Preliminary study of nickel,ferric, lead,and copper oxinates in reactions of reextraction through the exchange of ligands: The use of chloroform solutions of the copper oxinate in the spectrophotometric determination of cyanide

In this paper a systematic study of four metallic oxinates (ferric, nickel, lead, and copper complexes) is carried out, determining some characteristics of the organic solutions of these complexes in reactions of reextraction by the exchange of ligands. These reactions are based on the decoloration produced in organic solutions of colored complexes when they are mixed with aqueous solutions of anions. The study of some characteristics and the qualitative tests shows that only the copper oxinate is interesting for quantitative purposes because its solutions in chloroform are decolored at very low concentrations of oxalate ethylenediamine tetraacetate, sulfide, and cyanide.The application of this study to the indirect spectrophotometric determination of cyanide is carried out. The decoloration varies linearly with the cyanide concentration between 10 and 50 ppm for a phase volume ratio 1:1. Finally, the error, reproducibility of the method, nature of the exchange reaction, and interferences of foreign ions are also established.     

Spectrophotometric determination of anions by reextraction through the exchange of ligands: The determination of traces of oxalate using ferric indol-2-carboxylate in isoamyl alcohol

In this paper an indirect spectrophotometric method is proposed to determine oxalate, by a new technique called “reextraction through the exchange of ligands.” This new method is based on the decoloration produced in organic solutions of colored complexes when mixed with aqueous solutions of complexing anions.The established procedure for the preparation of solutions of ferric indole-2-carboxylate in isoamyl alcohol is given, as well as a discussion of the variables which influence the reextraction through the exchange of ligands.Finally, the technique was applied in determining traces of oxalate in an aqueous solution. The decoloration varies linearly with the oxalate concentration between 1 and 6 ppm. The error and reproducibility of the method were calculated. Also studied were the value of the constant of exchange and the interferences caused by various ions.     

Synthesis and studies of the antifungal activity of 2-anilino-/2,3-dianilino-/2-phenoxy- and 2,3-diphenoxy-1,4-naphthoquinones

Research on Chemical Intermediates - Several synthetic and natural naphthoquinone derivatives have been associated with antifungal activity. Candida albicans is a fungus that is known to exist in...     

Generation of benzofuroxans by photolysis of crystalline o-nitrophenylazides. A green chemistry reaction

Several benzofuroxans were obtained by photolysis of crystalline o-nitrophenylazides at ambient temperature. In this particular case, the solid matrix favored the elimination of nitrogen and exclusive formation of heterocyclic benzofuroxan. However, this reaction gives quantitative yields only with crystalline o-nitrophenylazides with a high melting point (above 50 °C).     

Development of 90Y-DOTA-nimotuzumab Fab fragment for radioimmunotherapy

Concentration of activity of Cs-137 and its spatial distribution in soils and lichen Hypogymnia physodes were determined in the Gorce Mts. (several hundred km²) in S Poland. The authors distinguished two areas of the Gorce Mts. on the basis of markedly different Cs-137 depositions, whose respective average values are 4.4 and 9.9 kBq/m² as at 1st July 2005. The average Cs-137 activity concentration in the lichen H. physodes from the Gorce is 47 Bq/kg d.m. A significant local variability of quantities measured amounts to a few dozen percent was found.     

An oxime-carbapalladacycle complex covalently anchored to silica as an active and reusable heterogeneous catalyst for Suzuki cross-coupling in water

A preformed oxime-carbapalladacycle complex covalently anchored onto mercaptopropyl modified silica is highly active (> 99%) for the Suzuki reaction of p-chloroacetophenone and phenylboronic acid in water; no leaching occurs and the same catalyst sample was reused eight times without decreased activity.     

Design, construction and testing of a system for detection of toxic gases based on piezoelectric crystals

A system for static operation of toxic gas sensors based on piezoelectric crystals was constructed as a preliminary step in the development of this type of sensor. The sensing part of the setup consists of a twin oscillating circuit assembled from commercially available electronic parts mounted on a motherboard. The oscillating circuits can accommodate two piezoelectric crystals, of which one or both can be coated with different materials, or a single one, as required. The sensing assembly (crystals plus oscillating circuits) is placed in a customized test chamber that allows one to control and reproduce its internal environment. Once assembled and fine-tuned, the proposed setup was used to test a commercially available piezoelectric crystal for sensing formaldehyde in order to expand available information on this type of sensor.     

Dielectric behavior of polyaniline synthesized by different techniques

Polyaniline doped with dodecylbenzenesulfonic acid (Pani.DBSA) was synthesized by different procedures: by a dedoping-redoping process, by one step inverted emulsion polymerization and by one step aqueous dispersion polymerization. The effect of these different techniques on the electric properties (dielectric constant, dielectric losses, and complex electric modulus) of the corresponding emeraldine base has been studied by thermal dielectric analyzer (DETA) in the temperature range −130 °C to 200 °C and in frequency range 0.03-10⁵ Hz. It was found that the preparation technique has significant influence on the dielectric properties of Pani. The different synthetic routes give rise to polyaniline with different distribution of electric relaxation process, indicating different chain structure. Emeraldine base from Pani.DBSA prepared by one step aqueous dispersion polymerization exhibits one single relaxation peak with narrow distribution whereas that prepared by inverted emulsion polymerization exhibits two relaxation peaks, indicating two-phase structure as indicated by a bimodal distribution of relaxation process. Emeraldine base from Pani.DBSA prepared by dedoping-redoping process presents an intermediary behavior. Percentage crystallinity of Pani.DBSA samples has also been investigated using wide-angle X-ray diffraction analysis. Pani.DBSA prepared by aqueous dispersion exhibited higher crystallinity degree, which agrees with the higher conductivity.