Search results for "SEP"
showing 10 items of 2642 documents
Analysis of amino acids using serially coupled columns.
2017
Single conventional columns in reversed-phase LC are insufficient for analysing the isoindoles of primary amino acids, due to their limited functionality. An interesting possibility for increasing the separation power is the combination of several columns of different nature, where the length is modified by coupling small segments. This approach may require a considerable investment to have multiple lengths for each stationary phase. However, the combination of only two columns of fixed length can be enough to resolve satisfactorily relatively complex mixtures, provided that an optimised gradient program is applied. In this work, a mixture of 19 primary amino acid isoindoles found in protei…
Determination of optical purity of phosphonic acid analogues of aromatic amino acids by capillary electrophoresis with alpha-cyclodextrin.
2000
A simple and efficient method for the determination of enantiomeric purity of structurally diverse phosphonic and phosphinic acid analogues of phenylalanine and phenylglycine using capillary electrophoresis is presented. These preliminary studies indicated that the enantiomer separation is strongly dependent on the structure of the aminophosphonic acid.
Chemical degradation products of lignin and humic substances part I Synthesis, structure verification and gas chromatographic separation of chlorinat…
1993
Abstract Chlorinated vanillins (4-hydroxy-3-methoxybenzaldehydes) and syringaldehydes (3,5-dimethoxy-4-hydroxy-benzaldehydes) were synthesized and their purities and structures were examined by quartz capillary gas chromatography and mass spectrometry. The detailed procedures for the synthesis, gas chromatographic separation and mass spectroscopic features are presented.
Selective CO 2 Sorption Using Compartmentalized Coordination Polymers with Discrete Voids**
2021
Carbon capture and storage with porous materials is one of the most promising technologies to minimize CO2 release into the atmosphere. Here, we report a family of compartmentalized coordination polymers (CCPs) capable of capturing gas molecules in a selective manner based on two novel tetrazole-based ligands. Crystal structures have been modelled theoretically under the Density Functional Theory (DFT) revealing the presence of discrete voids of 380 A3 . Single gas adsorption isotherms of N2 , CH4 and CO2 have been measured, obtaining a loading capacity of 0.6, 1.7 and 2.2 molecules/void at 10 bar and at 298 K for the best performing material. Moreover, they present excellent selectivity an…
Rheological study of gel phenomena during epoxide network formation in the presence of sepiolite
2012
The dynamic behaviour during the crosslinking of an epoxy polymer near the gel point was monitored using rheological multiple frequency experiments. The influence of a needle-shaped inorganic nanofiller, sepiolite, either non-modified or organically surface modified during the cure process in the presence of an aliphatic and an aromatic hardener was investigated. The validity of various criteria for determining the gel point was examined for the crosslinking of these filled thermosets. The Winter–Chambon criterion at the gel point is obeyed by the unfilled and by the non-modified sepiolite-filled epoxy matrix with either of the two hardeners. However, physical gels are formed in the presenc…
Hierarchical Imprinting Using Crude Solid Phase Peptide Synthesis Products as Templates
2003
The crude products resulting from solid-phase peptide synthesis can be used as epitope templates to generate surface-confined sites for the template and larger peptides containing the template motif. This offers a facile route to robust affinity stationary phases for the chromatographic separation of peptides.
Sesquiterpene lactones fromArtemisia barrelieri
1991
Abstract Extraction of aerial parts of Artemisia barrelieri and chromatographic separation yielded a new germacranolide, two new monocyclic sesquiterpenes and a novel germacranolide dimer, together with several known compounds.
Calculation of the molecular masses of two newly synthesized thermostable enzymes isolated from thermophilic microorganisms
1995
Two thermostable enzymes synthesized by thermophilic microorganisms were isolated and purified. A thermostable beta-galactosidase was produced in a continuous fermentation process by Bacillus stearothermophilus TP 32 as an intracellular enzyme. After applying different concentration procedures the raw extract enzyme was prepurified on a Sephadex G-200 size exclusion column. The isolated beta-galactosidase fraction was then separated with HPLC on a TSK G 3000 SW size exclusion column to determine the molecular mass based on calibration curves of standard proteins. The other enzyme, a thermostable protease, was synthesized by Bacillus stearothermophilus TP 26 as an extracellular enzyme. After…
Utilization of enzymatic detergents to clean inorganic membranes fouled by whey proteins
2005
In this work inorganic membranes used for whey protein fractionation were cleaned with enzymatic detergents. The inorganic membrane Carbosep ® M1 (Orelis S.A., France), of 150 kg/mol molecular weight cut-off and ZrO2 filtering layer, was used and the commercial detergent P3-Ultrasil ® 62 (Henkel IbS.A., Spain) was selected for the cleaning. Hydraulic and chemical methods were considered to characterize the membrane cleanliness. Cleaning efficiency was observed to be a function of the operating conditions: recycling versus non-recycling of permeate, cleaning solution pH, enzymatic agent concentration and cleaning time. The optimum conditions to perform the cleaning were related to the optimu…
Activities of Two Peptidases in Resting and Germinating Seeds of Scots Pine, Pinus sylvestris
1975
Extracts prepared from resting seeds of Scots pine, Pinus sylvestris L., rapidly hydrolysed two peptides, Leu–Tyr and Ala–Gly, at pH 8.6 and 7.8, respectively. In gel chromatography on Sephadex G-100 the two activities were eluted as separate peaks, which indicates that they are due to two different peptidases. The seeds were allowed to germinate at 20°C, the activities of the two enzymes were assayed separately on extracts from the endosperm and seedling tissues at different stages of germination, and compared with corresponding changes in dry weight and total nitrogen. Both enzyme activities were relatively high in the endosperm of resting seeds, and they increased about 2- and 3-fold dur…