Search results for "solution"
showing 10 items of 5638 documents
Packings and stationary phases for biopolymer separations by HPLC
1987
Packings and stationary phases applied to high resolution separations of proteins, enzymes, and nucleic acids must satisfy a series of distinct criteria that are different from those usually required by HPLC of low molecular weight non-biologically active analytes. These requirements have been met through substantial improvements in classical gel media together with novel developments in silica supports, and have led to a family of products with tailor-made and reproducible properties. Supports consisting of cross-linked organic gels, and inorganic materials (mostly silicas) are now available with graduated particle sizes, pore sizes, porosities and surface areas as well as non-porous beads…
Global treatment of chromatographic data with MICHROM
1997
Abstract The program MICHROM for the general treatment of chromatographic data is presented. MICHROM takes part in all the stages of the analytical process. It allows determination of dead time, smoothing of chromatograms, measurement of peak parameters, fitting of skewed peaks, and deconvolution of overlapped peaks. Tools for the experimental design, optimization of the mobile phase composition to resolve a mixture of analytes, and simulation of chromatograms in several experimental conditions, are implemented. Routines for the graphical representation of chromatograms, resolution surfaces, contour maps, management of data series, optimization and regression analysis, are also included. Th…
Classification of Extra Virgin Olive Oils Produced at La Comunitat Valenciana According to Their Genetic Variety Using Sterol Profiles Established by…
2009
A method to classify extra virgin olive oils (EVOOs) according to their genetic variety using sterol profiles obtained by high-performance liquid chromatography (HPLC) with mass spectrometry (MS) detection has been developed. Sterol extracts were chromatographed on a dC18 Atlantis column (100x3 mm, 3 microm) with a gradient of acetonitrile/water (0.01% acetic acid) at a flow rate of 1.0 mL min(-1) and positive-ion mode MS detection. Using linear discriminant analysis of the HPLC-MS data (extracted ion chromatograms), EVOO samples belonging to six genetic varieties cultivated at La Comunitat Valenciana, Spain (Arbequina, Borriolenca, Canetera, Farga, Picual, and Serrana), were correctly clas…
Models and objective functions for the optimisation of selectivity in reversed-phase liquid chromatography.
2006
Interpretive methodologies are the most efficient tools for finding the optimal conditions in chromatography. These methodologies are supported by models or algorithms able to infer the system behaviour upon changes in the experimental factors. Once the models are built with data obtained from sets of carefully designed experiments, molecular modelling or other approaches, they can be applied to predict the performance of new conditions. The different elements involved in these methodologies, for both isocratic and gradient elution, are given. Special attention is devoted to the description of retention, owing to its major impact on the prediction of chromatographic resolution. Several mode…
Evaluation of several global resolution functions for liquid chromatography
1999
Abstract An interpretative approach, that makes use of the overlapped fraction of each chromatographic peak as elementary resolution criterion, was applied to the separation of mixtures of compounds. The elementary resolution measurements for all peaks in the chromatogram were reduced to a single numerical value using several functions: normalised by the mean resolution product, unnormalised product, geometrical mean of the unnormalised product, and worst elementary resolution value. The descriptive capability of these reduction functions was evaluated through the observation of global resolution diagrams and the change in the shape of the chromatograms in the selected factor space. michrom…
Resolution of inherently chiral resorcarene derivatives by enantioselective HPLC
1999
Abstract The HPLC enantiomeric resolution of five inherently chiral tetrabenzoxazine derivatives of resorcarenes has been achieved by HPLC using Whelk-Ol and in one case Chiralpak AD as stationary phases. Enantiomeric separation was only observed in a very narrow range of mobile phase compositions. On-column enantiomeric interconversion of a racemic compound with a typical plateau-like elution profile was observed using a Chiralpak AD column
Reversed-phase high-performance liquid chromatography of proteins and polypeptides on polystyrene-coated silica supports
1990
Abstract A new type of hydrolytically stable reversed-phase packing material prepared by multi-point covalent binding of polystyrene chains onto the surface of porous silica was examined in the high-performance liquid chromatography of proteins and polypeptides. Whereas wide-pore material was shown to give a rapid and efficient resolution of proteins, packings with smaller pores provided better selectivities for peptides.
Separation of U(VI) and Th(IV) from Some Rare Earths by Thin Layer Chromatography with Di‐(2‐Ethylhexyl)‐Dithiophosphoric Acid on Silica Gel
2005
Abstract Separation of U(VI) and Th(IV) from some rare earths by TLC has been studied using silica gel H and silica gel H impregnated with ammonium nitrate as the stationary phase. The solvent mixture ethyl‐methyl‐ketone–tetrahydrofuran (6∶3, v/v) containing di-(2‐ethylhexyl)-dithiophosphoric acid was used as the mobile phase. When silica gel H impregnated with 2.5 M NH4NO3 was used as stationary phase, the resolution was much improved and the separation of rare earths from each other was also achieved. The tetrad‐effect was observed in variation of R*m versus the atomic number of rare earths.
Methods for the rapid detection, isolation and sequence determination of “peptaibols” and other aib-containing peptides of fungal origin. I. Gliodeli…
1984
A rapid and simple detection procedure of Aib-containing “peptaibol” polypeptide antibiotics (mycotoxins) in fungal culture broths is described which employs alkylsilica (Sep-Pak®) cartridges for a selective enrichment, and the utilization of the unusualα-aminoisobutyric acid (Aib) and amino alcohols as specific marker constituents, which are easily detectable in total hydrolysates. Preparative isolations from fermentation broths is facilitated by adsorber resin (XAD) column chromatography, and purification of crude isolates is achieved by silica gel- and sephadex LH-20 chromatography. Preparative HPLC using spherical, totally porous ODS-bonded phases enables the isolation of uniform peptid…
Fast enantiomeric separation of propranolol by affinity capillary electrophoresis using human serum albumin as chiral selector: application to qualit…
2004
Abstract In the last years, capillary electrophoresis (CE) has gained considerable interest in pharmaceutical laboratories for controlling the chiral purity of drugs. This paper describes a simple and fast method for resolution of propranolol enantiomers by affinity capillary electrophoresis (ACE) using human serum albumin (HSA) as chiral selector. The effect of several experimental variables such as HSA concentration, temperature, chiral selector plug length and addition of organic modifiers, on the separation is evaluated. Complete enantioresolution of R- and S-propranolol was achieved in less than 5 min when the capillary was completely filled with 100 μM HSA solution and the electrophor…