Electrochemical masking of large amounts of copper in dpasv and the determination of thallium in the presence of a large excess of copper

The influence of the following surfactants on the peak of copper in 0.2M EDTA at pH 4.5 was investigated: polyoxyethylated alkylphenols having an average of 3 and 9.5 ethylene oxide units; polyoxyethylene alcohols having 4 and 7 ethylene oxide units; poly(ethylene glycols) having M.W. 4000, 9000 and 20000; hexadecyltributylphosphonium bromide (HDTBPB), tetraphenylphosphonium bromide (TPPB),N,N,N,N,N',N',N-examethylhexamethylenediammonium bromide (HMB), benzyl(di-isobutylphenoxyethoxy) dimethylammonium chloride (Hyamine 1622), hexadecyltrimethylammonium bromide (HDTMAB), hexadecyldimethylbenzylammonium chloride (HDDMBAC) and tetrabutylammonium chloride (TBAC). HDDMBAC, as well as all the substances examined which contained an ethylene oxide chain, completely suppressed the copper peak. HDTBPB and TPPB partially suppressed the peak, whereas HDTMAB, HMB and Hyamine 1622 enhanced it. TBAC was without effect. In 0.2M EDTA at pH 4.5 containing TBAC at 0.01M concentration and 10 ppm of Rokafenol N-3, Cu(II), Pb(II) and Bi(III) can be tolerated at concentrations of up to 0.05M, the height of the thallium peak being unaffected. The precision of the determination (3–10%) and the recovery are satisfactory. A 10³-fold ratio of Fe(III) to Tl(I) does not interfere with the determination.     

New Acyclic Dimers of Cholic Acid with Oxamide and Hydrazide Spacers

Summary. Three new acyclic dimers of cholic acid with oxamide and isomeric hydrazide (N,N′-diacylhydrazine) spacers were obtained. The oxamide spacers bind two identical steroidal subunits through position 3 (head-to-head dimer) or position 23 (tail-to-tail dimer). In the case of a third dimer the hydrazine moiety binds two molecules of cholic acid through position 24 (tail-to-tail dimer).     

Electrochemical studies of iodine in an aluminium chloride-butylpyridinium chloride ionic liquid part II. Neutral and basic solvent composition

The electrochemical behavior of iodine in an ambient temperature molten salt system, aluminum chloride-N-(1-butyl)pyridinium chloride (BuPyCl), have been studied in basic (excess BuPyCl) and neutral (1.0:1.0 AlCl₃: BuPyCI mole ratio) melt compositions. Acid-base interactions of iodine in different oxidation states with the ionic solvent are observed. High stability of triiodide ion in neutral butylpyridinium tetrachloroaluminate indicates relatively weak intermolecular interactions in this solvent. In basic solutions polyhalogen equilibria involving iodine in different oxidation states and chloride ions are established. In iodine and tetraethylammonium triiodide solutions a mixture of ICI₂^?, I₂Cl^?, I₃^? and I^? ions forms. The formation constants of I₂Cl^? and I₃^? and the equilibrium constant for I₂Cl^? disproportionation are estimated.     

Cyclic and stripping voltammetry of Se(+4) and Se(−2) at the HMDE in acidic media

Electroreduction of Se(+4) and electrooxidation of Se(?2) were studied at mercury electrodes in acidic media and an improved mechanism of the reduction process was proposed. This mechanism takes into account the fact that the reduction path is concentration-dependent. At lower concentrations of Se(+4), mercury selenide and hydrogen selenide are formed at various potentials. At higher Se(+4) concentrations the electrode quickly becomes covered by a rigid deposit of mercury selenide and then the reduction starts to proceed to elemental selenium. Another form of selenium was formed in the vicinity of the mercury surface due to a chemical reaction between H₂SeO₃ and H₂Se. Oxidation of hydrogen selenide proceeds similarly, in the sense that after coverage of the electrode surface by a deposit of mercury selenide the oxidation starts to proceed to elemental selenium. The cathodic stripping peak of mercury selenide can be obtained down to 2 × 10^?8M of Se(+4), but this peak is often split and therefore the determination of traces of Se(+4) by the cathodic stripping technique is cumbersome.     

