A three-phase nonequilibrium model for catalytic distillation

Nonequilibrium model for steady state simulation of catalytic distillation is presented. Mathematical model takes into account both mass and heat transfers across the gas liquid interface and through the liquid-solid (catalyst) interface. Equations describing the mentioned phenomena are based on the effective diffusivity approach. The resulting system of nonlinear algebraic equations was implemented in the FORTRAN programming language and solved by the BUNLSI (Ferraris & Tronconi, 1986) solver. The described model was verified using the experimental data obtained from a continuous distillation column equipped with catalytic packing. As an experimental model system, synthesis of propyl propionate from propan-1-ol and propionic acid was chosen. Comparison of experimental and simulation data is presented, and appropriateness of the developed model for other types of catalytic distillation processes is discussed. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Coal as a New Carbon Paste Electrode Modifier with Sorption Properties

A new type of carbon paste electrode modified with subbituminous and bituminous coal is presented. The operability of the coal carbon paste electrode with respect to the working potential window attainable was tested in various electrolytes. Cyclic voltammetry of the reference redox system [Fe(CN)₆]^3?/4? was performed to evaluate electron transfer kinetics. Open‐circuit sorption of Cd(II), Pb(II), and Cu(II) with subsequent anodic stripping voltammetry was used to pilot coal sorption ability. The coal modified carbon paste electrode was also examined as a support for mercury film deposition and anodic stripping voltammetry of metals.     

Functionalized magnetic micro- and nanoparticles: optimization and application to micro-chip tryptic digestion

The preparation of an easily replaceable protease microreactor for micro-chip application is described. Magnetic particles coated with poly(N-isopropylacrylamide), polystyrene, poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate), poly(glycidyl methacrylate), [(2-amino-ethyl)hydroxymethylen]biphosphonic acid, or alginic acid with immobilized trypsin were utilized for heterogeneous digestion. The properties were optimized, with the constraint of allowing immobilization in a microchannel by a magnetic field gradient. To obtain the highest digestion efficiency, sub-micrometer spheres were organized by an inhomogeneous external magnetic field perpendicularly to the direction of the channel. Kinetic parameters of the enzyme reactor immobilized in micro-chip capillary (micro-chip immobilized magnetic enzyme reactor (IMER)) were determined. The capability of the proteolytic reactor was demonstrated by five model (glyco)proteins ranging in molecular mass from 4.3 to 150 kDa. Digestion efficiency of proteins in various conformations was investigated using SDS-PAGE, HPCE, RP-HPLC, and MS. The compatibility of the micro-chip IMER system with total and limited proteolysis of high-molecular-weight (glyco)proteins was confirmed. It opens the route to automated, high-throughput proteomic micro-chip devices.     

Computer Study of Stimuli-Responsive Polyelectrolyte Micelles in Aqueous Media. Comparison of Monte Carlo and Self-Consistent Field Approaches

The behavior of polyelectrolyte micelles with kinetically frozen hydrophobic cores in aqueous solutions was studied by Monte Carlo (MC) simulations and self-consistent field (SCF) calculations. Some results have already been published. The structure of water-soluble shells formed by weak polyelectrolytes, both pure and containing a low fraction of strongly hydrophobic units arranged either in a short sequence or distributed uniformly in the shell-forming chains was studied in detail. In the case of sequenced system, the analysis of concentration profiles of individual species reveals strong segregation and important self-organization of hydrophobic units in the shell. A comparison and critical analysis of results of MC and SCF methods is presented.     

Determination of Selected Chlorinated Priority Substances in Fish using QuEChERS Method with Dual dSPE Clean-up and Gas Chromatography

A rapid and simple analytical method for the determination of ten chlorinated priority substances (hexachloro-1,3-butadiene, pentachlorobenzene, hexachlorobenzene, hexachlorocyclohexane isomers, heptachlor, and heptachlor epoxides) in fish samples using QuEChERS extraction, dual dispersive solid-phase extraction (dSPE) clean-up, and GC analysis was developed. For the extraction, two published extraction/partitioning procedures were evaluated, and the recoveries obtained for the analytes (in range 54–98 % with RSDs ≤15 %) were in favour of the conventional QuEChERS method. The use of the dual dSPE clean-up yields cleaner extracts than in the case of single dSPE, which enables the use of ECD for the detection of the analytes and simplifies the maintenance of the GC system. The method was optimised using homogenates of chub fish that is frequently sampled for monitoring purposes. The linearity of the method was evaluated using matrix-matched calibration curves (in the range 2–50 μg kg⁻¹), and correlation coefficients (r ²) in the range 0.9927–0.9992 and RSDs of the relative response factors (RRF) below the value of 20 % were achieved. LODs ranged from 0.5 to 1.1 μg kg⁻¹, while LOQs ranged from 1.5 to 3.5 μg kg⁻¹. The accuracy of the method was verified by the analysis of the NIST standard reference material SRM 1946 (Lake Superior Fish Tissue), and most of the analytes of interest presented good agreement with the certified values.

