Nickel as a chemical modifier for sensitivity enhancement and fast atomization processes in electrothermal atomic absorption spectrometric determination of cadmium in biological and environmental samples.

A systematic study of the efficiency of protons, Ni, Pd and Th as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry (ETAAS) using fast temperature programs was made for platform atomization. A comparison was made in terms of the salt type, absorbance-time profiles and elimination of the sodium chloride interference. The results were adapted to develop a method for the ETAAS determination of cadmium in biological and environmental samples. The highest sensitivity to determine cadmium in biological and environmental samples was obtained using nickel (together with protons) as a chemical modifier. The accuracy of the method was tested by the determination of cadmium in different certified reference materials. The best detection limit and the characteristic mass of Cd were found to be 0.03 ng mL(-1) and 0.35 pg, respectively.     

The phase diagram of the lyotropic nematic mesophase in the TTAB/NaBr/water system

The phase diagram of the nematic mesophase present in the tetradecyltrimethylammonium bromide/sodium bromide/water ternary system was determined. A calamitic nematic mesophase (N_C) was observed which extends to very high concentrations of electrolyte. The order parameters of the surfactant head group in the mesophases were studied by the NMR quadrupolar splitting of the deuterated surfactant. On increasing the temperature of nematic mesophases with low electrolyte concentrations, a phase separation occurs with the formation of a more highly ordered hexagonal phase and an isotropic phase. Diffusion measurements of the isotropic micellar solution by the NMR PFG method were used to estimate hydrodynamic radii at low surfactant concentrations and to study micelle diffusion as the concentration of the surfactant was increased to the liquid crystalline region. At higher surfactant concentrations, the diffusion coefficient reached a limiting value. The calamitic nematic mesophase in this surfactant/electrolyte/water system appears to be formed by long wormlike micelles.     

Synthesis and characterization of functional gradient copolymers of allyl methacrylate and butyl acrylate

Functional spontaneous gradient copolymers of allyl methacrylate (A) and butyl acrylate (B) were synthesized via atom transfer radical polymerization. The copolymerization reactions were carried out in toluene solutions at 100 °C with methyl 2‐bromopropionate as the initiator and copper bromide with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst system. Different aspects of the statistical reaction copolymerizations, such as the kinetic behavior, crosslinking density, and gel fraction, were studied. The gel data were compared with Flory's gelation theory, and the sol fractions of the synthesized copolymers were characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. The copolymer composition, demonstrating the gradient character of the copolymers, and the microstructure were analyzed. The experimental data agreed well with data calculated with the Mayo–Lewis terminal model and Bernoullian statistics, with monomer reactivity ratios of 2.58 ± 0.37 and 0.51 ± 0.05 for A and B, respectively, an isotacticity parameter for A of 0.24, and a coisotacticity parameter of 0.33. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5304–5315, 2006     

Determination of gallium by anodic stripping square-wave voltammetry Detection of a GaZn intermetallic compound and its destruction by Sb in an NaSCNNaClO(4) supporting electrolyte

Reproducibility for successive determinations with a hanging mercury drop electrode is assessed in relation to solution stirring, drop size and back-diffusion to the mercury thread. The effect of experimental parameters such as drop size, deposition time and gallium concentration on the observed stripping current is investigated. The interference of zinc present in a 0.5M NaSCN + 4.2M NaClO(4) supporting electrolyte on the gallium detection limit and calibration plots is described. Formation of an intermetallic compound with a Zn:Ga ratio of 2:3 and its destruction by co-deposition of zinc with Sb are reported. A detection limit of 10(-8)M gallium was obtained in the presence of 10(-5)M Sb(III).     

Magydardiendiol,diterpenoid with a new skeleton from magydaris panacifolia (umbelliferae).

Three new diterpenoids with a substituted α-cyclogeraniol skeleton have been isolated from the umbelliferae $\text{Magydaris panacifolia}$ (Vahl) Lange, for which the names of magydar-2,13-dien-11,17-diol, $\text{1}$, magydar-2,10 (20), 13-trien-17-ol, $\text{2}$, and magydar-2,10(20), 13-trien-17-yl acetate, $\text{3}$, are proposed. The structures of these substances have been deduced from spectroscopic and chemical data.