Complex emulsion inversion pattern associated with the partitioning of nonionic surfactant mixtures in the presence of alcohol cosurfactant

Commercial ethoxylated nonionic surfactant mixtures containing alcohol cosurfactant exhibit a three-phase behavior whose formulation strongly varies with the water/oil ratio. As a consequence, a change in water/oil ratio can result in a sequence of up to three different emulsion inversion processes, through a combination of formulation and composition effects.     

Revealing structural effects: electrochemical reactions of butanols on platinum

Spectroelectrochemical studies on the reactivity of butanol isomers on Pt electrodes in perchloric acid medium led to the observation of structural effects that result from the different arrangements of atoms in the organic molecules. The use of differential electrochemical mass spectrometry (DEMS) to detect volatile products showed that all four isomers react on the electrode, though different product yields were observed for each compound. In spite of the differences in the electrochemical behaviour of the butanol isomers, a series of general processes accounts for the results obtained. The formation of strongly adsorbed residues by a dehydration process leading to the formation of a C=C bond was proposed for all isomers. Electroreduction of the adsorbates produces C(4) and C(3) alkanes, and the latter reveal the existence of a fragmentation process. The C(4) hydrocarbons can be formed by hydrogenation of these residues and by hydrogenolysis of alcohol molecules in the bulk solution which react at the electrode with adsorbed hydrogen. On the other hand, CO(2) is formed during electrooxidation of the adsorbed species. Partial-oxidation products containing a carbonyl group were detected from 0.2 M solutions of 1-butanol, isobutyl alcohol and sec-butyl alcohol. The tertiary alcohol tert-butyl alcohol only reacts in its adsorbed state.     

Copper(II) complexes with 4-amino-N-[4,6-dimethyl-2-pyrimidinyl]benzenesulfonamide. Synthesis, crystal structure, magnetic properties, EPR, and theoretical studies of a novel mixed mu-carboxylato, NCN-bridged dinuclear copper compound

New Cu(II) complexes of sulfamethazine (4-amino-N-[4,6-dimethyl-2-pyrimidinyl]benzenesulfonamide, HL) [Cu(2)(CH(3)COO)(2)(L)(2)].2dmf (1) and ([Cu(L)(2)].2H(2)O)(infinity) (2) were prepared and structurally characterized. Compound 1 crystallizes in the monoclinic system, space group P2(1)/n, with a = 8.9486(9) A, b = 15.0956(12) A, c = 16.542(3) A, beta = 105.584(15) degrees, and Z = 2. Compound 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 13.8097(8) A, b = 14.5765(4) A, c = 13.7853(15) A, beta = 96.033(9) degrees, and Z = 1. In compound 1 two copper ions are linked by two syn-syn acetates and two nonlinear NCN bridging groups pertaining to the deprotonated sulfamethazine ligands. Each copper center presents a nearly square planar geometry. Magnetic susceptibility data for 1 show a strong antiferromagnetic coupling with 2J = -216.7 cm(-)(1). The EPR spectra at the X- and Q-band frequencies present the signals corresponding to the dinuclear entity, being the zero-field splitting parameter, D = 0.265 cm(-)(1). The antiferromagnetic exchange coupling is discussed using DFT calculations on some model compounds with NCN bridging ligands and also on model structures with mixed mu-acetato and NCN bridges. The copper in the polymeric compound 2 is five coordinate. The CuN(5) chromophore has a highly distorted square pyramidal geometry with small axial N-Cu-N angles of 65.53(14) and 59.90(13) degrees. In the structure a sulfamethazinate anion binds to one copper through the sulfonamido and pyrimidine N atoms and to an adjacent copper via the amino N atom.     

Naproxen: Hydroxypropyl-β-Cyclodextrin:Polyvinylpyrrolidone Ternary Complex Formation

The aim of the present study was to investigate the effect of the presence of thewater-soluble polymer polyvinylpyrrolidone (PVP) MW = 24000 g/mol, on thecomplexation of the phototoxic anti-inflammatory drug naproxen, in its sodiumsalt form, with hydroxypropil-β-cyclodextrin (HP-β-CD). The datashown that the polymer interacts with the free naproxen and with thenaproxen:HP-β-CD inclusion complex. The presence of different proportions of PVP, in the 0–1%(w/w) rangesystematically increased the K_app of the naproxen:HP-β-CD inclusioncomplex formation. The cause of this increase is that the polymer interactswith the HP-β-CD with a binding constant of K₂ = 29000 ± 53 M^-1; and with the naproxen:HP-β-CD inclusion complex, to givea ternary complex naproxen:HP-β-CD:PVP. The binding constant of thisprocess was K₃ = 5350 ± 1 M^-1. NMR data revealed that in the ternary system, PVP is outside of the cyclodextrin, and therefore must be wholly or partially recovering the naproxen:HP-β-CD inclusion complex.     

