Search results for "Elution"
showing 10 items of 337 documents
Influence of oscillating main flow on separation efficiency in asymmetrical flow field-flow fractionation.
2021
The steadily rising interest in the investigation of interactions between nanomaterials and biological media has also led to an increasing interest in asymmetrical flow field-flow fractionation (AF-FFF). The biggest strength of AF-FFF is the possibility to alter the flow profiles to suit a specific separation problem. In this paper, the influence of an oscillating main flow on the separation efficiency of AF-FFF is investigated. Such oscillations can e.g. be caused by the main pump To investigate the influence of such flow conditions on the separation efficiency in AF-FFF systematically, different oscillation profiles were applied and their influence on the elution profile and the retention…
Ein automatisches viskosimeter zur flüssigkeitschromatographie
1968
Eine Viskosimeterapparatur wird beschrieben, die ein automatisches sukzessives Einfullen und Meessen von Flussigkeiten erlaubt. Bei chromatographischen Prozessen ermoglicht es das Gerat, auser der bisher ublichen Verfolgung der Konzentration auch das Molekulargewicht des gelosten Stoffes im Eluat zu bestimmen. Fur eine Elutionsgeschwindigkeit von 1 ml/min ist es moglich, das mittlere viskosimetrische Molekulargewicht in Intervallen von jeweils 2 ml oder auch 1 ml fur den gesamten Elutionsvorgang anzugeben. A viscometer system is described, which allows automatic successive loading and measuring of liquids. For chromatographic columns the apparatus can registrate not only the concentration b…
Gelchromatographische refraktionierung, 1. Ein verfahren zur korrektur von gelchromatogrammen
1979
A mathematical method is proposed for calculating the gel chromatogram w(v0) after correction with the instrument spreading function D(v, v0) and for calculating D(v,v0) using experimental data on the basis, that a gel chromatographic polymer fraction of the chromatogram e(v) is collected and injected again. The chromatogram of this fraction c(v) can be described by the integral equation: where v0 is the elution volume and v1 is the volume at which the fraction is collected. The solution of this equation simultaneously with Tung's equation by way of minimizing is suggested.
High-performance liquid chromatographic enantiomer separation and determination of absolute configurations of phosphinic acid analogues of dipeptides…
2003
The enantiomers of N-benzyloxycarbonyl-phosphinic pseudodipeptides and their N-benzyloxycarbonyl-α-aminophosphinic acid precursors as well as various other structural analogues were separated on a set of cinchona alkaloid-derived chiral anion-exchangers by HPLC in the reversed-phase mode. Semi-preparative scale chromatography provided single enantiomers in 100 mg quantities. The configurations of the enantiomers were assigned indirectly by enantioselective chromatography on the basis of the elution order and was confirmed by enantiomeric reference compounds.
Lignans from Torreya jackii identified by stopped-flow high-performance liquid chromatography–nuclear magnetic resonance spectroscopy
1999
Abstract Coupled reversed-phase HPLC–NMR spectroscopy has been applied to the rapid detection and identification of plant metabolites of Torreya jackii , a species of Taxaceae. Analysis consisted of gradient HPLC elution and directly coupled 1 H NMR (500 MHz) spectroscopic detection in a stopped-flow mode. Seven lignans were detected and their structures were elucidated, based on their HPLC– 1 H NMR spectra and MS data. The structures were confirmed by isolation of the single components followed by conventional NMR measurements.
Keyhole limpet hemocyanin (KLH), I: Reassociation from Immucothel® followed by separation of KLH1 and KLH2
1997
Abstract Studies of keyhole limpet hemocyanin (KLH) normally require purification of functional complexes directly from living animals. An alternative procedure is described wherein a commercial preparation of KLH which is fully dissociated into its subunits (Immucothel®, biosyn Arzneimittel GmbH) is reassociated in the presence of a high concentration of calcium and magnesium. The reassociation products, when observed by electron microscopy, consist of didecamers, multidecamers and flexible tubules of varying length. The two forms of KLH described previously and designated KLH1 and KLH2, are present in the reassocated mixture as homo-oligomers/polymers and can be separated by selective dis…
High Submicellar Liquid Chromatography
2013
Surfactant addition above the critical micellar concentration (CMC), in reversed-phase liquid chromatography (RPLC), was proposed as a way to modify the selectivity and analysis time, giving rise to a chromatographic mode called micellar liquid chromatography (MLC). However, solutions containing only surfactant are too weak and yield poor peak shape. This was remediated by the addition of a small amount of organic solvent. To preserve the existence of micelles, in MLC high contents of organic solvent are avoided. Nevertheless, there is no reason to neglect the potentiality of mobile phases containing a surfactant above its CMC in water and a high organic solvent content (without micelles). …
Description of the Retention and Peak Profile for Chromolith Columns in Isocratic and Gradient Elution Using Mobile Phase Composition and Flow Rate a…
2014
The effect of the modifier concentration and flow rate on the chromatographic performance of a second generation Chromolith® RP-18e column, under isocratic and gradient elution with acetonitrile-water mixtures, was examined using four sulphonamides as probe compounds. The acetonitrile concentration was varied between 5 and 55% (v/v), and the flow rate between 0.1 and 5.0 mL/min, keeping the other factors constant. The changes in both retention and peak profile were modelled, and used to build simple plots, where the logarithm of the retention factor was represented against the modifier concentration (in gradient elution, against the initial modifier concentration), and the half-widths or wi…
Development of the H-point standard additions method for coupled liquid chromatography and UV-visible spectrophotometry
1992
Abstract This work establishes the fundamentals of the H-point standard additions method for liquid chromatography for the simultaneous analysis of binary mixtures with overlapped chromatographic peaks. The method was compared with the deconvolution method of peak suppression and the second derivative of elution profiles. Different mixtures of diuretics were satisfactorily resolved.
Gas—liquid chromatographic analyses
1985
Abstract The gas chromatographic retention behaviour of methylethyl, 1-methylpropyl, 2-methylpropyl, 1,2-dimethylpropyl, 1-methylbutyl and 3-methylbutyl esters of benzoic and o-, m- and p-chlorobenzoic acids on low-polarity (SE-30) and polar (OV-351) capillary columns under several temperature-programmed and isothermal conditions is reported. The retention data and the Kovats retention indices for all 24 components are given and the separation of a complex mixture is discussed. The retention index increments have been used to examine the effects of chain branching and chlorine substitution. The results are compared with those for n-alkyl benzoates and monochlorobenzoates.