Determination of Tributyltin in Oysters by Electrothermal Atomic Absorption Spectrometry

Abstract

Graphite-furnace atomic absorption spectrometry for tributyltin in oysters is described. Tributyltin is extracted by n-hexane after digestion with hydrochloric acid. The 3[sgrave] detection limit for tributyltin is better than 0.01 mg Sn/kg. Typical absorbance values are about 0.10 for tributyltin contents as low as 0.03 mg Sn/kg. Tributyltin contents of 29 oyster samples are given.     

Synthesis and structural characterization of tris (methacrylato)chromium(III)

A straightforward synthetic route to produce tris(methacrylato)chromium(III), Cr(O₂C(CH₃)C=CH₂)₃, by reacting sodium methacrylate with an aqueous solution of CrCl₃ gave a blue microcrystalline powder, insoluble in most common solvents. Electronic spectroscopy (UV-Vis), electron paramagnetic resonance (EPR), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), were employed to characterize Cr(O₂C(CH₃)C=CH₂)₃. Morphology and elemental composition of this compound were determined using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX), respectively. Spherical particles of approximately 2.5 µm in diameter were obtained. Thermal stability of the product was investigated via thermogravimetric analysis (TGA). The spectroscopic studies revealed that the coordination sphere around the chromium ion corresponds to a chelating bidentate carboxylate-Cr(III) complex. Thermal stability above 350°C, and spherical shape particles of few micrometers in diameter, suggest a potential application of this novel compound as a catalyst in oxidation reactions.     

Synthesis of precursors of poly(acryl amides) by copper mediated living radical polymerization in DMSO

The paper describes the optimization of copper(I) mediated living radical polymerization of N-hydroxysuccinimide methacrylate to achieve AB block copoly(acryl amides) offering a route to polymers with potential biomedical applications. Polymerization of N-hydroxysuccinimide methacrylate was carried out using copper(I) bromide/N-(n-propyl)-2-pyridylmethanimine catalyst with ethyl-2-bromoisobutyrate as the initiator at three different temperatures (70, 50 and 30 °C). Polymerizations at both 70 and 50 °C gave relatively high conversion, 72% and 62% respectively after 4 h. Polymerization at 30 °C the best linear first-order kinetic plot. The polydispersity remained narrow (1.15) and there was a good agreement between experimental, determined by ¹H NMR, and theoretical M_n. Polymerization of N-hydroxysuccinimide methacrylate was investigated in more detail by following reactions in situ by ¹H NMR. The experimental values of M_n (NMR) were quite close to the theoretical values and the polydispersities were relatively narrow (1.10-1.19). Isolated poly(N-hydroxysuccinimide methacrylate) was used as a macroinitiator for the polymerization of MMA catalyzed by Cu(I)Br in conjunction with N-(n-propyl)-2-pyridylmethanamine ligand leading to block copolymers. A poly(methyl acryl amide) is synthesized indirectly from the reaction of benzyl amine with poly(N-hydroxysuccinimide methacrylate) for 5 h with in DMSO at 50 °C under nitrogen.     

UV-curable coatings of highly crosslinked trimethylmelamine based acrylates and methacrylates

The synthesis and characterization of N¹,N²,N³-trimethylmelamine based (meth)acrylates and their application as components of UV-curable lacquers is described. A pre-condensed oligomeric mixture with a degree of condensation up to five is obtained via a one-pot conversion. Dividing the synthesis into two steps gives access to the mostly monomeric tris(meth)acrylates in overall yields higher than 76%. In general, the prepared compounds can easily be applied on glass, metal, and polystyrene glass affording highly transparent, hard, and scratch resistant coatings after UV-curing. The UV-cured monomeric trimethylmelamine trisacrylate was fully characterized by means of hardness, gloss, scratch-, abrasion-, and chemical resistance. Remarkably, the trimethylmelamine trisacrylate does not release cancerogen formaldehyde even at 150 °C.     

