Internal standardization for the determination of cadmium,cobalt, chromium and manganese in saline produced water from petroleum industry by inductively coupled plasma optical emission spectrometry after cloud point extraction

In the present paper a procedure is proposed for the determination of traces of Cd, Co, Mn and Cr in petroleum industry produced water by inductively coupled plasma optical emission spectrometry. The procedure is based on cloud point extraction of these metals, as their dithizonate complexes, into the surfactant-rich phase of octylphenoxypolyethoxyethanol surfactant (Triton X-114). Extractions were carried out in solutions with salinities between 10‰ and 70‰. Since residual salinity in the surfactant-rich phase caused differences in its transport to the plasma, yttrium was used as an internal standard to correct for this effect. The simultaneous metal extraction procedure was optimized by response surface methodology using a Doehlert design and desirability function. Enhancement factors of 21, 21, 9 and 19, along with limits of quantification of 0.093, 0.20, 0.73 and 1.2 μg L^− 1, and precision expressed as relative standard deviation (n = 8, 20.0 μg L^− 1) of 5.8, 1.2, 1.7 and 5.7% were obtained for Cd, Co, Mn and Cr, respectively. The accuracy was evaluated by spike recovery tests on the high salinity water samples with salinity of 40 and 63‰.     

Chemical Reactivity of Tetrasulfur Tetranitride: Synthesis,Physical Properties,and Structural Characterization of the Amorphous Phase Cu7S4N4

Tetrasulfur tetranitride, S₄N₄, reacts with elemental Cu within inert solvents to a black‐blue material of approximate composition Cu₇S₄N₄ which is totally amorphous to X‐rays and which cannot be made crystalline by either thermal treatment or electron radiation. Cu₇S₄N₄ explodes if heated above 234 °C or when subjected to mechanical shock to eventually yield copper(I) sulfide; this together with the characteristic infrared spectrum of Cu₇S₄N₄ indicates the presence of molecular S₄N₄ units inside the amorphous phase. The metastable nature of Cu₇S₄N₄ is also mirrored by electron microscopy which furthermore allows the structural characterization of its degradation products. Based on experimental EXAFS data offering characteristic Cu—N and Cu—S distances, a theoretical crystalline approximant of Cu₇S₄N₄ was suggested and structurally optimized by density‐functional total‐energy calculations including periodic boundary conditions. This model incorporates a central S₄N₄ unit bonded to three shells of Cu atoms of different functionalities; in addition, a partial rupture of the S₄N₄ unit is likely to allow for a lowering of the total energy of the metastable phase. The latter observation supports the impossibility to make Cu₇S₄N₄ crystallize using ₄N₄ crystallize using whatever kind of measures.     

Anhydrous α-lactose A study with DSC and TXRD

The dehydrated lactose forms α_H and α_S were investigated by time- and temperature-resolved X-ray powder diffractometry and differential scanning calorimetry. We found different X-ray structures for these two forms, which is probably related to the different dehydration processes. The rapidly dehydrated form α_H obviously has the same X-ray structure as the starting material α-lactose monohydrate, although the crystallinity is reduced. A thermally induced transition of the α_H-form into the α_S-form was observed. This transition should allow one to “switch” between the physicochemical properties of the excipient, which may be important for applications in pharmaceutical and food industries.     

Droplet evaporation study applied to DNA chip manufacturing

DNA chips are potentially powerful technologies for genotyping and gene expression profiling that rely on comparative analyses of up to thousands of "spots of analysis" on a glass support. The spot quality throughout the support influences spot-to-spot variations within an array and the repeatability of data across experiments. For glass slide DNA microarrays, droplets of DNA solution are deposited on functionalized glass slides and left to react through complete evaporation of the droplet. On hydrophobic flat surfaces, different modes of droplet evaporation can be attained. Under atmospheric pressure, water droplets tend to evaporate under two main regimes. Initially, the droplet flattens with a constant contact area, and then the droplet shrinks at a constant contact angle. As a result, the diameter and morphology of thousands of spots on microarrays are not uniform. This leads to poor and unreliable data processing results. In this work, we report the evaporation of an aqueous solution under a constant contact area mode. Evaporation under reduced pressure and the effect of reagent additives to the solution have been investigated. Video microscopy and digital image analysis techniques were applied to monitor the evaporation of the droplets. A mixture of surfactants was developed to maintain a constant area regime during evaporation and to form homogeneous spots. The control of some physicochemical properties (wetting, evaporation rate) of the droplet allows the formation of well-controlled spots compatible with DNA grafting. The influence of surfactant molecules on the mechanisms of evaporation is also discussed.     

Polysulfonylamine. XLI. Ein Silber(I)-Hydrat ungewöhnlicher Zusammensetzung: Röntgenstrukturanalytische und thermochemische Charakterisierung von Tetrakis(dimesylamido)aquatetrasilber(I) [Ag4(N(SO2CH3)2}4(H2O)]

