Band 65, Heft 4

Lipid retention in novel pressurized solvent extraction vessels was examined as a function of static and flushing cycles, flushing flow rate and flush volume in an effort to decrease lipid elution after extraction. Results indicate that none of these variables plays a pivotal role in lipid retention within this system. Regardless of which variable was altered, lipid elution remained virtually constant at (55 ± 7) %. Findings suggest that lipid elution has more to do with the high flow rate at which extracts are purged from the system at the end of the static cycle.

The present work illustrates the potential of the capillary zone electrophoresis (CZE) separation technique coupled with the on-capillary diode array detector (DAD) for highly reliable determination of curcuminoids (curcumin, CUR, demethoxycurcumin, DCUR, and bisdemethoxycurcumin, BCUR) in substances (commercially available plant extract) and pharmaceutical preparation (commercial pharmaceutical capsules) with minimal sample preparation; (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was chosen for an anionic separation of CUR and its structural analogues (DCUR and BCUR) as an appropriate complexing agent (i) providing complete resolution of the curcuminoids and (ii) reducing adsorption of these hydrophobic analytes onto the capillary wall. DAD detection was utilised for characterisation of the composition of the separated zones via differences in the corresponding UV-VIS spectra (scanned at interval of 200–800 nm). Reference and real spectra of the analytes demonstrated that the proposed separation method was sufficiently selective to produce well-separated (i.e. spectrally homogeneous) analyte zones with no interfering compounds present. Successful validation and application of the CZE-DAD method proposed here suggest its routine use in highly effective and reliable analysis of curcuminoids in pharmaceutical samples.

The aim of this work was to characterise the affinity of protein preparations from Moringa oleifera seeds, specifically extract (seeds homogenised with 0.15 M NaCl), fraction (extract precipitated with 390 mg mL−1 of ammonium sulphate) and cMoL (coagulant M. oleifera lectin) to bind humic acids using a haemagglutinating activity assay with rabbit erythrocytes and a radial diffusion assay in agarose gel. Specific haemagglutinating activity (SHA) decreased by 94 % for the extract and cMoL and by 50 % for the fraction in the presence of humic acid. Precipitation bands were observed in the diffusion gel. Both results suggested humic acid-cMoL binding. Carbohydrates, potassium, and calcium ions and pH affected the SHA of cMoL. As an example of application, cMoL was immobilised on a column packed with sepharose receiving 20 mg mL−1 of carbon humic acid solution, 30 mg of humic acid per gram of support was removed. This result suggested that protein preparations might be used in water treatment to remove humic acids.

Hybrid processes have received increased attention in the field of chemical and biochemical engineering because of their ability to overcome certain obstacles related to thermodynamics of the separation task to be carried out. Usually, in a hybrid process two processes are coupled; either reaction with separation or two different separation processes. In the design of such hybrid systems, the performance of each constituent element has to be taken into account, while their optimisation must account for their interdependency. In this paper, the methodology presented by Mitkowski et al. (2009a) is applied to design and analyse a hybrid process scheme for the synthesis of ethyl lactate. Generated hybrid process schemes have been validated through computer-aided simulations.

Recycling of ZnCl2 as a catalyst in the cyclocondensation of trimethylhydroquinone and isophytol to all-rac-α-tocopherol was studied. ZnCl2 was recycled at over 98 % efficiency in required purity by repeated extraction of the reaction streams with water, followed by switching of solvent to butyl acetate and then back to water. Recycled ZnCl2 had no negative effect on the yield of all-rac-α-tocopherol (maintaining over 90 %) at nearly total conversion of isophytol and only a 3 % molar excess of trimethylhydroquinone.

An enhanced chemical denitrification process was studied as an alternative treatment of nitrate-rich wastewater which cannot be easily treated using conventional biological methods. To accelerate denitrification and to reduce the conversion to ammonia, nitrite reductants were added. In a batch test with the initial nitrate concentration of 500 mg NO3− -N per L, sulfamic acid and zinc were found to be the best nitrite and metal reductants, respectively. In a column test with the initial nitrate concentration of 500 mg NO3−-N per L, optimum results were experimentally obtained over a zinc scrap column with a 1.0 molar ratio of [NH2SO3H]/[NO3−-N] and the recirculating flow rate of 6 L min−1 at pH 2.5. Approximately 98.8 % of nitrate anions were removed, and the observed reaction rate constant (k) was 0.135 min−1. Zinc consumption was reduced to 46.6 % compared to the procedure without sulfamic acid, and sulfamic acid consumption was reduced to 40 % compared to the results of our previous study. Based on these experimental results, it was concluded that chemical nitrate denitrification using sulfamic acid and zinc scrap is an effective alternative treatment protocol for nitrate-rich wastewater.

