The analysis of dyes and dye intermediates by physico-chemical methods: I. Thin-layer chromatographic and spectrophotometric behavior of some azobenzene derivatives

Thin-layer Chromatographic behavior of 14 azobenzene derivatives was studied, suitable eluents were found, and the R_f values were determined. Spectrophotometric behavior of these substances in acetonitrile was studied, as well as the influence of acids and bases on the studied spectra. The validity of the Lambert—Beer law in a concentration region from 1 × 10_?5 to 7 × 10_?5 was verified.     

Zum Einfluß der Ringgröße auf die Struktur von Metallchelaten. IV. Palladium(II)- und Platin(II)-Komplexe pyridylsubstituierter Dialkylsulfide und -amine

The Influence of Ring Size on the Structure of Metal Chelates with Tridentate Ligands. IV. Palladium(II) and Platinum(II) Complexes of Pyridyl Substituted Dialkyl Sulfides and Amines [β-(Pyridyl-2)-ethyl]-[(pyridyl-2)-methyl]-amine(2,3-py₂tri) forms planar palladium(II) complexes [Pd(2,3-py₂tri)X]X (X = Cl, Br) occupying trans-positions as a tridentate ligand. An analogous behaviour is observed with bis[β-(pyridyl-2)-ethyl]-sulfide(3,3-py₂Stri) in the chelate compounds [Me^II(3,3-py₂Stri)X]X (Me^II = Pd, Pt; X = Cl, Br, J, SCN). On the other hand the rigid ligand bis[(pyridyl-2)-methyl]-sulfide(2,2-py₂Stri) is only bidentate in the complexes Me^II(2,2-py₂Stri)X₂ (Me^II = Pd, Pt; X = Cl, Br, J, SCN), one pyridine group does not interact with the central atom. The reasons are the angular relations within the thioether group of 2,2-py₂Stri which allow a tridentate coordination in a facial conformation (octahedral and trigonal-bipyramidal nickel(II) and copper(II) complexes), but not in a meridional one (planar palladium(II) and platinum(II) complexes). In Pt(2,2-py₂Stri)(SCN)(NCS) one thiocyanato ligand is linked by sulfur, the other one by nitrogen.     

The analysis of dyes and dye intermediates by physicochemical methods : II. Thin-layer chromatographic and spectrophotometric behavior of some water-insoluble azo-pigments

The polarographic reduction of some 4,4′-disubstituted azobenzenes in an acetonitrile medium was studied. The diffusion character of the observed limiting currents was confirmed and a mechansim of polarographic reduction proposed. The possibility of analytical application is briefly discussed.     

Analysis of Antioxidant Capacity and Antimicrobial Properties of Selected Polish Grape Vinegars Obtained by Spontaneous Fermentation

Nowadays, products of natural origin with health-promoting properties are increasingly more common. Research shows that fruit vinegars can be a source of compounds with antioxidant activity. Research on the total antioxidant capacity, total phenolic content, and antimicrobial properties against Staphylococcus aureus, Escherichia coli, and Candida albicans of grape vinegars were conducted. Moreover, gas chromatography was used to measure acetic acid content in the vinegars. The research material consisted of vinegars produced from five different grape varieties. For each variety, two variants were prepared: with and without the addition of sugar in the fermentation process. The highest antimicrobial activity against all micro-organisms was observed in vinegar produced from Solaris grapes with added sugar. The highest polyphenol content was observed in vinegar produced from the Prior grape variety with added sugar and the highest total antioxidant capacity is the Johanniter grape variety with added sugar. The vinegars examined in this study differed, depending on grape variety, in terms of antimicrobial properties, antioxidant capacity, total phenolic content, as well as acetic acid content. Sugar addition caused significant differences in the antioxidant capacity of vinegar samples.     