Dimeric Cholaphanes with Oxamide Spacers

Summary. Two new dimeric cholaphanes with oxamide spacers were prepared. The spacers bind two identical steroidal subunits through positions 3,3′ and 24,24′ (head-to-head dimer) or positions 3,24′ and 3′,24 (head-to-tail dimer).     

Nanostructures on the Basis of Porous Alumina with Intercalated with Cholesteric Liquid Crystal

The introduction of liquid crystal materials into the porous material host will help us to get optically active nanocomposites. Nanocomposite based on aluminum oxide host with cholesteric liquid crystal is characterized by a shift of bandwidth wavelength minimum. In case of intercalation of cholesteric liquid crystals into the pores of aluminum oxide host the shift of transmittance minimum into the short wave region are observed. We analyzed the ways, which indicate the deformation of the pitch of the cholesteric helix and showed the role of capillary forces in the deformation of the pitch of cholesteric liquid crystal.     

A new method for determination of hyaluronidase activity in biological samples using capillary zone electrophoresis

The aim of the study was to develop a new capillary zone electrophoresis (CZE) method for determination of enzymatic activity of hyaluronidase. The method permits monitoring of the process of hyaluronic acid digestion by hyaluronidase. Studies were performed using CZE instrument equipped with capillary of 64.5 cm total length, 56 cm effective length and internal diameter 75 µm. Separation was performed in the phosphate buffer (pH 8.10) in the electric field of 20 kV, λ = 220 nm. The procedure was based on mixing a known quantity of hyaluronic acid and an aliquot of hyaluronidase solution, followed by obtaining CZE profiles after a known period of incubation (0.5 h). The activity of hyaluronidase was calculated using multiple regression analysis in which sizes of the peaks of the main degradation products were used. The newly developed method was fully validated and it is appropriate to evaluate the activity of hyaluronidase originating from different sources with high precision and accuracy. t‐Tests showed that there were no significant differences between results obtained using turbidimetric, viscosimetric and the new CZE method. The developed method is characterized by a short duration of analysis, low volume of analyzed sample, small amount of buffers used and low cost of analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Photovoltaic cells based on nickel phthalocyanine and zinc oxide formed by atomic layer deposition

The introduction of an ultrathin zinc oxide (ZnO) layer formed by the atomic layer deposition (ALD) technique was found to improve the operation parameters of nickel phthalocyanine (NiPc) based photovoltaic cells with a transparent bottom electrode, indium tin oxide (ITO). This improvement is attributed to several reasons, such as I) increase of photovoltaic yield in ITO/p-NiPc/n-ZnO/Al cells incorporating a hybrid heterojunction as compared to single-layer ITO/NiPc/Al cells, II) enhancement of the overall spectral response in the double-layer cells and III) extension of long-term operational stability.     

Oxidative extraction versus total decomposition of soil in the determination of thallium

An aqua regia extraction and a total decomposition of soil were compared in terms of thallium determination. A sequential extraction of soil, according to the BCR protocol, was also performed for additional information on thallium distribution in soil fractions. Certified reference material—soil GBW 07401 of Chinese origin, containing 1 ± 0.2 ppm of thallium was used in these experiments. Thallium was determined by flow injection-differential pulse-anodic stripping voltammetry (FI-DP-ASV). Only 35% of total thallium was extracted in the aqua regia extraction, while the total decomposition led to satisfactory recovery. The sequential extraction showed that only 5% of thallium in GBW 07401 is dissolvable in the four BCR procedure fractions, and that 95% of the element is entrapped in the residual parent matter. These results show that the aqua regia extraction does not ensure complete thallium extraction from soil. Surprisingly, the total decomposition is significantly less time consuming than the aqua regia extraction.     

Dimeric Cholaphanes with Oxamide Spacers

Two new dimeric cholaphanes with oxamide spacers were prepared. The spacers bind two identical steroidal subunits through positions 3,3′ and 24,24′ (head-to-head dimer) or positions 3,24′ and 3′,24 (head-to-tail dimer).