In this work, long-term operation of a pilot scale mixed anaerobic reactor processing crude glycerol and rapeseed meal is discussed. These materials are generated as by-products of biodiesel production. Mixed reactor was operated under mesophilic conditions for the period of 654 days. Total cumulative production of biogas reached 379 m3 (at atmospheric pressure and ambient temperature). Maximum volumetric loading achieved during the operation was 2.17 kg m−3 d−1 for the crude glycerol dose of 2 L. When dosing crude glycerol as a single substrate, average specific production of biogas of 0.76 m3 per L of the g-phase was achieved. The lack of nutrients in the g-phase had to be compensated by an addition of ammonium nitrogen in the form of urea into the reactor. Long term processing of crude glycerol demonstrated that accumulation of dissolved inorganic salts in the reactor can lead to inhibition of the methanogenic activity of microorganisms, causing breakdown of the system. Co-fermentation of crude glycerol with rapeseed meal provided stable biogas production and it was shown to be a feasible way of anaerobic degradation of these substrates. At the maximum volumetric load of 1.33 kg m−3 d−1 (500 mL of g-phase and 500 g of rapeseed meal), the average biogas production reached 0.58 m3 d−1.

Nucleation of Mg(OH)2 was investigated by measuring the electrical conductivity and pH of the Mg(NO3)2 reaction solution to which ammonia containing different amounts of NH4NO3 was added. NH4NO3 increases solubility and slows down precipitation of Mg(OH)2 in the system. Data are presented on the influence of NH4NO3 on the solubility of Mg(OH)2 at 25°C. The phenomena observed can be explained by the solvation effect of nitrate ions brought to the system with the addition of ammonium nitrate, which was proved by NMR spectroscopy. When the mass fraction of NH4NO3 exceeds 15 %, homogeneous nucleation does not proceed. It was found that seeding of the system with Mg(OH)2 crystals only influenced the rate of Mg(OH)2 crystallisation, not the size and shape of the crystals. Primary crystals are smaller than 0.1 μm. The large difference in the surface energy of individual crystal planes leads to oriented agglomeration. This process is accelerated in a pressure reactor at 130°C. The resulting polycrystals are hexagonal plates 0.2 μm thin with a diameter of 1–2 μm. Under variable reaction conditions, agglomerates as big as 30 μm can be prepared.

Porous anodic films containing nickel were prepared by AC electro-deposition. The porosity of the films was controlled by using different working conditions (anodisation electrolyte, voltage, and time). Then nickel was electro-deposited using an alternating voltage. The impact of the anodic film on the current density waveforms and the metal content can largely be explained by the porosity differences, while changing the deposition time caused changes due to over-oxidation of the aluminium substrate, experimentally proved by TEM. Finally, the impact of deposition time on the deposited metal was successfully fitted using an Elovich type law over a large time-span (up to 1800 s), showing the ability to achieve precise control of the metal content.

Treatment of N,N′-methylenedipyridinium dichloride [C5H5N-CH2-NC5H5]Cl2 with MCl2 (M = Zn or Cd) in aqueous solution gives the organic-inorganic hybrid ionic compounds [C5H5N-CH2-NC5H5] · [MCl4]. Both complex salts were fully characterised by multinuclear NMR spectroscopy, elemental analysis, and their molecular structures confirmed by powder X-ray diffraction studies. The most striking feature in both solid state structures was the presence of the C…Cl-M short contacts between the organic [C5H5N-CH2-NC5H5] dication and inorganic [MCl4] anion, which led to different crystal packing. For [C5H5N-CH2-NC5H5]·[ZnCl4], the C…Cl-Zn interactions led to the alternating arrangement of [C5H5N-CH2-NC5H5]2+[ZnCl4]2− to form 1-D chains in the direction [010], and each individual chain had a two-fold rotational axis along the b axis, while for [C5H5N-CH2-NC5H5] · [CdCl4] the C…Cl-Cd associations gave 2-D network. In both solid state structures, the presence of Cl-ring centroid distances gave a strong indication of some form of Cl-π interactions.

