Search results for "Separation"
showing 10 items of 865 documents
Polymer- and template-related factors influencing the efficiency in molecularly imprinted solid-phase extractions
1999
Abstract This review identifies the factors of importance in the development of molecularly imprinted polymers for use in solid-phase extractions and summarizes the results obtained to date in the area of bioanalysis, pharmaceutical analysis and environmental analysis.
On the calculation of free energy of mixing for aqueous polymer solutions with group-contribution models
2010
Abstract Liquid–liquid phase separation processes are currently used as a route to prepare polymeric porous structures for various applications (membranes and scaffolds for tissue engineering). In membrane and foam fabrication technologies, binary and mainly ternary polymer solutions are used. Membrane morphology is strongly affected by phase equilibria of processing solution. In order to achieve a better control of membrane morphology and to explore a wide quantity of solvents, a predictive tool addressing experimentals would be strongly advisable. In this paper, group contribution models were chosen to test the applicability on a PLLA–dioxane–water ternary polymer solution, whose experime…
Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends. Thermal, mechanical and morphological behaviour
2011
Abstract A model epoxy resin/anhydride system, modified with a polyethersulfone (PES) engineering thermoplastic toughening agent, has been studied under hydrothermal ageing in order to investigate the modification of the thermal, morphological and mechanical behaviour through dynamical mechanical thermal analysis, SEM microscopy and fracture toughness test respectively. Two different concentrations of the toughening agent were used in the blends and two ageing conditions have been considered, consisting of the immersion of the samples in distilled water at constant temperature of 70 °C for 1 week and for 1 month. Dynamical mechanical thermal analysis results on hydrothermally aged materials…
Capillary column gas chromatographic identification of sugars in honey as trimethylsilyl derivatives.
1987
A method for identifying carbohydrates (mono-, di- and trisaccharides) in honey is presented. It is based on the separate preparation of both trimethylsilyl ethers and oxime trimethylsilyl ethers of the sugars followed by their gas chromatographic separation on a fused-silica capillary column coated with OV-101 using temperature programming. From the two chromatograms, the number of peaks given by each derivatized sugar, their relative retention times and peak-area ratios are used for identification. The identities of two unidentified trisaccharide peaks are considered. Quantitative applications to honey sugar analysis are discussed.
Modification of commercial UF membranes by electrospray deposition of polymers for tailoring physicochemical properties and enhancing filtration perf…
2020
Abstract The main challenge for a widespread use of nanoporous membranes in the removal of ionic contaminants lies in the adjustment of their physicochemical properties to allow adequate ion rejection and mitigate fouling based on the targeted application. Most of the commercial membranes are negatively charged and their use is thus not necessarily relevant for divalent cation rejection. The main objective for researchers is therefore to provide novel tailored membranes by developing specific synthesis or modifying available membranes. It is proposed here to tailor physicochemical properties of a commercial low molecular weight cut-off ultrafiltration membrane by electrospray deposition of …
Temperature influence on moisture transfer through synthetic films
2000
Abstract Water transfer through films was investigated as a function of the temperature, the physical state of water and the relative humidity (RH) difference. The films were two synthetic packagings: a hydrophobic one, the polyethylene, a hydrophilic one, the cellophane. Some phenomena which could occur at low temperatures were discussed, such as polymer structure change due to mechanical relaxation or network plasticisation and modification of the penetrant diffusion at its melting temperature. But it seems that the comparison of water permeabilities (WPs) with temperature, especially at subzero temperatures, requires the correction of their calculation with the difference of water chemic…
Enantiomeric separation of amino acids by capillary electrophoresis with α-cyclodextrin
1998
A simple method for separation of underivatized aromatic amino acid enantiomers is presented. The influence of α-cyclodextrin concentration, applied voltage and background buffer pH on the separation were investigated to achieve the best conditions of separation.
Factors influencing the transport of tryptophan hydrochloride through supported liquid membranes containing macrocyclic carriers
1997
Commercially available PTFE membranes were used as a support for liquid membranes in amino acid transport. Using tryptophan as a model amino acid, the influence of the type of organic liquid, kind of macrocyclic carrier and counter-ion on transport efficiency was examined. These studies show the strong influence of the kind of the counter-ion co-transported with amino acid cation, and the type of macrocyclic carrier used on the transport efficiency. The transport efficiency depends also on the pH of the source phase and on the nature of the organic liquid used as a membrane solvent. Liquid membranes supported on commercial porous-PTFE-membranes with hydrophobic solvents are stable for more …
Supported liquid membrane separation of amine and amino acid derivatives with chiral esters of phosphoric acids as carriers
2003
Studies on the possible use of phosphate and phosphonate esters bearing chiral menthol or nopol moieties as carriers for the transport of amines, amino acids, and amino acid esters through supported liquid membranes (SLM) are presented. Additionally, the enantioselectivity of the SLM transport of alkyl esters of aromatic amino acids and a non‐protein amino acid was also evaluated. It could be concluded that the extent of transport strongly depends on the hydrophobicity of the amino compound. Moreover, the carrier structure also influences the transport of those compounds through SLM: chiral phosphate and phosphonate esters appear to be poor or moderate carriers for enantioselective SLM tran…
Extraction of amino acids with emulsion liquid membranes using industrial surfactants and lecithin as stabilisers
2000
Abstract Industrial surfactants (being the mixtures of several individual compounds) were used as stabilisers of emulsion liquid membranes (ELMs). Although, some impurities present in technical formulations of these compounds were extracted to aqueous solutions of amino acids, most of the used surfactants well served to this purpose. In the case of amino acid transport, they do not act as carriers and application of additional carrier (such as D2EHP) was required in order to facilitate the transport. Interestingly, the same properties were found for lecithin, industrially important natural surfactant. Lecithin applied as a chiral discriminator, used either as an emulsion stabiliser or carri…