     

Chemical shifts in nucleic acids studied by density functional theory calculations and comparison with experiment

NMR chemical shifts are highly sensitive probes of local molecular conformation and environment and form an important source of structural information. In this study, the relationship between the NMR chemical shifts of nucleic acids and the glycosidic torsion angle, χ, has been investigated for the two commonly occurring sugar conformations. We have calculated by means of DFT the chemical shifts of all atoms in the eight DNA and RNA mono-nucleosides as a function of these two variables. From the DFT calculations, structures and potential energy surfaces were determined by using constrained geometry optimizations at the BP86/TZ2P level of theory. The NMR parameters were subsequently calculated by single-point calculations at the SAOP/TZ2P level of theory. Comparison of the (1) H and (13) C?NMR shifts calculated for the mono-nucleosides with the shifts determined by NMR spectroscopy for nucleic acids demonstrates that the theoretical shifts are valuable for the characterization of nucleic acid conformation. For example, a clear distinction can be made between χ angles in the anti and syn domains. Furthermore, a quantitative determination of the χ angle in the syn domain is possible, in particular when (13) C and (1) H chemical shift data are combined. The approximate linear dependence of the C1' shift on the χ angle in the anti domain provides a good estimate of the angle in this region. It is also possible to derive the sugar conformation from the chemical shift information. The DFT calculations reported herein were performed on mono-nucleosides, but examples are also provided to estimate intramolecularly induced shifts as a result of hydrogen bonding, polarization effects, or ring-current effects.     

Synthesis of quinolines via Friedländer reaction catalyzed by CuBTC metal-organic-framework

Friedl?nder condensation between 2-aminoaryl ketones and different carbonyl compounds, catalyzed by CuBTC was investigated by a combination of various experimental techniques and by density functional theory based modelling. CuBTC exhibiting hard Lewis acid character showed highly improved catalytic activity when compared with other molecular sieves showing high concentraion of Lewis acid sites, e.g. in BEA and (Al)SBA-15. Polysubstituted quinolines were synthesized via a Friedl?nder reaction catalyzed by CuBTC under the solvent-free conditions. High concentration of active sites in CuBTC together with the concerted effect of a pair of adjacent Cu(2+) coordinatively unsaturated active sites are behind a very high quinoline yield reached within a short reaction time. Results reported here make CuBTC a promising catalyst for other Lewis acid-promoted condensations, including those leading to biologically active compounds with a particular relevance for the pharmaceutical industry. The mechanism of a catalyzed Friedl?nder reaction investigated computationally is also reported.     

Photoinduced decarboxylation of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid

Photoinduced reactions of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid (SeQCA) were investigated in alkaline media (aqueous NaOH solutions) by electron paramagnetic resonance (EPR) spectroscopy, following the in situ formation of paramagnetic species. According to UV–Vis and nuclear magnetic resonance investigations, protonation (pH ≈ 11) and deprotonation (pH ≈ 13) of the imino hydrogen of the 4‐pyridone moiety has to be considered, reflected also in the different EPR spectra observed upon irradiation. Photoinduced generation of radicals was found only for carboxylate substituted SeQCA; other studied selenadiazoloquinolone derivatives, together with those substituted at the C(8) position (R = H, COOCH₂CH₃, COOCH₃, COCH₃ or CN), did not generate paramagnetic species during exposure. Consequently, photodecarboxylation was suggested as the decisive step, accompanied by the decomposition of the selenadiazole ring, resulting in the formation of ortho‐hydroxylate anions. EPR parameters elucidated from experimental EPR spectra obtained at pH ≈ 11 and pH ≈ 13 indicate the formation of oxygen‐centered radicals at the decarboxylated 4‐pyridone ring. EPR spin trapping experiments with nitromethane confirmed a very effective photoinduced electron transfer from all the selenadiazoloquinolones investigated. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermoanalytical investigation and biological properties of zinc(II) 4-chloro- and 5-chlorosalicylates with N-donor ligands

New zinc(II) 4- and 5-chlorosalicylate complexes of general formula [Zn(X-sal)₂(L) _n (H₂O) _x ] (where X-sal?=?4-Clsalicylate, 5-Clsalicylate; L?=?N,N-diethylnicotinamide, isonicotinamide, theophylline; n?=?1, 2; x?=?0, 1, 2, 4) were prepared. The complexes were determined by elemental analysis and characterised by infrared spectroscopy. The thermal behaviour of the complexes was studied by simultaneous TG, DTG and DTA methods under dynamic air conditions. The thermal decomposition is a multi-step process. In the first step of the thermal decomposition, water is released in hydrated compounds. The anhydrous compounds start to decompose by the release of organic ligand, followed by chlorosalicylic acid, chlorophenol and carbon monoxide. The final solid product of the thermal decomposition is zinc oxide. The volatile products of the thermal decomposition were determined by mass spectrometry. The antimicrobial activities of the complexes were evaluated against selected pathogen and probiotic bacteria, yeasts and fungi strains. Bioactivities of the tested compounds are different against bacteria, yeasts and filamentous fungi. It was found that bacteria were more sensitive to the studied zinc(II) complex compounds than yeasts or filamentous fungi.     

Stimulatory action of cyclooxygenase inhibitors on hematopoiesis: a review

The presented review summarizes experimental data obtained with a mouse model when investigating the relationship between inhibition of prostaglandin production and hematopoiesis. While prostaglandin E₂ acts in a negative feedback control of myelopoiesis, inhibition of cyclooxygenases, responsible for its production, shifts the feedback to positive control. Based on these relationships, agents inhibiting cyclo-oxygenases, known as non-steroidal anti-inflammatory drugs (NSAIDs), can activate hematopoiesis and be protective or curative under myelosuppressive states. The effectiveness of therapeutic use of NSAIDs in these situations is expressive especially under the selective inhibition of cyclooxygenase-2 (COX-2), when undesirable side effects of cyclooxygenase-1 inhibition, like gastrointestinal damage, are absent. The effects of the clinically approved selective COX-2 inhibitor, meloxicam, were investigated and demonstrated significant hematopoiesis-stimulating and survival-enhancing actions of this drug in sublethally or lethally γ-irradiated mice. These effects were connected with the ability of meloxicam to increase serum levels of the granulocyte colony-stimulating factor. It can be inferred from these findings that selective COX-2 inhibitors might find their use in the treatment of myelosuppressions of various etiologies.