Poly(ethylene glycol)-block-poly(γ-benzyl l-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesised by the ester exchange reaction of PEG-block-PBLG copolymer with mPEG. The self-association behaviour of PEG-b-PBLG-g-PEG in mixtures of ethanol, chloroform, and trifluoroacetic acid as denaturing acid was investigated by transmission electron microscopy, nuclear magnetic resonance spectroscopy, FT-IR spectroscopy, dynamic light scattering, and viscometry. It was revealed that the increase in denaturing acid content in the mixed system not only promoted the critical micelle concentration but also changed the morphology of the polymeric micelles from elliptical to spherical.

A series of poly(γ-benzyl l-glutamate) (PBLG)/polyurethane (PU) containing carboxyl group blend membranes was prepared by casting the polymer blend solution in dimethylformamide (DMF). The surface morphology of the PBLG/PU blend membranes was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG/PU blend membranes were studied by differential scanning calorimetry (DSC), tensile tests and other physical methods. It was revealed that the introduction of PU could exert outstanding effects on the morphology and the properties of PBLG membrane.

Mie computations are performed to evaluate light scattering on the virtual microstructures relevant to lithium disilicate glass internal crystallisation. The computations are expressed in the form of optical transmission (OT) patterns evolved on a scale of growing lithium disilicate crystals. Input data include the crystals number density, their size, the wavelength of the incident electromagnetic radiation, the indices of refraction of the lithium disilicate glassy and crystalline phases and the thickness of the virtual glass slab. In the computations, the spherical shape of crystals and their random distribution are assumed. The results reveal the quantitative effects of individual input data constants on the overall course of the computed OT patterns. They also relate the computed OT data magnitudes to the corresponding glass crystallinity (α). In addition, they point to singular combinations of the input data constants defining the conditions under which the OT data could potentially stand for the kinetically important α data. Finally, the results aid better recognition of some fundamental as well as practical properties of the optical thermal methods based on the optical transmission measurements.

The 1,2-diphenylethylenediamine-based neutral or cationic organogelator-templates, currently employed in the production of silica nanomaterials, were initially evaluated for their versatile gelation ability and found to be gelled in the majority of organic solvents tested. Scanning electron microscope and transmission electron microscope, images of neutral organogels made from different solvents revealed that they assembled into a plate-shaped, or rod-shaped morphology, respectively in ethanol or butan-1-ol and in acetonitrile or tetrahydrofurane. Similarly, a 1: 1 mixture (mass) of neutral and cationic gelators formed different morphologies in the solvents tested. Sol-gel polycondensation of tetraethoxy silane using either individual gels (neutral or cation) or a 1: 1 mixture of gels was explored. The experimental results and the scanning electron microscopy and transmission electron microscopy images revealed that silica nanotubes with an inner diameter of 82 nm and an outer diameter of 620 nm were obtained from the 1: 1 mixture of neutral and cationic gelator in ethanol, whereas silica nanoparticles were obtained using gels made in the other solvents tested.

Polycondensation reactions of phenols with phthalic anhydride were carried out in the presence of ferric hydrogensulphate under melt conditions. The reactions proceeded in short reaction times by using a catalytic amount of Fe(HSO4)3 and the corresponding fluorescein derivatives were obtained in high yields. The simplicity, scale-up, along with the use of an inexpensive, non-toxic, recyclable catalyst of an environmentally benign nature, are other remarkable features of the procedure. The absorption and emission properties of these fluorescein derivatives were studied.

p-Aminobenzene sulfonamide (sulfanilamide, SN) is the simplest and most-used sulfonamide medicine. The key step of SN production via the commonly used chlorosulfonic acid routine is the synthesis of p-acetaminobenzenesulfonyl chloride (P-ASC). A large amount of HSO3Cl has to be used in the traditional process, which results in serious environmental problems. In this study, an alternative chlorosulfonic acid process to synthesize P-ASC was investigated by partially substituting HSO3Cl by PCl5 as the chlorination agent. Compared with the traditional process, the molar ratio of HSO3Cl to acetanilide (the main raw material) can be decreased from 4.96 to 2.1 using CCl4 as the diluent; also, addition of a small amount of NH4Cl was found to significantly increase the P-ASC yield. Operating conditions of the reaction were studied first by single-factor experiments and later by orthogonal experiments to obtain optimum operating conditions under which the P-ASC yield can reach as high as 86.3 %.