High-performance liquid chromatography with evaporative light-scattering detection for the determination of phospholipid classes in human milk,infant formulas and phospholipid sources of long-chain polyunsaturated fatty acids

We developed and validated a new high-performance liquid chromatographic method for the separation of phospholipid classes in human milk, infant formulas and phospholipidic sources of long-chain polyunsaturated fatty acids (LC-PUFAs) used in paediatric nutrition. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and sphingomyelin were separated in less than 25 min using an Extrasil silica column (150 x 4.0 mm I.D., 3-microm particle size) by isocratic elution with a mixture of isopropanol-hexane-water. Phospholipids were determined by an evaporative light-scattering detector. Several chromatographic conditions were assayed to optimise the method, whose suitability is shown by the detection limits, linearity ranges and precision rates obtained. The main advantages of the proposed method are its speed and the direct determination of the main phospholipids present in human milk, infant formulas and the phospholipid sources of LC-PUFAs used in paediatric nutrition.     

Intercalation of Cyclic Amines into α-Titanium Phosphate

The intercalation of some amines (aniline, benzylamine, cyclohexylamine,piperidine, pyridine, pyrazine and piperazine) into -titaniumphosphate, Ti(HPO₄)_2×H₂O,has been investigated by the batch method and/or by exposing the host to thevapour of the amines. The changes in the interlayer distance of the solidduring the intercalation process was followed by X-ray powder diffraction.The new intercalates were characterised by chemical and thermal analysis.Materials with a monolaminar and/or bilaminar arrangement of amine moleculesin the phosphate interlayer region are obtained depending on the nature ofthe amine. Due to steric hindrance, saturated phases are not obtained forall amines studied. The thermal decomposition of the intercalates (nitrogenatmosphere), takes place in three stages: dehydration, removal of amines andcondensation of the hydrogenphosphate to pyrophosphate groups.     

Effect of hydration of polyamide membranes on the surface electrokinetic parameters: surface characterization by x-ray photoelectronic spectroscopy and atomic force microscopy

The surface and the solid/liquid interface of two polyamide membranes, one experimental (B0) and one commercial (NF45), have been characterized by X-ray photoelectronic spectroscopy (XPS), atomic force microscopy (AFM), and zeta potential, respectively. The surface roughness, determined by AFM data analysis, is different for the two membranes, and results show that the commercial NF45 membrane presents a much lower roughness than the experimental B0 membrane. XPS data indicate that the surface of membrane NF45 is similar to that of pure polyamide, while membrane B0 contains a considerable amount of impurities. The homogeneity in depth of both membranes was also studied by determining the composition profile at different analysis angles. Streaming potential along the membrane surface or tangential streaming potential (TSP) measurements with NaCl solutions at different concentrations were carried out with both membranes to determine the zeta potential and the electrokinetic surface charge density, and a correlation between membrane surface and interface parameters is made. Some differences in atomic concentrations of membrane surface elements and X-ray photoelectronic spectra of the samples used in TSP measurements and after a drying process at 90 degrees C for 24 h can be observed when they are compared with those for fresh membranes. Electrokinetic parameters for membrane NF45 (TSP, zeta potential, and surface electrokinetic charge density) obtained from three different series of measurements strongly decrease as a result of membrane use, but for membrane B0 they are practically independent of the number of measurements. This difference in the electrokinetic behavior of the two membranes has been related to the hydration process of the surface for each sample studied by XPS and AFM.     

Crystal structure of potassium tetramethylammonium hexacyanocobaltate(III) trihydrate: K3(Me4N)3[Co(CN)6]2·3H2O

The structure of K₃(Me₄N)₃[Co(CN)₆]₂·3H₂O has been determined from three-dimensional X-ray diffraction data. The unit cell is formed by parallel layers of cobalt octahedra [CoC₆] and potassium octahedra, [K(1)N₅O(1)], separated byc/2. In each layer both types of octahedra are located alternatively. The [MeN₄]⁺ tetrahedra are located in the cavities between the two layers of octahedra. The crystal structure of this compound is the first example of its type. TMC 2483     

Solid-phase extraction and determination of trace aroma and flavour components in cider by GC-MS

Summary Minor volatile compounds are responsible for the aromas of cider. A simple technique for the analysis of these components is described based on solid-liquid phase extraction followed by quantitation by gas chromatography-mass spectrometry (GC-MS). The method is quantitative for analysis of alcohols, esters, lactones, phenols, and medium and long chain-length fatty acid.     

Trehalose-based cyclodextrin analogs: cyclotrehalans (CTs)

A new concept for the de novo synthesis of artificial glyconanocavities is presented. The use of alternating α,α′-trehalose building blocks and (thio)urea segments allows the efficient synthesis of a new family of cyclooligosaccharides, namely cyclotrehalans (CTs), featuring a convex-shaped cavity with an apolar environment. CTs are designed to exhibit molecular inclusion abilities similar to that of cyclodextrins (CDs). Contrary to CDs, CTs expose the monosaccharide β-face to the inner cavity, while the (thio)urea tethers provides some conformational adaptability. High-yielding syntheses of a series of CTs and a preliminary evaluation of their inclusion properties are reported.