Showing papers in "Applied Organometallic Chemistry in 1997"
TL;DR: A countrywide survey and laboratory experiments on imposex in Japanese sea snails were carried out as discussed by the authors, where 38 species were observed to be affected by imposex: Thais clavigera, the percentage occurrence of imposex was 100% at almost all sites surveyed.
Abstract: A country-wide survey and laboratory experiments on imposex (a superimposition of male sex organs on female sea snails) in Japanese sea snails were carried out: 38 species were observed to be affected by imposex. For the rock shell, Thais clavigera, the percentage occurrence of imposex was 100% at almost all sites surveyed. The degree of imposex seemed to be positively correlated with the concentrations of tributyltin (TBT) and triphenyltin (TPT) in the species. The results of laboratory experiments showed that imposex in T. clavigera was initiated and promoted by both TBT and TPT. Many oviduct-blocked individuals, which were thought to be sterile, were observed in T. clavigera at sites near marinas and harbours. The effects of organotin pollution on the population of T. clavigera were observed at the sites near marinas. From the results of the additional country-wide survey on imposex in T. clavigera during 1993–1995, serious organotin pollution and imposex symptoms in the species are still continuing in Japan. © 1997 by John Wiley & Sons, Ltd.
142 citations
TL;DR: An attempt has been made to prove the structures of the resulting complexes on the basis of elemental analyses, conductance measurements and electronic, IR, multinuclear magnetic resonance studies.
Abstract: Equimolar reactions of dibutyltin(IV) oxide with Schiff bases derived from amino-acids led to the formation of a new series of dibutyltin(IV) complexes of general formula, Bu2SnL [L=dianion of tridentate Schiff bases derived from the condensation of 2-hydroxy-1-naphthaldehyde or acetyl acetone with glycine (L-1), L-β-alanine (L-2), DL-valine (L-3), DL-4-aminobutyric acid (L-4), L-methionine (L-5), L-leucine (L-6) and phenylglycine (L-7)]. An attempt has been made to prove the structures of the resulting complexes on the basis of elemental analyses, conductance measurements and electronic, IR, multinuclear magnetic resonance (1H, 13C and 117Sn) and 119Sn Mossbauer spectral studies. The complexes have been tested against various bacteria [Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus penicillin resistance (2500 units)] and fungi (Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii,Trichophyton mentagrophytes and Aspergillus fumigatus). All the complexes showed moderate activity. The cytotoxicity of a few compounds has been screened in vitro against seven human tumour cell lines, viz. MCF-7, EVSA-T, WiDr, IGROV, M19 MEL, A498 and H226. The activities found experimentally were better than those obtained for cisplatin and carboplatin © 1997 John Wiley & Sons, Ltd.
126 citations
TL;DR: In this paper, the chemical forms of arsenic in some herbivorous or mainly marine animals and, in some cases, the algae on which they feed were determined by HPLC-ICP MS.
Abstract: The chemical forms of arsenic in some herbivorous or mainly herbivorous marine animals and, in some cases, the algae on which they feed were determined by HPLC-ICP MS. In most cases arsenobetaine was present in the animals as well as arsenosugars consumed directly from the algae. However in the case of copepods Gladioferens imparipes fed only on the diatom Chaetoceros concavicornis which had been grown in axenic culture, arseno-betaine was absent. Arsenobetaine was also absent from the muscle of the silver drummer Kyphosus sydneyanus, although trimethyl-arsine oxide was present. This is the first reported case of the absence of arsenobetaine in a marine teleost fish and may be related to its fermentative faculty for digesting the macroalgae that it consumes. © 1997 by John Wiley & Sons, Ltd.
110 citations
TL;DR: In this paper, the arsenic species present in a range of commercially available dried-algal food products were characterized by HPLC-ICP-MS, and only 34% of the extracted arsenosugars were extractable.
