Search results for "SIZE-EXCLUSION CHROMATOGRAPHY"
showing 10 items of 137 documents
Prefractionation of aroma extracts from fat-containing food by high-performance size-exclusion chromatography
1996
A method for the prefractionation of aroma extracts of fat-containing food using high-performance size-exclusion chromatography is presented. The aim was to obtain a fraction of volatile compounds with a residual triglyceride content as low as possible, in order to allow its direct analysis by gas chromatography. Two different mobile phases, diethyl ether and dichloromethane, were tested and the elution volumes of triglycerides and a large variety of aroma compounds were measured. The quality of separation between triglycerides and volatile compounds as a function of column load was studied. The method was successfully applied to the analysis of goat cheese volatiles.
Transfer to Polymer and Long-Chain Branching in PLP-SEC of Acrylates
2009
Pulsed laser polymerization (PLP) combined with size exclusion chromatography (SEC) is the method of choice for determining propagation rate coefficients. The influence of the long-chain branching in PLP-SEC is investigated using multiple-detection SEC and a recently developed method to detect long-chain branching [P. Castignolles, R. Grab, M. Parkinson, M. Wilhelm, M. Gaborieau, Polymer 2009, 50, 2373.] While little or no long-chain branching is detected in poly(n-butyl acrylate), the error in relevant molecular weights of poly(2-ethylhexyl acrylate) is large (30-100%) due to long-chain branching. Possible variations of propagation rate coefficient with alkyl groups in alkyl acrylates or w…
Solution properties of polyelectrolytes
1993
Abstract Aqueous size-exclusion chromatography was used to analyse the elution behaviour of several standard ionic polymers, including poly( l -glutamic acid), sodium poly(styrene sulphonate) and poly(acrylic acid), different in nature and chain flexibility, as a function of the pH and ionic strength of the eluent. Two organic-based hydrophilic packings, Spherogel TSK PW4000 and Ultrahydrogel 250, were tested in order to select the optimal conditions of macromolecular separation, and the results obtained for each column were compared. A set of calibration graphs for the above polyions as a function of eluent pH and ionic strength were obtained and compared with those obtained for uncharged …
Radioactive labeling of defined HPMA-based polymeric structures using [18F]FETos for in vivo imaging by positron emission tomography.
2009
During the last decades polymer-based nanomedicine has turned out to be a promising tool in modern pharmaceutics. The following article describes the synthesis of well-defined random and block copolymers by RAFT polymerization with potential medical application. The polymers have been labeled with the positron-emitting nuclide fluorine-18. The polymeric structures are based on the biocompatible N-(2-hydroxypropyl)-methacrylamide (HPMA). To achieve these structures, functional reactive ester polymers with a molecular weight within the range of 25,000-110,000 g/mol were aminolyzed by 2-hydroxypropylamine and tyramine (3%) to form (18)F-labelable HPMA-polymer precursors. The labeling procedure…
Redox-Responsive Block Copolymers: Poly(vinylferrocene)-b-poly(lactide) Diblock and Miktoarm Star Polymers and Their Behavior in Solution
2013
The synthesis of diblock and miktoarm star polymers containing poly(vinylferrocene) (PVFc) and poly(l-lactide) (PLA) blocks is introduced. End functionalization of PVFc was carried out via end capping of living carbanionic PVFc chains with benzyl glycidyl ether (BGE). By hydrogenolysis of the benzyl protecting group a dihydroxyl end-functionalized PVFc was obtained. Both monohydroxyl- and dihydroxyl-functionalized PVFcs have been utilized as macroinitiators for the subsequent polymerization of l-lactide via catalytic ring-opening polymerization. A series of block copolymers and AB2 miktoarm star polymers was synthesized with varied PLA chain lengths. All polymers were characterized in detai…
Solution properties of polyelectrolytes
1991
Abstract Chromatographic data for sodium polystyrene sulphonate were obtained on both silica- and polymer-based size-exclusion supports using mobile phases of various pH and ionic strength. Deviations of the elution volume were observed towards both lower and higher values relative to the reference calibration graph obtained with uncharged standards. An empirical correlation is proposed in order to account for all the secondary effects observed. The general applicability of this correlation was further tested for chromatographic data obtained for a series of peptides and proteins on a silica-based support under very different eluent conditions. Deviations from ideal elution behaviour such a…
Size‐Exclusion Chromatography in Single and Mixed Eluents: Effects of Sorption of Solvent and Polymer Solutes on Novel TSK‐Gel Super AW Columns
2005
Abstract The novel TSK Gel Super AW column packing is based on a polymeric gel with residual hydrophobic and hydrophilic groups on the gel surface. These groups can act as active sites making the chromatographic support compatible both with polar and apolar eluents. This interesting property allows the elution of systems of very different polarities but also induces binary polymer–gel, polymer–solvent, and solvent–gel enthalpic interactions that lead to a mixture of separation mechanisms: repulsion, partition, or adsorption besides the main size‐exclusion chromatography (SEC) mechanism. For this reason, the elution behaviour of many and diverse polymer/solvent systems has been studied in th…
Packings of an unidimensional regular pore structure as model packings in size-exclusion and inverse size-exclusion chromatography
1996
Using porous aluminas and aluminosilicates with a regular and well-defined pore structure an attempt was made to correlate the SEC data of polystyrenes with established theoretical models. The pore structure of the two types of packings was extensively characterized by means of transmission and scanning electron microscopy, nitrogen sorption and mercury porosimetry. The SEC distribution coefficients measured experimentally were correlated with the distribution coefficients calculated from the theoretical models for flexible polymers. A good correlation was observed for the packing of the simplest pore morphology, but remarkable deviations appeared for the materials with a more complex pore …
The second component of human complement: Detection of two hemolytic forms in plasma by pH Variation
1988
The second component of human complement (C2) in pseudoglobulin prepared from normal plasma eluted as a single peak at high conductivity (30 mS) and pH 4.5 from the cationic exchangers S-Sepharose or Mono S in the Fast Protein Liquid Chromatography (FPLC) System. The C2 was stable at pH 4.5 and 0 degrees C if enzyme inhibitors were used and the pH was raised to 6.0 after elution from the columns. After rechromatography on Mono S in the FPLC System at the median isoelectric point of 5.5 or pH 6.0, the C2 eluted as two distinct hemolytic forms: the first peaked at 16 mS, the second at 30 mS. The two forms of C2 did not correlate with the allotypic variant of C2 in individual, normal human pla…
Transformation of Iodide in Natural and Wastewater Systems by Fixation on Humic Substances
2000
Separation of different fractions of humic substances (HS) by their molecular weight was carried out by size exclusion chromatography (SEC). The fixation of inorganic iodide by HS of these fraction...