MA-XRF study of 15th–17th century icons from the collection of the National Museum in Krakow,Poland

In 2015, the National Museum in Krakow, Poland, started a grant from the National Programme for the Development of Humanities, its goal to investigate an important collection of old Orthodox painting, including more than 50 15th to 17th century icons originating from the territory of the historical Orthodox Diocese of Przemyśl within the borders of the Polish Kingdom. The aim of researching the iconography, provenance, and technology of the artworks was to describe their specific features and destination, in detail, and to characterise their artistic milieu. Many different techniques were used during research, such as X-ray fluorescence (XRF), X-ray diffraction, reflectography, radiography, ultraviolet–visible imaging, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy of prepared paint layer cross sections, and dendro-chronological analysis. This paper focuses on highlighting the advantages and disadvantages of the spatially resolved macro-XRF scanning (MA-XRF) technique. Most interesting results concluded from elemental distribution maps obtained through the use of Bruker, M6 Jetstream MA-XRF scanner include the following: characterisation of the type of gold and silver foil used in the icons; determination of main pigments, including the use of lead tin yellow unusual in iconography; and the noting of an interesting distribution of blue pigments as well as the presence of orpiment. Surprisingly, a considerable amount of zinc with azurite addition was observed in brown layers. The results obtained primarily highlight all the typical features of local Carpathian icon craft.     

Influence of the plasticization on free volume in polyvinyl chloride

Positron lifetime measurements in pure polyvinyl chloride (PVC) and in the plasticized PVC have been performed. Tricresyl phosphate was used as a plasticizer. Samples of the PVC were prepared with eight different plasticizer concentrations (from 0 to 35% of the plasticizer in the PVC). All of the measurements were performed in air at room temperature. A conventional fast–slow coincidence lifetime spectrometer was used for the measurements. Mean free volumes radii and fractional free volumes were calculated from the lifetime data. It has been found that the mean free volume radius is in the investigated region of the plasticizer concentrations, a linear function of the concentration of the tricresyl phosphate in the PVC. It seems that a polynomial fit can be used to describe the fractional free volume vs. the plasticizer concentration in the PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1839–1845, 1998     

Fractionation of bacteria by electrophoresis as pre-separation method before MALDI-MS detection

The present study attempted to apply the capillary electrophoresis technique for the fractionation and separation of S. Staphylococcus hominis and Escherichia coli bacteria isolated from urine samples and the detection of migrated fraction with spectrometric method. This involved the selection of suitable conditions for separation as well as the identification of pathogens. The result of the research was the separation of Gram-negative and Gram-positive bacteria, as well as their subsequent identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using two different approaches (culture of fractions on an agar plate and direct analysis of the collected fractions). The preliminary results provide a solid basis for further research on the use of electromigration techniques with LDI detection to identify pathogens such as bacteria and viruses in biological samples.     

The Last Fortress of Tin's Tyranny – Protodenitration of Nitroalkanes

Protodenitration, a direct reduction of nitroalkanes to corresponding alkanes, already spans two centuries and is enabled by various reagents. This mini-review provides a historical development of the fundamental transformation and highlights the governing position of the Ono-Tanner reaction employing tributyltin hydride. Due to the unchallenged dominance of the toxic tributyltin hydride and environmentally unpopular solvents sharply contrasting with modern ecological trends, the current situation was dubbed “the last fortress of tin's tyranny.”     

Asymmetric Organocatalysis Under Mechanochemical Conditions

Asymmetric organocatalysis is a robust methodology providing access to numerous valuable compounds while having green chemistry principles in mind. The realization of organocatalytic transformation under solvent-free mechanochemical conditions brings additional benefits in terms of yields, selectivities, and, last but not least overall improved sustainability. This overview describes developments in the use of mechanochemistry as a vehicle for asymmetric organocatalytic transformations. The material is organized according to main catalytic activation modes, starting with covalent activation and proceeding to non-covalent activation modes. The advantages of mechanochemical organocatalytic reactions are particularly highlighted, but in some cases also, limitations are mentioned. Possibilities for target compound synthesis are also discussed.     

ChemInform Abstract: Correlation Between the Electronic Structure,Effective Mass and Thermoelectric Properties of Rare Earth Tellurides Ba2MYTe5 (M: Ga,In).

The electronic structure, electronic charge density, and band gaps of Ba₂MYTe₅ (M: Ga, In) single crystals are simulated using the full potential linearized augmented plane wave package WIEN2k.