Abstract: The arsenic species present in a range of commercially available dried-algal food products were characterized by HPLC–ICP–MS. The products of marine origin contain up to four dimethylarsinylribosides (1) in the 8–49 ppm range and some also contain dimethylarsinic acid (DMAA). These species are easily extracted and account for most of the arsenic burden. One sample of a freshwater alga Nostoc sp. was found to contain a lower concentration of arsenic, 3 ppm, and only 34% of this was extractable. The extract representing 1 ppm of arsenic contained one of the arsenosugars 1 found in the marine samples (93%), the rest being DMAA. This is the first report of the identification of an arsenosugar from an organism of terrestrial origin. The implications of this result in connection with the global arsenic cycle are discussed. © 1997 John Wiley & Sons, Ltd.
87 citations
TL;DR: In this article, the main arsenic compound found in many mushrooms (various puffballs, Agaricales and Aphyllophorales) was arsenobetaine.
Abstract: In 50 mushroom species (56 samples) from Slovenia, Switzerland, Brazil, Sweden, The Netherlands and USA, total arsenic was determined by radiochemical neutron activation analysis (RNAA). Arsenic concentrations ranged from 0.1 to 30 μg g−1 (dry mass). Arsenic compounds were determined in methanol extracts from the mushrooms by HPLC–ICP–MS. The aim of the study was not only to quantify arsenic compounds in mushrooms but also to uncover trends relating the methylating ability of a mushroom to its taxonomic or evolutionary status.
The main arsenic compound found in many mushrooms (various puffballs, Agaricales and Aphyllophorales) was arsenobetaine. Arsenate [As(V)] was the main arsenic species in Laccaria fraterna and Entoloma rhodopolium and arsenite [As(III)] in Tricholoma sulphureum. A mixture of arsenite and arsenate was present in Amanita caesarea. Dimethylarsinic acid (DMA) and methylarsonic acid were present in many mushrooms, but generally as minor components. In Laccaria laccata, Leucocoprinus badhamii and Volvariella volvacea, DMA was the major metabolite. Arsenocholine (AC) and the tetramethylarsonium ion were present in a few species, generally at low concentrations, except for Sparassis crispa, in which AC was the main compound. Tri- methylarsine oxide was not found in any of the mushrooms. In some species small amounts of unknown compounds were also present. The possible taxonomic significance of the metabolite patterns and the predominance of arsenobetaine in more advanced fungal types are discussed. © 1997 John Wiley & Sons, Ltd.
80 citations
TL;DR: In this paper, a review of polysilane and related copolymer synthesis reactions is presented, where the Lewis-base catalyzed disproportionation mechanism is discussed and seems to involve donor-stabilized silylenes as key intermediates in the polymer formation process.
Abstract: Tailoring of polysilanes with given architectures and reactivities is a great challenge in the field of SiC pre-ceramic polymers. This paper reviews recent polysilane and related copolymer synthesis reactions.
It is shown that the Wurtz-type polymerization of dichloro-, trichloro- or tetrachloro-silanes, so far the most extensively studied, enables access to a large variety of architectures ranging from one- to three-dimensional (3D) topologies, and based on secondary >SiR2, tertiary RSi(Si)3 or quaternary Si(Si)4 silicon units in the polymer backbone. These polysilanes usually present an intrinsic low reactivity, detrimental for fiber processing. Examples are given to illustrate how this reactivity can be increased by secondary substitution reactions, which create reactive entities that can favor further crosslinking reactions.
Secondly a novel route involving heterogeneously catalyzed disproportionation of chloromethyldisilanes, developed in our laboratory, is reviewed which offers a direct access to polysilyne-type 3D architecture constituted by arrangements of fused rings. The Lewis-base catalyzed disproportionation mechanism is discussed and seems to involve donor-stabilized silylenes as key intermediates in the polymer formation process. The experimental results are supported by ab-initio quantum chemical calculations.
