Cation-sensitive fluorescence of anionic polymers bearing naphtho-18-crown-6 units

Changes in the fluorescence intensity of anionic polymers bearing naphtho-18-crown-6 moieties on addition of cations were studied in water at 30 °C. On addition of alkali metal cations, the fluorescence intensity of the polymers decreased sharply for Tl⁺ less for Cs⁺ and little for Li⁺, K⁺ and Rb⁺. On addition of alkaline earth metal cations, Ba²⁺ caused the strongest decrease of the fluorescence intensity of the polymers. The decrease of the fluorescence intensity of the polymers was suggested to be caused by the external heavy-atom effect of the cations bound to the cavity of the crowned naphthalene moiety. The content of the crowned naphthalene units in the polymers affected the cation-dependent fluorescence change. The fluorescence change of the polymers based on the cation complexation competition was also studied.     

A new detection system with a microchannel plate for energy-selected conversion electron Mössbauer spectroscopy

A new measuring system using a microchannel plate and a retarding field analyzer has been introduced for use in energy-analyzed conversion electron Mössbauer spectroscopy. Mössbauer spectra of the thin surface layer of⁵⁷Fe-enriched 310 stainless steel foil were obtained by detecting scattered electrons with an energy of more than 7.0 keV. It was found that the geometries of the source, sample and the MCP were important; also, good shielding against γ-rays and X-rays was necessary in order to improve the S/N ratio.     

Interaction between dyes and polyelectrolytes. VI. Metachromatic behavior of methylene blue induced by potassium poly(vinyl sulfate) and its homologs

Effect of structure of potassium poly(vinyl sulfate) and its homologs on the metachromatic behavior of methylene blue was investigated spectrophotometrically. The metachromatic behavior with addition of polyanions was followed by the changes in the molar extinction coefficient of the 664 nm band of methylene blue and in the wavelength of metachromatic band. Important factors for metachromasy were the number of anionic sites per polymer molecule, the degree of polymerization, and the flexibility of polymer chain. It was found that the amount of KCl or urea required to destroy the metachromasy was a useful measure for estimating the binding strength of methylene blue to polyanions.     

The solubilities of azobenzene derivatives in water

Summary The solubilities of azobenzene derivatives in water have been determined at 5 °C intervals from 0° to 40 °C to obtain the information both about the effect of polar groups on the solubility of aromatic compounds in water and about the action of polar groups to the iceberg-formation in the vicinity of hydrophobic part of the solute in water environment. From the results the imaginary super cooled pure liquid has been taken as a standard state and the thermodynamic parameters of solution of azobenzene derivatives in water have been calculated.     

Determination of cadmium and bismuth in high-purity zinc metal by inductively coupled plasma mass spectrometry with on-line matrix separation

Traces of cadmium and bismuth in high-purity zinc metal were determined by inductively coupled plasma mass spectrometry (ICP-MS) in combination with flow injection (FI) on-line matrix separation (FI-ICP-MS). The anion-exchange separation method of the potassium iodide (KI) system was applied to the separation of the analytes from the matrix zinc. The analytes, cadmium and bismuth, were adsorbed on the anion-exchange (BIORAD AG1-X8) mini-column (1.0 mm i.d.× 100 mm bed length), while the matrix zinc can be completely removed from the anion-exchange resin. The analytes were eluted by 2 mol/l HNO₃ and directly introduced into the ICP-MS. The detection limits (D.L.) obtained by using a single injection (350 l) were 0.81 and 0.075 ngg^-1 for cadmium and bismuth, respectively. In the case of multi-injection concentration onto the anion-exchange mini-column (five injections 350 l each), the detection limits could be improved to 0.16 and 0.014 ngg^-1 for cadmium and bismuth, respectively. The reproducibilities of the single injection and the multi-injection method were satisfactory with a relative standard deviation of less than 5% (at the 10 and 1 ngml^-1 level for the single injection and the multi-injection method, respectively). The method was successfully applied to the determination of trace impurities in four samples of high-purity zinc metal (7 nines grade) and three standard reference materials of high-purity unalloyed zinc samples (from NIST).     

Interaction of crosslinked polyethylenimine with a homologous series of methyl orange derivatives in aqueous solution

Polyethylenimine (PEI) was crosslinked with dichloroethane, glyoxal, or glutaraldehyde and polymers of various degrees of crosslinkage were made. The insoluble polymers obtained were examined for their ability to bind methyl orange and its homologs, methyl, ethyl, propyl, and butyl orange at 5, 15, 25, and 35°C, respectively, in an aqueous solution. PEI crosslinked with glutaraldehyde showed markedly increased binding affinity toward these cosolutes compared with the polymers crosslinked with dichloroethane or glyoxal. The extent of the binding increased with an increase in the degree of crosslinkage. These results suggest that the enhancement of the binding by the crosslinking is due mainly to a dual effect, introduction of hydrophobic moieties and proximity of neighboring polymer chains. The first binding constants and the thermodynamic parameters that accompanied the binding were calculated. The thermodynamic data show that the binding process is athermal and is stabilized entirely by the entropy term. Water-soluble PEI exhibited stronger cooperative interactions than the crosslinked polymer because the mobilities of the chains of the former are greater than those of the latter.     

Remarkable stereocontrol observed in the ring formation by intramolecular hosomi-sakurai reaction

The cyclization of 2-(3′,4′-dimethyl6?′-trimethylsilyl-4′-hexenyl)-2-cyclohexenone with TiCl₄, afforded stereospecifically 6α,7α-dimethyl-6β-vinyl-5βH-1-decalone derivative and the two-fold diastereoselection involved is reasoned in terms of orientation control and folding strain control.