Search results for "SIZE"
showing 10 items of 2718 documents
Surface initiated molecularly imprinted polymer films: a new approach in chiral capillary electrochromatography
2001
A new generation of imprinted composite particles was tested as capillary electrochromatography stationary phase. Silica particles characterised by a well defined particle size (10 µm diameter), shape and pore system (1000 A) were modified with an azoinitiator and subsequently used to graft molecularly imprinted polymers targeted to bind L-phenylalanine anilide. Fused silica capillaries were packed over a length corresponding to 8 cm, using a pneumatic amplification pump, and the stationary phase thus obtained was tested with respect to its electrochromatographic performance. The electroendosmotic flow mobility was evaluated with respect to both the different content of polymer on the silic…
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…
Modelling retention and peak shape of small polar solutes analysed by nano-HPLC using methacrylate-based monolithic columns.
2019
Abstract The development of methacrylate-based monolithic columns was studied for the separation of pharmaceutical hydrophilic compounds in nano-liquid chromatography. The selected polymerisation mixture consisted of 7.5% hexyl methacrylate, 4.5% methacrylic acid and 18.0% ethylene dimethacrylate (w/w), in a binary porogenic solvent (35:35 w/w 1-propanol/1,4-butanediol). The polymer synthesised with this mixture has a good permeability, not excessive back-pressure, and reasonable retention times for polar and non-polar solutes. Monolithic columns (12 cm total capillary length, 100 μm i.d.), prepared with this mixture, were able to produce hydrogen bonding and electrostatic interactions, giv…
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...
Biocompatible polymeric micelles with polysorbate 80 for use in brain targeting.
2008
In this paper, the synthesis and characterization of novel amphiphilic graft copolymers based on an alpha,beta-poly(N-2-hydroxyethyl)-D, L-aspartamide (PHEA) backbone and D, L-polylactic acid (PLA) hydrophobic side chains are reported. These copolymers were obtained starting from PHEA-ethylenediamine (PHEA-EDA), which was functionalized with polysorbate 80 (PS(80)) and/or PLA in order to obtain the PHEA-EDA-PS(80)-PLA and PHEA-EDA-PLA samples, respectively. The degrees of derivatization, DD(PS80) and DD(PLA), of PHEA-EDA-PS80-PLA, calculated by (1)H-NMR, resulted in being 1.2 +/- 0.03 mol% and 0.54 +/- 0.05 mol%, respectively, while that of PHEA-EDA-PLA was found to be 0.60 +/- 0.05 mol%. S…
Separation studies of amino acids, proteins and enzymes on bonded 1,2-dihydroxy-, 1,2-hydroxylamino-and amino silica packings
1979
1,2-dihydroxy-3-propoxypropyl (HPPS), 1-amino-2-hydroxy-3-propoxypropyl (AHPS) and 1-aminoethyl-3-aminopropyl (AEAPS) silica were synthesized by means of both a surface modification procedure (I) and a bulk modification procedure (II). Method (I) gave a surface concentration, α, of functional groups of 2–3 μmole/m2, whereas method (II) gave values up to 5 μmole/m2. Retention times, peak asymmetries and plate heights of thiamine and ascorbic acid eluted with aqueous buffer solutions ranging from pH 5.3 to 9.2 gave only a±5% variation over periods of 12 hours and more. The recoveries of selected enzymes and proteines examined under static and dynamic conditions were between 60% and 100% depen…