Silylenes attack the Si sites of higher functionality causing a high regioselectivity for the exclusive formation of branched oligosilanes. The oligomers undergo thermally induced branching and crosslinking reactions leading to poly(chloromethylsilane)s. Obviously, there are analogies to the oligomer and polymer formation of the transition-metal complex catalyzed dehydropolymerzation of methyldisilanes. Poly(chloromethylsilane)s exhibit a high reactivity due to the presence of Si–Cl bonds.
Disproportionation of chloromethyldisilanes in presence of olefins such as styrene provides promising polymer precursors for SiC fibers. Their rheological properties have been investigated for various styrene contents. The polymer fibers spun from melt are cured under ammonia, and then pyrolyzed to silicon carbide fibers, showing temperature resistance up to 1500 °C. © 1996 by John Wiley & Sons, Ltd.
79 citations
TL;DR: In this paper, the synthesis of silazane-based polymers for processing fiber-reinforced ceramic matrix composites (CMCs) was investigated. But the main focus was on the optimization of the precursors for CMCs.
Abstract: The goal of this investigation was to optimize the synthesis of silazane-based polymers for processing fibre-reinforced ceramic matrix composites (CMCs). Liquid oligomeric silazanes were synthesized by ammonolysis of chlorosilanes and characterized spectroscopi- cally (FTIR, NMR) as well as by elemental analysis. The silazanes were obtained in high yield and purity. Different functional groups (system S1: Si—H, Si—CH3, Si—CH=CH2) and different degrees of branching in the Si—N backbone [system S2; Si(NH)3, Si(NH)2] were realized in order to study the properties of the silazanes that are dependent on the molecular structure.
For processing ceramics via pyrolysis of pre-ceramic oligomers, molecular weight, rheological behaviour, thermosetting and ceramic yield were investigated systematically and correlated with the molecular structure of the silazanes. Low molecular weights (500–1000 g mol−1) as well as low viscosity values (0.1–20 Pa s) enable processing of the silazanes in the liquid phase without any solvent. Due to the latent reactivity of the functional groups, curing of the polymers via hydrosilylation is achieved.
Structural changes and weight loss during polymer curing as well as the organic/inorganic transition were monitored by FTIR spectroscopy and differential thermogravimetric analysis. With increasing temperature (room temperature to 800 °C) the hydrogen content decreases from 7 to < 0.5 wt% due to the formation of gaseous molecules (NH3, CH4, H2). High ceramic yields up to 80% were reached by branching the oligomers, thus reducing the amount of volatile precursor fragments.
Up to 1300 °C, ceramic materials remained amorphous to X-rays. At higher temperatures (1400–1800 °C) either SiC or SiC/Si3N4 composites were selectively crystallized, depending on the pyrolysis conditions. The utility of the optimized precursors for CMCs has been demonstrated by infiltration of fibre preforms and subsequent pyrolysis. © 1997 by John Wiley & Sons, Ltd.
73 citations
TL;DR: Arsenic circulation in an arsenic-rich freshwater ecosystem was elucidated to detect arsenic species in the river water and in biological samples living in the freshwater environment as mentioned in this paper, using a hydride generation/cold trap/cryofocus/gas chromatography-mass spectrometry (HG/CT/CF/GC-MS) system.
Abstract: Arsenic circulation in an arsenic-rich freshwater ecosystem was elucidated to detect arsenic species in the river water and in biological samples living in the freshwater environment. Water-soluble arsenic compounds in biological samples were extracted with 70% methanol. Samples containing arsenic compounds in the extracts were treated with 2 mol dm3 of sodium hydroxide and reduced with sodium borohydride. The detection of arsenic species was accomplished using a hydride generation/cold trap/cryofocus/gas chromatography-mass spectrometry (HG/CT/CF/GC-MS) system. The major arsenic species in the river water, freshwater algae and fish are inorganic arsenic, dimethylarsenic and trimethylarsenic compounds, respectively. Trimethylarsenic compounds are also detected in aquatic macro-invertebrates. The freshwater unicellular alga Chlorella vulgaris, in a growth medium containing arsenate, accumulated arsenic and converted it to a dimethylarsenic compound. The water flea Daphnia magna, which was fed on arsenic-containing algae, converted it to a trimethylarsenic species. © 1997 by John Wiley & Sons, Ltd.
