Separation of enantiomers of <Emphasis Type="Italic">N</Emphasis>-derivatives of amino acids by capillary electrophoresis using macrocyclic antibiotics

The potential for the application of macrocyclic antibiotic eremomycin as a chiral selector for the separation of enantiomers of N-derivatives of amino acids in capillary electrophoresis was estimated. The influence of several factors (the composition and pH of the running electrolyte, the concentration of the chiral selector, capillary geometry, the value of the applied voltage) on the migration of the derivatives of amino acids and enantioselectivity in the presence of eremomycin was studied in order to choose the separation conditions. Using the example of the dansyl derivatives of amino acids the enantioselectivities of vancomycin and eremomycin in capillary electrophoresis were compared.     

HPLC separation of nitrogen-containing compounds on silica gel modified with gold nanoparticles stabilized by chitosan

The potentialities of using silica gel modified with gold nanoparticles stabilized by chitosan are evaluated in the normal phase of HPLC as an example of the separation of aniline and pyridine derivatives, as well as triazole fungicides by elution with mixtures of hexane with isopropyl alcohol, isobutanol, or chloroform. The influence of the nature and content of the polar additive on the efficiency and separation selectivity of the column have been studied. The possibility of separating mixtures containing penconazole, propiconazole, diniconazole, difenoconazole, and aminopyridines is shown.     

Electrophoretic separation of nitrogen-containing drugs using silica capillaries modified with citrate-stabilized gold nanoparticles, 6,10-ionene, N-(3-sulfo,3-carboxy)-propionylchitosan and dextran sulfate

Gold nanoparticles have been widely applied in different fields of science over the last decade, e.g., in physicochemical separation methods. Two fused silica capillaries for capillary electrophoresis (CE) modified layer-by-layer with citrate-stabilized gold nanoparticles, 6,10-ionene, N-(3-sulfo,3-carboxy)-propionylchitosan (SCPC), and dextran sulfate (DS) were obtained and investigated. It has been found that the separation of the mixture of tetrahydrozoline, pindolol, terbutaline, nadolol, and hydroxyzine is fastest and most effective when the capillaries are modified with gold nanoparticles than with polysaccharide and polymers only. The most successful system for CE was obtained using DS as the polysaccharide. The enantiomers of tetrahydrozoline were separated using the capillaries modified with gold nanoparticles, 6,10-ionene, and dextran sulfate.     

Azithromycin for Enantioseparation of Tetrahydrozoline in NACE

Successful use of macrolide antibiotic azithromycin for enantioseparation of tetrahydrozoline is described in this paper. The effect of experimental parameters such as background electrolyte composition, solvent type, chiral selector concentration, temperature, and applied voltage on the enantioseparation of tetrahydrozoline was studied. The procedure was proposed for the analysis of tetrahydrozoline in pharmaceuticals. Linearity was achieved in the concentration range 5 × 10^?2–1 mg mL^?1. The azithromycin stability in the background electrolyte and the antibiotic adsorption on the fused-silica capillary were studied. Best enantioseparation with resolution factor 1.6 was achieved in less than 10 min.     

Equilibrium Plasma Configurations in the Vicinity of the Generic Point

The structure of an arbitrary equilibrium plasma configuration in an external potential field and a potential force magnetic field are studied in the plane geometry.     

Large-Scale Two-Dimensional Quantum Fluctuations of Five-Dimensional and Four-Dimensional Space-Time Metrics

Large-scale two-dimensional quantum fluctuations of five-dimensional space-time metric are constructed and the effect of the fluctuations on the nested four-dimensional worlds is studied. In doing so, the fluctuations affect not all four-dimensional worlds but only a part of them. The energy-momentum tensor of four-dimensional space-time has a physical form both in the absence and in the presence of fluctuations; it means that the fluctuations can be realized by real matter. A spatial region occupied by the fluctuations constructed in this work can be infinitely large and the fluctuations can occur during a long period of time. Therefore, we refer to these fluctuations as large-scale fluctuations.     

Matrix effect on the enantiorecognition ability of adsorbents based on heptakis(6-amino-6-deoxy)-β-cyclodextrin

Four adsorbents were synthesized by immobilizing a chiral selector, heptakis(6-amino-6-deoxy)-β-cyclodextrin, on different silica matrices, such as LiChrosorb Si 100, 10 μm; Silasorb SPH Amin, 5 μm; Kromasil 100-5-Sil, 5 μm; and Kromasil 300-5-Sil, 5 μm. The surface of adsorbents was examined by low-temperature nitrogen adsorption, and the structural properties of substrates and adsorbents were studied by electron microscopy. A matrix effect on the enantiorecognition ability of adsorbents was studied in the reversed-phase and polar-organic modes of high performance liquid chromatography using some amino acid derivatives (N-carbobenzyloxy-and tert-butoxycarbonyl-) and profens as examples. The adsorbent based on Kromasil 100-5-Sil possesses the best chromatographic properties. It was shown that the enantiomeric composition and the concentration of the active component in Ibuprofen can be determined.