An efficient, convenient, and novel one-pot method of 2,4,5-triaryl-1H-imidazoles synthesis using benzil, arene carbaldehydes, and ammonium acetate, catalyzed by uranyl nitrate hexahydrate [UO2(NO3)2·6H2O] supported on acidic alumina and resulting in good to excellent yields under heterogeneous conditions, is reported. Formation of a reactants-catalyst complex was confirmed by UV-VIS spectral data. Antibacterial (MIC) and antioxidant activity of the synthesized compounds was also studied.

5-O-(t-Butyldimethylsilyl)-3-deoxy-3-C-hydroxymethyl-1,2-O-isopropylidene-3-(methoxycarbonylamino)-α-d-xylofuranose IV has been proved to be an appropriate building block in the stereoselective synthesis of methyl (4S)-4-[(1′R)-1′-acetoxy-4′-oxobutyl]-3-benzyl-2-oxooxazolidine-4-carboxylate III representing the polar part of the naturally occurring mycestericins E and mycestericins G.

An efficient one-pot method for regio- and stereoselective synthesis of 5-(trifluoromethyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidines under solvent-free and catalyst-free conditions has been developed. The method involves employing a three-component condensation reaction of an aromatic aldehyde and ethyl 4,4,4-trifluoro-3-oxobutanoate or 1,1,1-trifluoropentane-2,4-dione in the presence of 1,2,4-triazol-3-amine at 90°C.

Building-up a detailed kinetic model for drug release from various supports is a difficult task, especially when chemical reactions take place, accompanied by adsorption-desorption and diffusion steps. Often, semi-empirical release models derived from theoretical formulations of the transport process and system characteristics are employed. Their parameters have limited validity as they are dependent on the support, drug-ligand properties, and release conditions. However, they are often used for a quick simulation and design of drug delivery systems with a controlled release correlating the model parameters with the system characteristics and release conditions. Detailed information allows elaboration of an extended mechanistic model; the bias in the predictions introduced on various levels of model simplification is presented in this paper. A case study of a chemically activated ligand release in human plasma from a multivalent dendrimeric support is approached, pointing out the imprecision introduced by the gradual simplification of an extended model as well as the low reliability of the prediction when using various semi-empirical global models.

A novel dicalix[4]pyrrolyl-substituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye I with an absorption peak at approximately 670 nm and an emission peak at about 690 nm was prepared. As an anion receptor, I displayed a red shift in absorption spectra and fluorescence quenching in varying degrees in the presence of F−, AcO−, H2PO4−, or Cl−. Compared with the parent calix[4]pyrrole, a representative anion receptor, I exhibited a stronger affinity to these anions due to the formation of a sandwich complex through multiple hydrogen-bonding interactions.

The electronic and vibrational properties of [Fe(NHis)4(SCys)] sites responsible for the catalysis of superoxide reduction in two types of superoxide reductase (SOR), one-iron superoxide reductase (1Fe-SOR) and two-iron superoxide reductase (2Fe-SOR), were compared previously (Clay et al., 2003); the differences between these two classes of SOR, examined by UV-VIS and NIR absorption, VTMCD, and vibrational spectroscopy techniques, were interpreted as being indicative of weaker Fe-S bonds in 2Fe-SOR in comparison with 1Fe-SOR. Here, we report on density functional (DFT) and semi-empirical (ZINDO/S-CI) calculations exploring the extent of this difference in bonding between the two classes of SOR. The differences observed experimentally between the electronic spectra of the two SORs are shown to probably arise either from different degrees of torsion between the Fe—ligand bonds or from differences in length of the Fe—carboxylate bond, but are shown to be incompatible with any significant differences in Fe—S bond lengths. The differences observed in the vibrational spectra between the two SORs are shown to correlate with differences in the Fe-S bond length of no more than 0.01 Å, which in turn arise from slight differences in the polarity of the medium surrounding the iron active site in the two proteins.

A series of 36 substituted 2-phenylindoles was analysed using minimal topological difference-projections in latent structures variant (MTD-PLS) and molecular docking, using fast rigid exhaustive docking (FRED) and AutoDock Vina programs. For quantitative structure activity relationships (QSAR) validation, a sphere exclusion algorithm in the multi-dimensional descriptor space was used to construct training and test sets. Docking procedures were based on X-ray crystallography studies using the human alpha oestrogen receptor-17β-oestradiol complex. The ranking abilities of the different scoring functions of the FRED package were presented, and the most suitable scoring function (Chemgauss3) for the oestrogen receptor was chosen. Although the series studied contains only a limited number of compounds, the MTD-PLS method and the docking procedure provided coherent results in concordance with the X-ray diffraction data for different ligand-oestrogen receptor complexes.