65 citations
TL;DR: In this article, the arsenic compounds extracted with methanol/water (9:1) from the dried mushroom powders were separated by HPLC on anion-exchange and reversed phase columns and detected by ICP-MS using a hydraulic high-pressure nebulizer.
Abstract: Three mushroom species from two old arsenic smelter sites in Austria were analyzed for arsenic compounds. The total arsenic concentrations were determined by ICP–MS. Collybia maculata contained 30.0 mg, Collybia butyracea 10.9 mg and Amanita muscaria 21.9 mg As kg−1 dry mass. The arsenic compounds extracted with methanol/water (9:1) from the dried mushroom powders were separated by HPLC on anion-exchange and reversed-phase columns and detected by ICP-MS using a hydraulic high-pressure nebulizer. In Collybia maculata almost all arsenic is present as arsenobetaine. Collybia butyracea contained mainly arsenobetaine (8.8 mg As kg−1 dry mass) and dimethylarsinic acid (1.9 mg As kg−1). Amanita muscaria contained arsenobetaine (15.1 mg As kg−1), traces of arsenite, dimethylarsinic acid and arsenate, and surprisingly arsenocholine (2.6 mg As kg−1) and a tetramethylarsonium salt (0.8 mg As kg−1). © 1997 by John Wiley & Sons, Ltd.
65 citations
TL;DR: In this paper, two approaches which have shown promising results for producing useful materials for photonics are described: (i) a novel way to fabricate organically doped, multiphasic nanostructured composite monoliths and (ii) a method of fabrication of organically-doped, sol-gel-derived optical fibers.
Abstract: Sol-gel-processed organic-inorganic hybrid materials combine the merits of inorganic glass and organic molecules, and are therefore a class of materials with good potential for photonics. In this review, two approaches which have shown promising results for producing useful materials for photonics are described: (i) a novel way to fabricate organically doped, multiphasic nanostructured composite monoliths and (ii) a method of fabrication of organically doped, sol-gel-derived optical fibers. For each approach, the preparation process is presented, together with selected applications such as multidye solid-state tunable laser, multiphasic optical power limiter, a micron-scale chemical-sensing and biosensing fibers and solid-state dye-doped fiber lasers.
64 citations
TL;DR: A solid phase extraction method using a phenyl-bonded silica sorbent was developed for the isolation of mono- and di-methyltin, -butyltin and -octyltin from drinking water.
Abstract: A solid-phase extraction method, using a phenyl-bonded silica sorbent, was developed for the isolation of mono- and di-methyltin, -butyltin and -octyltin from drinking water. Recoveries averaged 92% over two tested sample weights and spiking levels. Ethyl derivatives were made by Grignard reaction for determination by gas chromatography–atomic absorption spectrometry (GC–AAS). Static and repetitive extraction studies were conducted at 24 and 65°C. Butyltins rapidly leached into drinking water kept in chlorinated poly(vinyl chloride) (CVPC) pipe samples. Monobutyltin and dibutyltin levels reached 19.8 (13.4 as Sn) and 197 (100.4 as Sn) ng g−1 respectively in water samples collected from CPVC pipe heated to 65°C. Butyltins were still leached from CPVC pipe after 20 repetitive extractions, suggesting that new CPVC water systems would contaminate water with organotins for some time after installation. © 1997 John Wiley & Sons, Ltd.
TL;DR: A simple and fast synthesis of radioactive methylmercury is presented in this paper, based on the methylation of inorganic 203Hg(II) by methylcobalamin and isolation of resulting CH3203Hg (II) in a single extraction step.