Polysulfonyl Amines. XLI. A Silver(I) Hydrate with an Unusual Composition: Characterization of Tetrakis(dimesylamido)aquatetrasilver(I) [Ag₄(N)SO₂CH₃)₂}₄(H₂O)] by X-Ray Diffraction and Thermal Analysis The title compound is obtained by crystallizing AgN(SO₂CH₃)₂ from water at room temperature. Crystallographic data (at ?95°C): Triclinic space group P1 , a = 864.6(4), b = 1 211.2(5), c = 1 399.1(5) pm, α = 90.97(3), β = 90.90(3), γ = 98.25(4)°, V = 1.4496 nm³, Z = 2, D_x = 2.608 Mg m^?3. The four independent silver atoms and the water molecule form zigzag chains Ag(1)-Ag(2)-(μ-H₂O)-Ag(3) …? Ag(4) …? Ag(1′) with distances Ag(1)-Ag(2) 309.7, Ag(2)-O(w) 241.8, O(w)-Ag(3) 241.4, Ag(3) …? Ag(4) 342.9, Ag(4) …? Ag(1′) 361.4 pm. The catenated silver atoms are further connected by the dimesylamide anions acting as tridentate bridging (α-O, N, ω-O)-ligands. The resulting strands are interconnected into layers through one O(S)-Ag′ contact (247 pm) and one hydrogen bond O(w)-H(l) …? O′(S) per repeating unit. Between the layers, a weak O(S) …? Ag″ interaction (271 ptn) and a hydrogen bond O(w)-H(2) …? O(S) per repeating unit are observed. The silver atoms Ag(l) to Ag(4) display the coordination numbers 5 [NO,Ag(2), distorted trigonal bipyramid], 5[NO₂,O(w)Ag(I), distorted trigonal bipyramid], 5[O₄,O(w), trigonal bipyramid], and 2 + 1 (N₂, li-near; plus a secondary Ag …? 0 contact). The dehydration of the title compound and a solid-solid phase transformation in anhydrous AgN(SO₂CH₃)₂, were quantitatively investigated by thermoconductometry and time- and temperature-resolved X-ray diffractometry (TXRD).     

Hydrogel networks of poly(ethylene oxide) star-molecules supported by expanded polytetrafluoroethylene membranes: characterization, biocompatibility evaluation and glucose diffusion characteristics

The present work discusses the grafting by electron beam irradiation of poly(ethylene oxide) (PEO) star-shaped polymers onto porous expanded polytetrafluoroethylene (EXPTFE) surfaces. The resulting materials are intended to combine the good biocompatible properties of PEO with the outstanding mechanical properties of PTFE. The star-shaped PEOs were synthesized via anionic polymerization. 3 Mev electron beam irradiation was applied to graft these PEO stars onto porous EXPTFE surfaces. The hydrophobic EXPTFE surface had to be pre-modified with N-vinylpyrrolidone. ESCA was used to quantify the amount of grafted star-shaped PEO. Unmodified EXPTFE surfaces are well known, when implanted in a body, to be rapidly covered by a layer of cells and fibrin. The EXPTFE coated with PEO were implanted in the peritoneal cavity of rats (or under the back skin). This implantation did not induce any inflammation reactions and SEM analysis had attested the absence of adsorbed cells and fibrin. The glucose diffusion properties of these membranes were studied by a lag time analysis method and compared to those of pure PEO hydrogels. As expected, glucose diffuses through the hydrogel coated membrane and diffusion is not affected by the presence of the EXPTFE membrane.     

Phase morphology of hydrolysable polyurethanes derived from aqueous dispersions

Biodegradable polyurethanes are an interesting alternative to many applications that involve plastics since they can minimize environmental problems caused by the low rates of natural degradation of synthetic polymers. In addition, since waterborne polyurethanes are based on aqueous dispersions, they restrict the use of organic solvents during processing and application of the polymer, thus contributing furthermore to reduce environmental damage. In this work, aqueous anionic polyurethane dispersions (PUD) with tailorable susceptibility for hydrolysis were synthesized by progressively replacing polypropylene glycol (PPG) with a biodegradable polycaprolactone diol (PCL) as soft segments. The hard segments were formed by extending isophorone diisocyanate (IPDI) with hydrazine (HZ). Dimethylol propionic acid (DMPA) was used as ionic center and triethyl amine (TEA) as neutralizer. The degree of phase separation was evaluated mainly by infrared spectroscopy (FTIR) and small angle X-ray scattering (SAXS). The results indicated that phase separation between hard and soft segments of poly(ester-urethane) is more significant than that of poly(ether-urethane). Data obtained from SAXS experiments indicated that phase separation within soft domains can also be present in samples containing both polyester and polyether soft segments. Hydrolytic degradation of the polymers in buffer solution of pH 7.4 and alkaline solution was performed as an initial test. The results showed that the fraction of polyester soft segments in the polyurethanes can be used to tailor the susceptibility of the materials to hydrolytic attack. Polyurethanes having higher contents of polyester were more promptly hydrolytically degraded than polyurethanes containing only polyether segments.     

Adhesion properties of a silicon-containing calcium phosphate coating deposited by RF magnetron sputtering on a heated substrate

Silicon-containing hydroxyapatite coatings 400–700 nm in thickness are prepared by means of radio-frequency (RF) magnetron sputtering on a heated (to 200°C) titanium substrate chemically etched and treated with a pulsed electron beam. The morphology and phase composition of the coating are studied. The morphology and roughness of the composite “calcium-phosphate coating-titanium substrate” differ depending on the treatment procedure of the substrate before deposition. The scratch test method is used to assess the adhesion strength of the coatings formed at different values of bias potential applied to the substrate. It is observed that the adhesion strength of the coating changes with decreasing crystallite size.     

New Applications of the Lithiated Phosphinimine Ph3P=N-Li: Synthesis of α,β-Unsaturated Nitriles and P=N-P Linked Phosphinimines

Abstract

The reaction of Ph₃P-N-Li⁽¹²⁾ with various α,β-unsaturated esters gives access to new N-(α,β-unsaturated acyl) phosphinimines. which can undergo intramolecular aza-Wittig reaction (at 65 - 110°C) to afford the corresponding nitriles.