Thermal Functional Polymeric “Iniferters” Based on Phosphorus-Containing Poly(Thiuram Disulfides); Synthesis and Characterization

Secondary amine end-terminated oligomeric poly(phosphonamides) and poly(phosphorylamides) were synthesized by the condensation reaction of phenylphosphonic dichloride, ethyl dichlorophosphate, 2,2,2-tribromoethyl dichlorophosphate, and 2,2,2-trichloroethyl dichlorophosphate with an excess of piperazine or N,N′-dimethyl-1,6-hexanediamine. The macrodiamines were chain extended by reaction with CS₂ to the macrobis(dithiocarbamates) followed by oxidative coupling to the corresponding poly(thiuram disulfides) bearing the phosphorus functions. The diamine precursors and their polythiuram disuffides were characterized by elemental analysis, spectral analysis, thermal analysis, and viscosity measurements. The thermal stabilities of the prepolymers were correlated with their structures. The composition of the thiuram disulfide functions could be determined by TGA, whereas the kinetics of their thermal decomposition in the solid state was studied by DSC analysis. The activation energy varied with the chemical structure of the backbone but was quite independent of the chain length. Alternatively, oligomeric polythiuram disulfides containing phenyl phosphonate groups were synthesized by the condensation reaction of phenylphosphonic dichloride with N,N′-diethyl-N,N′-bis(2-hydroxyethyl)thiuram disulfide.     

SYNTHESIS,CHARACTERIZATION, AND POLYMERIZATION OF NEW METHACRYLATE ESTERS HAVING PENDANT AMIDE MOIETIES

ABSTRACT

In this paper, the synthesis of a number of new methacrylate esters containing amide group are described. The monomers produced from the reaction of corresponding α-chloro-N-aryl or -N-alkyl acetamides with sodium methacrylate were polymerized with AIBN as initiator. The monomers and their polymers were characterized by IR, ¹H- and ¹³C-NMR spectroscopy. The glass transition temperature and thermal decomposition temperature of the polymers were investigated by DSC-50 and TGA-50 thermobalance, respectively. The photocrosslinking properties of the polymers were also discussed.     

Graft Copolymerization of 2-Hydroxyethyl Methacrylate onto Bovine Serum Albumin: Preparation and Characterization

ABSTRACT

Bovine Serum Albumin (BSA) was separated from the whole blood of freshly slaughtered animals. This BSA was graft copo-lymerized with poly (2-hydroxyethyl methacrylate) and characterized. The infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and percentage of grafting of the composites were studied. The graft copolymers have better physico-chemical properties and, therefore, could be more useful in their field of application.     

Comparison of Stereoselectivity of Intramolecular Cyclization of Aldehydes Tethered with Conjugated Esters Induced by O-Stannyl and O-Samarium Ketyls to Form the Tetrahydrofuran Ring Systems

Several (E)- and (Z)-ω-formyl-5-oxa-2-substituted-α,β-unsaturated esters ( 6Za-6Zc; 6Ea-6Ec; 6Eb′-6Ec′; 6Zb′-6Zc′ ) were prepared in high yields. They were subjected to cyclization of their intramolecular ketyl radicals induced by either samarium(II) iodide or tributyltin hydride. These two reagents gave distinct stereoselectivities. More bicylic lactone than monocyclic hydroxy-ester was formed when tributyltin hydride was used, but the opposite stereoselectivity was obtained when samarium(II) iodide was used. The effect of double-bond configuration, heteroatom and substituent on stereoselectivity is described.     

Analyzing physical characteristics and shielding efficiency for non-lead medical radiation shielding sheets improved using PMMA

ABSTRACT

Recently, the research for replacing heavy lead goods, such as medical radiation shielding sheets with environmentally friendly shielding materials has been widely carried out. The use of tungsten injected into the base material of polyethylene resin may be a good alternative for manufacturing lightweight shielding sheets. However, the increase of the mass ratio of tungsten in the shielding sheets is accompanied by the degradation of their physical properties such as tensile strength and flexibility. In this report, we have tried to fix this problem by adding Polymethyl Methacrylate (PMMA) to the mixing process of materials. If the portion of the added PMMA is 20%, it leads to a 25% increase of the particle packing ratio while there is a simultaneous 28% enhancement of tensile strength compared to before adding it. In the final test for shielding efficiency, it also turned out that the increase of the particle packing ratio for tungsten exhibits the same shielding efficiency as that of 0.2?mmPb. This consequence may imply that mass production of sheets that can prevent scattering rays in the medical radiation frequency range is possible through the calender process using a 0.3?mm tungsten sheet.