Establishing the chromatographic fingerprints of flavan‐3‐ols and proanthocyanidins from rose hip (Rosa sp.) species

The profile of flavan‐3‐ols and proanthocyanidins in five different Rosa species (R. canina, R. glutinosa, R. rubiginosa, R. multiflora, and R. spinosissima) was estimated on high performance thin layer chromatography cellulose plates. Differences in flavanol and proanthocyanidin profiles of the extracts were evident, among which Rosa spinosissima stood out with catechin as the only detected flavanol and red zones as indication of anthocyanins. Furthermore, the elution solvent for thin layer chromatography with mass spectrometry analyses of glycosylated flavan‐3‐ols and proanthocyanidins was optimized, enabling identification of catechin, (epi)catechin hexoside, proanthocyanidin dimer, and proanthocyanidin dimers and trimers hexosides. A total of 15 flavanols and their derivatives were identified using ultra‐high‐performance liquid chromatography with linear trap quadrupole‐Orbitrap mass analyzer and epicatechin, gallocatechin, and proanthocyanidin trimer were identified only using this technique. However, proanthocyanidin trimer trihexoside was identified only by thin‐layer chromatography with mass spectrometry. To establish the relationships between the flavanols and proanthocyanidins composition of rose hip and their origin, principal component analysis was performed on the entire set of liquid chromatography/mass spectrometry data. Both principal components’ scores plots showed that Rosa spinosissima could be considered as an outlier. Our study demonstrated that flavanol and proanthocyanidin profiles of different rose hips depend on the geographical origin rather than on the cultivar and genotype.     

Multiaxial testing of materials using a stewart platform: Case study of the nooru-mohamed test

Experimental Techniques - A first application of a Stewart platform used as a multiaxial testing machine is presented. A specific case study is chosen, namely the so-called Nooru-Mohamed...     

Investigation of chromatographic conditions for the separation of ofloxacin and its degradation products

A sensitive, precise, and accurate reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for simultaneous determination of fluoroquinolone antibacterial ofloxacin and its degradation products: decarboxy ofloxacin, 9-piperazino ofloxacin, des-methyl ofloxacin, and ofloxacin-N-oxide. The proposed RP-HPLC method allowed separation of all five compounds simultaneously with the total time of the analysis not more than 15 min. The relative standard deviation (RSD) values for quantification of DOF, POF, MOF, OF, and NOF were of 0.77, 0.58, 0.51, 0.10, and 0.70%, respectively, indicating a good precision of the method. The limits of detection for DOF, POF, MOF, OF, and NOF were 0.10, 0.13, 0.06, 0.03, and 0.03 microg mL(-1), respectively. The described method can be used for simultaneous identification and quantification of all analysed compounds in different pharmaceutical formulations.     

2，6－二氯苯甲醛合成路线述评

述评了２，６－二氯苯甲醛的合成路线，着重介绍了研制该化合物的最新进展。参考文献１５篇。     

Coulometric generation of H+ ions by oxidation of thiols at a platinum anode and by oxidation of mercury in acetic acid—acetic anhydride

The coulometric generation of hydrogen ions by anodic oxidation of propane-1-thiol, butane-1-thiol, 2-mercaptopropionic acid, heptane-1-thiol, 2-mercaptoethanol, methyl and ethyl thioglycollate and p-thiocresol in acetic acid—acetic anhydride (1 + 6 v/v) is described, together with the possibility of coulometric generation of protons by mercury oxidation in the presence of p-thiocresol in the same solvent system.Current-potential curves for the solvent, indicator, titrated bases, mercury and the investigated thiols showed that in acetic acid—acetic anhydride (5 + 95, v/v), mercury and the investigated thiols are oxidized at potentials which are much more negative than those of the titrated bases and other components present in the solution.Titration of potassium hydrogenphthalate and sodium acetate with protons generated by the oxidation of thiols, and of sodium acetate, lithium acetate and pyridine with protons generated by the oxidation of mercury, demonstrated that the oxidation of both thiols and mercury proceeds quantitatively with 100% current efficiency.     

Simulation study of random sequential adsorption of mixtures on a triangular lattice

Random sequential adsorption of binary mixtures of extended objects on a two-dimensional triangular lattice is studied numerically by means of Monte Carlo simulations. The depositing objects are formed by self-avoiding random walks on the lattice. We concentrate here on the influence of the symmetry properties of the shapes on the kinetics of the deposition processes in two-component mixtures. Approach to the jamming limit in the case of mixtures is found to be exponential, of the form: θ(t) ∼ θ_jam - Δθ exp(- t/σ), and the values of the parameter σ are determined by the order of symmetry of the less symmetric object in the mixture. Depending on the local geometry of the objects making the mixture, jamming coverage of a mixture can be either greater than both single-component jamming coverages or it can be in between these values. Results of the simulations for various fractional concentrations of the objects in the mixture are also presented.     

Structural and thermal study of mesomorphic dodecylammonium carrageenates

Structural characteristics and thermal stability of a series of dodecylammonium carrageenates formed by stoichiometric complexation of dodecylammonium chloride and differently charged carrageenans (κ-, ι- and λ-carrageenan, respectively) were investigated. IR spectral analysis confirmed the electrostatic and hydrogen bond interactions between the dodecylammonium and carrageenan species. X-ray diffraction experiments show increased ordering in the complexes compared to that in the parent carrageenans. Dodecylammonium carrageenates have a layer structure, in which a polar sublayer contains layers of carrageenan chains and a nonpolar sublayer consists of conformationally disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. The major factor that determines the dodecylammonium carrageenate structure is cationic surfactant, while the carrageenans moiety plays a major role in determining thermal properties.     

Electrochemical synthesis and properties of ceria films grown on stainless steel

Electrochemical synthesis of ceria films was performed on a stainless steel substrate in view of Solid Oxide Fuel Cells (SOFC) applications. Films were obtained from aqueous nitrate solutions via cathodic deposition method at room temperature. A constant potential value of −0.8 V/(SCE) was applied to reduce the molecular oxygen as hydroxide precursor, leading to a formation of adherent, homogeneous and covering films in 20 min deposition time. Structure, morphology and composition of as-grown coatings were studied by X-ray diffraction, Raman and energy-dispersive X-ray spectroscopy, as well as scanning electron microscopy. Cubic fluorite-type nanostructured ceria of leaf-like particles was synthesized. Thermal annealing (600°C, 1 h) was found to enhance ceria crystallinity.