Contemporary chiral simulators for capillary zone electrophoresis

For separation of enantiomers in presence of a chiral selector, data obtained with the 1D dynamic simulators SIMUL5complex and GENTRANS are compared to data predicted by PeakMaster 6, a recently released generalized model of the linear theory of electromigration. Four electrophoretic systems with stereoisomers of weak bases were investigated. They deal with the estimation of input data for complexation together with the elucidation of the origin of observed system peaks, the interference of analyte and system peak migration, the change of enantiomer migration order as function of the selector concentration and the inversion of analyte migration direction in presence of a multiply negatively charged selector. For all systems, data predicted with PeakMaster 6 are in agreement with those of the dynamic simulators and simulation data compare well with experimental data that were monitored with setups featuring conductivity and/or UV absorbance detection along the capillary. SIMUL5complex and GENTRANS provide the full dynamics of any buffer and sample arrangement and require very long execution time intervals. PeakMaster 6 is restricted to conventional CZE, is based on an approximate solution of the transport equations, provides data for realistic experimental conditions within seconds and represents a practical tool for an experimentalist.     

Crystalline Methyl β-L-Pfamnofuranqside From Fischer Glycqsidatiok of L-Rhamnose

Flash chromatography of the mixture obtained by reaction of L-rhamnose with methanol in the presence of cation-exchange resin, in addition to methyl α-L-rhamnofuranoside (3) and methyl rhamnopyranosides 1 and 2 gave methyl β-L-rhamnofuranoside (4) in 8% yield. ¹³C and ¹H NMR spectra of 3 and 4 as well as their calculated conformation in solution are discussed.     

On Evolution Galerkin Methods for the Maxwell and the Linearized Euler Equations

The subject of the paper is the derivation and analysis of evolution Galerkin schemes for the two dimensional Maxwell and linearized Euler equations. The aim is to construct a method which takes into account better the infinitely many directions of propagation of waves. To do this the initial function is evolved using the characteristic cone and then projected onto a finite element space. We derive the divergence-free property and estimate the dispersion relation as well. We present some numerical experiments for both the Maxwell and the linearized Euler equations.     

Succinobucol's new coat--conjugation with steroids to alter its drug effect and bioavailability

Synthesis, detailed structural characterization (X-ray, NMR, MS, IR, elemental analysis), and studies of toxicity, antioxidant activity and bioavailability of unique potent anti-atherosclerotic succinobucol-steroid conjugates are reported. The conjugates consist of, on one side, the therapeutically important drug succinobucol ([4-{2,6-di-tert-butyl-4-[(1-{[3-tert-butyl-4-hydroxy-5-(propan-2-yl)phenyl]sulfanyl}ethyl)sulfanyl]phenoxy}-4-oxo-butanoic acid]) possessing an antioxidant and anti-inflammatory activity, and on the other side, plant stanol/sterols (stigmastanol, β-sitosterol and stigmasterol) possessing an ability to lower the blood cholesterol level. A cholesterol-succinobucol prodrug was also prepared in order to enhance the absorption of succinobucol through the intestinal membrane into the organism and to target the drug into the place of lipid metabolism-The enterohepatic circulation system. Their low toxicity towards mice fibroblasts at maximal concentrations, their antioxidant activity, comparable or even higher than that of ascorbic acid as determined by direct quenching of the DPPH radical, and their potential for significantly altering total and LDL cholesterol levels, suggest that these conjugates merit further studies in the treatment of cardiovascular or other related diseases. A brief discussion of succinobucol's ability to quench the radicals, supported with a computational model of the electrostatic potential mapped on the electron density surface of the drug, is also presented.     

Use of inorganic, complex-forming ions for selectivity enhancement in capillary electrophoretic separation of organic compounds

Capillary electrophoresis (CE) is a powerful separation method based on the migration of charged species under the influence of electric field. The main merits of CE are high separation efficiency, short analysis time and small consumption of solvents and samples. However, the main drawbacks of CE are generally lower sensitivity compared to classical column-chromatographic methods.Selectivity and/or sensitivity of CE separation can be improved by forming complexes between analytes and a complex-forming reagent present as an additive in the background electrolyte (BGE). We focus this review primarily on the application of inorganic complex-forming reagents added to the BGE to separate organic ligands. We briefly mention common CE separations of inorganic analytes (mainly metal ions) using BGEs with organic ligands (e.g., hydroxycarboxylic or aminopolycarboxylic acids) as selectors.The review involves brief theoretical consideration of the significance of the effect of complex formation on separation selectivity and/or sensitivity in CE, but the major topic is critical evaluation of different inorganic complex-forming reagents used recently in the CE analysis of organic compounds, including:

(i)

borate, tungstate and molybdate in separating organic compounds possessing vicinal -OH groups;

(ii)

ligand-exchange CE and capillary electrochromatography in chiral analysis; and,

(iii)

the role of metal ions as central ions employed for selectivity enhancement of CE separation of various classes of organic compounds, including biopolymers.

     

Scalable production of magnetic fluorescent cellulose microparticles

Cellulose - Fluorescent and magnetic nano- and microparticles have already been used for wide range of (bio)applications. Multimodal imaging as well as simultaneous control and monitoring of...     

Characterization of copper SERS-active substrates prepared by electrochemical deposition

Surface Enhanced Raman Scattering (SERS) on copper substrates of various morphologies, prepared by electrochemical deposition on platinum targets, was investigated. The substrate preparation procedures differed by the coating bath compositions, applied current densities and the duration of individual steps. The surface morphology of the substrates was visualized by means of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). SERS spectra of selected organic thiols were measured and the relation between SERS spectral intensity and the surface structure of SERS-active substrates was studied. It has been shown that good Raman surface enhancement can be achieved on the copper substrates prepared by electrochemical deposition from ammoniac baths. Copper substrates fabricated from acidic baths did not show efficient Raman surface enhancement. The results of microscopic measurements demonstrated that the average surface roughness value does not play a substantial role, whereas the shape of the surface nanostructures is a key parameter.     

Monitoring of drugs and metabolites in body fluids by capillary electrophoresis with XeHg lamp-based and laser-induced fluorescence detection

Commercial capillary electrophoresis instrumentation with XeHg lamp-based and laser induced fluorescence (LIF) detection is employed for analysis of urinary 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) and its major metabolites, urinary metabolites of acetylsalicylic acid, urinary benzoylecgonine in an immunoassay format, and albendazole sulfoxide and albendazole sulfone in plasma. For the examples studied, the data suggest that the lamp-based detector can be employed for the monitoring of pharmacological and toxicological relevant solute concentrations, and thus represents an attractive alternative to LIF detection.     

Coaxial conducting polymer nanotubes: polypyrrole nanotubes coated with polyaniline or poly(<Emphasis Type="Italic">p</Emphasis>-phenylenediamine) and products of their carbonisation

Polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in a reaction mixture containing methyl orange. They were subsequently coated with polyaniline or poly(p-phenylenediamine) in situ during the oxidation of respective monomers in their presence. A part of the coaxial nanotubes was deprotonated using ammonia solution. The conductivity of polypyrrole nanotubes of 60 S cm^?1, was reduced after the coating, and again after the deprotonation, but maintained at a level above 10^?4 S cm^?1. Infrared and Raman spectra reflect the presence of the polymer overlayer deposited on the polypyrrole template. Thermogravimetric analysis was used as a tool for the analytical carbonisation of samples in an inert nitrogen atmosphere. The conversion of conducting polymers to nitrogen-containing carbon nanotubes was confirmed using Raman spectra.     

Impact of Taylor‐Aris diffusivity on analyte and system zone dispersion in CZE assessed by computer simulation and experimental validation

Application of pressure‐driven laminar flow has an impact on zone and boundary dispersion in open tubular CE. The GENTRANS dynamic simulator for electrophoresis was extended with Taylor‐Aris diffusivity which accounts for dispersion due to the parabolic flow profile associated with pressure‐driven flow. Effective diffusivity of analyte and system zones as functions of the capillary diameter and the amount of flow in comparison to molecular diffusion alone were studied for configurations with concomitant action of imposed hydrodynamic flow and electroosmosis. For selected examples under realistic experimental conditions, simulation data are compared with those monitored experimentally using modular CE setups featuring both capacitively coupled contactless conductivity and UV absorbance detection along a 50 μm id fused‐silica capillary of 90 cm total length. The data presented indicate that inclusion of flow profile based Taylor‐Aris diffusivity provides realistic simulation data for analyte and system peaks, particularly those monitored in CE with conductivity detection.