Micellar solutions of sulfobetaine surfactants in water-ethylene glycol mixtures: surface tension, fluorescence, spectroscopic, conductometric, and kinetic studies

Micellization in water-ethylene glycol (EG) N-dodecyl, N-tetradecyl, and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB3-12, SB3-14, and SB3-16, respectively) micellar solutions, with the weight percent of EG changing within the range 0-40, was studied by means of surface tension measurements. Information about the influence of the added EG on the aggregation number of the sulfobetaine micelles and on the polarity of the interfacial region of micelles was obtained through fluorescence and spectroscopic measurements. Surface tension measurements also provide information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, the surface pressure at the cmc, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. The Gordon parameter of the water-EG mixtures was also estimated by means of surface tension measurements. The thermodynamic and structural changes originated by the presence of EG control the micellar kinetic effects observed in the reaction methyl 4-nitrobenzenesulfonate + Br(-) occurring in the water-EG sulfobetaine micellar solutions. Information about the distribution of bromide ions between the bulk and micellar pseudophases was obtained through conductivity measurements. The kinetic micellar effects were quantitatively explained by using the pseudophase kinetic model.     

About the calculation of exchange coupling constants in polynuclear transition metal complexes

The application of theoretical methods based on the density functional theory with hybrid functionals provides good estimates of the exchange coupling constants for polynuclear transition metal complexes. The accuracy is similar to that previously obtained for dinuclear compounds. We present test calculations on simple model systems based on H. He and CH(2). He units to compare with Hartree-Fock and multiconfigurational results. Calculations for complete, nonmodeled polynuclear transition metal complexes yield coupling constants in very good agreement with available experimental data.     

Improvements on radiochemical method for the determination of Am and Cm in typical waste streams from nuclear power plants

The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates.     

Studies on the metal-nuclotide (Co-5′IMP,Co-5′GMP) interaction via mössbauer emission spectroscopy and magnetic susceptibility measurements

By means of⁵⁷Co Mössbauer emission spectroscopy and magnetic susceptibility measurements, the local symmetries and electronic structure of the Co(II) ions in the Co-5IMO and Co-5GMP complexes in the hydrated and dehydrated forms have been determined.     

Indirect spectrophotometric determination of cyanide

A spectrophotometric method for cyanide based on its inhibition of the colour formation reaction between nickel(II) and 3-(4,5-dimethyl-2-thiazolylazo)-2,6-dihydroxybenzoic acid has been developed, and allows the determination of down to 0.1 g of cyanide. Most of the interferences can be avoided by displacement of the hydrogen cyanide using an arsine generator.     

Extraction and determination of phenolic derivatives in water samples by using polyoxyethylene surfactants and liquid chromatography with photodiode array detection

Methodology based on the cloud-point phenomenon was applied to the comparative study of 3 different polyoxyethylene nonionic surfactants in order to extract and preconcentrate a group of phenolic derivatives in water samples; these phenolic compounds, which were determined by liquid chromatography with UV detection, included 11 pollutants given priority by the U.S. Environmental Protection Agency. The optimum conditions for the extraction and preconcentration of phenolic compounds were established for each surfactant. The surfactant that gave the best extraction and preconcentration of the analytes under study was polyoxyethylene 6 lauryl ether (C12E6) with detection limits of <3.5 microg/L for all the phenolic compounds tested. The method was applied to seawater and depurated wastewater samples.     

Novel terpenoids from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer). Elisapterosins A and B: rearranged diterpenes possessing an unprecedented cagelike framework

Four diterpenes and a nor-diterpenoid, all of which possess unusual carbocyclic skeletons, were isolated from the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae. The structures and relative configurations of novel metabolites elisabethin D (2), elisabethin D acetate (3), 3-epi-elisabanolide (5), elisapterosin A (6), and elisapterosin B (7) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS), chemical reactions, and X-ray diffraction analyses. The tetracyclic carbon skeleton of the elisapterosins is undescribed and constitutes a new class of C(20) rearranged diterpenes. Elisapterosin B displays strong in vitro anti-tuberculosis activity.     

Bifunctional pincer-type organometallics as substrates for organic transformations and as novel building blocks for polymetallic materials

The reactivity of the bifunctionalized ligand NC(Br)N-I 1 [IC(6)H(2)(CH(2)NMe(2))(2)-3,5-Br-4] has been studied as a versatile synthon for organic and/or organometallic synthesis. Chemoselective metalation (M = Pd, Pt, Li) at the C(aryl)-I or C(aryl)-Br bonds was achieved by choosing the appropriate metal precursors. In this way a series of Pt(II) and Pd(II) complexes were prepared that have a second functional group available for further reactions. These Pt(II) and Pd(II) complexes were subjected to a wide range of organic and organometallic reactions, revealing the remarkable stability of their M-C sigma-bond and opening an easy route for the synthesis of mono- and (hetero)bimetallic building blocks. The scope of the chemistry of such building blocks shows that they are good candidates for use in the synthesis of dendrimers, bioorganometallic systems, or polymetallic materials. The X-ray crystal structures of the most representative complexes (2, 3a, 19, 20, and 24) are also reported.     

Comparison between high-performance liquid chromatography and gas chromatography methods for fatty acid identification and quantification in potato crisps

A reversed-phase high performance liquid chromatographic (RP-HLPC) method was compared with a gas chromatography-flame ionization detection (GC-FID) method for determining fatty acids in potato crisps. Different extraction procedures were used. Fatty acids were quantified by linear regression. Both methods presented good precision (R.S.D. < or = 5.88%) and recovery (> or = 82.31%). The precision using HPLC method was slightly better than for GC-FID method. There was good agreement between the fatty acid composition of potato crisps analysed by both methods. For most purposes the HPLC method would be better. However, when more fatty acids need to be analysed, GC is a more suitable method.