AUC, Cmax and t1/2 were 30,min, 7.8,×,102 (ng/mL),min, 39,ng/mL and 1.7,×,102,min. The drug distribution was found in a decreasing order of liver, kidney, spleen, lung and heart. Copyright © 2001 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 electrophoresis

CHIRALITY, Issue 2 2006
Yan 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]