1,721,018 research outputs found
"Liquid chromatographic resolution of enantiomers on chiral amine derivative-bonded silica gel"
No full text"Thin layer chromatographic and "in situ" spectrophotometric determination of products in solid-solid thermal reaction"
No full text"Preparation and characterization of cobalt(III)bipyridine and phenantrholine complexes"
No full text"Liquid chromatographic resolution of enantiomers on optically active polyamine-bonded silica gel"
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"High-performance ligand-exchange chromatography of amino acids on chiral stationary phases"
No full textThree chiral stationary phases, obtained by grafting silica gel with (-)-trans-1,2-cyclohexanediamine, were studied for the resolution of -amino acids by ligand-exchange chromatography. The packings were prepared by bonding the chiral ligand to silica gel via different hydrocarbon spacers. Separation of the optical isomers was accomplished by eluents containing a constant concentration of copper(II) acetate (0.05mM). The elution sequence of amino acids was found to be dependent on the grafting reaction selected to prepare the chiral packings
"High-performance liquid displacement chromatography of enantiomers on a chiral poly-L-valyl-based stationary phase"
No full textA direct enantiomer separation according to the displacement mode of liquid chromatography has been developed on a silica-based stationary phase bearing as chiral selectors poly-L-valyl groups. Milligram amount resolution of DL-methionine β naphthylamide was accom plished on two analytical size columns using methanol-containing acetate buffer as the carrier and DL mande lie acid dissolved in the carrier as the displacer
Chiral separation of pesticides by coupled-column liquid chromatography application to the stereoselective degradation of fenvalerate in soil
No full textChiral separation of synthetic pesticides presenting more than one center of asymmetry was performed by multidimensional liquid chromatography. The method consisted of coupling two columns by means of a six‐port valve: an achiral column was used for the separation of the pesticide diastereomers, that were, then, individually switched into the chiral column and resolved as the corresponding enantiomers. In order to obtain optimum resolution conditions for pesticides existing as four (fenvalerate, propiconazole, and triadimenol) and eight (cyfluthrin) optical isomers, a number of coupled‐column systems constituted of an achiral (plain silica gel, γ‐cyanopropyl(CNP)‐, and γ‐aminopropyl(AMP)‐silanized silica gel) and a chiral [containing cellulose tris‐(3,5‐dimethylphenyl‐carbamate), (R)(−)‐N‐(3,5‐dinitrobenzoyl)‐phenylglycine(DNBPG), and (S)‐N‐1‐(α‐naphthyl) ethylaminocarbonyl‐(S)‐ter‐leucine, as the selectors] stationary phases were studied. Coupled‐column liquid chromatography (CC‐LC) proved to be a very effective strategy allowing the full resolution, with the exception of triadimenol, of all the investigated pesticides. The method was used for studying the stereoselective degradation of fenvalerate in soil under simulated laboratory conditions
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