Search results for "liquid"

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…

Concentration of amino acids using supported liquid membranes with di-2-ethylhexyl phosphoric acid as a carrier

1997

Abstract Basic studies of a procedure for extraction of amino acids using a supported liquid membrane containing di-2-ethylhexyl phosphoric acid are presented. The extractions are made from an aqueous donor phase with pH 3 to a more acidic acceptor phase and the mass transfer is driven by the proton gradient between these phases. For 0.01 mM tryptophan and with 1 M HCl as acceptor phase, an extraction efficiency of 60% is obtained, constant up to at least 12 h. This permits concentration enrichment factors linearly increasing with time up to values of at least 150. For higher amino acid concentrations, the extraction efficiency is constant only over shorter time intervals.

ChemInform Abstract: Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.

2010

A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.

Convenient High Yielding Gram Scale Solution Synthesis of Methionine-Enkephalin.

1998

A simple, large-scale synthesis of a cytokine, methionine-enkephalin, Tyr-Gly-Gly-Phe-Met, has been elaborated. Classical solution peptide chemistry methods without protection of amino acid side-chain functions and 1+(2+2) segment condensation were used. A nine-step synthesis from commercial amino acid derivatives was developed with yields ranging from 86% to 99%, averaging 92%. The purity of all intermediates was found to be 99.0-100% by HPLC. The process has been used to prepare greater than 150 g quantities of the pentapeptide as a monohydrate of 100% purity. Hydantoin formation was observed during saponification of Boc-Tyr-Gly-Gly-Phe-Met-OMe and minimised.

Determination of albendazole and ivermectin residues in cattle and poultry-derived samples from India by micellar liquid chromatography

2021

We have developed a method, based on micellar liquid chromatography, to determine albendazole and ivermectin in dairy products and biological waste from bovine, as well as edible tissues from poultry. Anthelmitics were resolved in less than 10 min using a C18 column and a mobile phase of 0.15 mol/L sodium dodecyl sulfate – 6% 1-pentanol at buffered at pH 7 with a 0.01 M phosphate salt, running under isocratic mode at 1 mL/min. Detection was by absorbance at 292 nm. Method was successfully validated following official validation guidelines, in terms of: selectivity, sensitivity, calibration range (0.0125−0.5 mg/kg to 25−50 mg/kg), linearity (r2 > 9990), trueness (86.3–105.6%), precision (<12…

Improvement of biphasic polymerization by application of binary ionic liquid mixture

2013

Abstract The mixture of two ionic liquids, 1- n -butyl-3-methylimidazolium and 1-(2-phenylethyl)-3-methylimidazolium chloroaluminates, [C 4 -mim][AlCl 4 ] and [PhC 2 -mim][AlCl 4 ], were applied as a medium to immobilize the Cp 2 TiCl 2 titanocene catalyst for biphasic ionic liquid/hexane ethylene polymerization. The system makes possible to perform the reaction at lower temperatures, below the melting temperature of the aralkyl ionic liquid. A better separation of the ionic liquid phase was observed and an easier mass transfer of the polymer product from the ionic liquid to the hexane phase was obtained. The polyethylene reveals bimodal distribution of molecular weight. It is characterized…

1986

1982

Carbohydrates from Chemical Pulps: Characterization by Capillary Zone Electrophoresis

2006

Capillary zone electrophoresis (CZE) is one of the novel separation techniques, being applicable, for example, to virtually all important biomass-derived monosaccharides. However, in spite of this fact the utilization of this technique in the pulp and paper industry is currently rather limited. In this chapter practical guidance and some application examples are given to show how carbohydrate material (polysaccharides, oligosaccharides, and neutral and acidic monosaccharides) in pulps and spent liquors can be analyzed by CZE. Emphasis is placed on sample preparation and separation conditions including comparison with other separation methods, such as gas chromatography (GC) and high-perform…