Abstract: A simple and fast synthesis of radioactive methylmercury is presented. It is based on the methylation of inorganic 203Hg(II) by methylcobalamin and isolation of resulting CH3203Hg(II) in a single extraction step. Time required is less than 4 hours and the final yield is ⩾90%. © 1997 John Wiley & Sons, Ltd.
TL;DR: In this paper, an organic and an inorganic salt of antimony were reduced and methylated biologically by microorganisms in laboratory experiments and the organoantimony compound produced was trimethylstibine [(CH3)3Sb] and was detected in a culture headspace.
Abstract: We have evidence that an organic and an inorganic salt of antimony were reduced and methylated biologically by microorganisms in laboratory experiments. The organoantimony compound produced was trimethylstibine [(CH3)3Sb] and was detected in a culture headspace. This was confirmed by matching the compound's retention time in capillary gas chromatography, as detected by fluorine-induced chemiluminescence, with a com- mercial standard and by its mass spectrum determined with gas chromatography/ mass spectrometry (GC–MS). (CH3)3Sb was detected in the headspace of soil samples amended with either potassium antimonyltartrate or potassium hexahydroxyantimonate and augmented with any one of three different nitrate-containing growth media. The identity of the microorganisms in soil that accomplished this are as yet unknown. Of 48 soil samples amended with these two compounds, 24 produced trimethylstibine. Bioreduction of trimethyldibromoantimony was also detected in a liquid monoculture of Pseudomonas fluorescens K27 which also produced tri- methylstibine. This headspace production of (CH3)3Sb was determined to be linked to the culture's cell population as measured by optical density. This microbe, however, did not biomethylate either potassium antimonyltartrate or potassium hexahydroxyantimonate in any experiments we performed. © 1997 John Wiley & Sons, Ltd.
TL;DR: In this paper, butyltin compounds (mono-, di-, and tri-butyltin) were determined in dolphin (Platanista gangetica), fish, invertebrates and sediment collected from the River Ganges, India, in order to understand the contamination levels, sources, and potential for biomagnification in freshwater food chains.
Abstract: Concentrations of butyltin compounds (mono-, di-, and tri-butyltin) were determined in dolphin (Platanista gangetica), fish, invertebrates and sediment collected from the River Ganges, India, in order to understand the contamination levels, sources, and potential for biomagnification in freshwater food chains. Total butyltin concentration in dolphin tissues was up to 2000 ng g 2 1 wet wt, which was about 5‐10 times higher than in their diet. The concentrations in fish and benthic invertebrates, including polychaetes, were 3‐10 times greater than in sediment. The biomagnification factor for butyltins in river dolphin from its food was in the range 0.2‐7.5. Butyltin concentrations in Ganges river organisms were higher than those reported for several persistent organochlorine compounds. Discharge of untreated domestic sewage was one of the major sources of butyltin residues in Ganges river biota. High concentrations of butyltin compounds in freshwater food chains suggest the need to assess their toxic effects in aquatic organisms and to regulate their use. © 1997 by John Wiley & Sons, Ltd.
TL;DR: In this paper, a polymeric organosilicon gel with the composition [MeSi(NCN)1.5]n synthesized by the reaction of MeSiCl3 with Me3Si−N=C=N-SiMe3 is reported.
Abstract: A novel polymeric organosilicon gel with the composition [MeSi(NCN)1.5]n synthesized by the reaction of MeSiCl3 with Me3Si–N=C=N–SiMe3 is reported. The reaction is performed without any solvent and with catalytic amounts of pyridine and provides highly cross-linked poly(methylsilsesquicarbodi-imide) in the form of a stable non-oxidic gel with unusual low open porosity (<1 m2 g−1). The Si–C–N gel transforms to an amorphous silicon carbonitride ceramic, SiC1.1N1.6, by the thermally induced ceramization at 1200 °C in inert atmosphere (argon). The gel-derived silicon carbonitride is thermally stable up to 1450 °C. The synthesis, characterization and pyrolysis behavior of the new polyorganosilicon gel is discussed. © 1997 John Wiley & Sons, Ltd.
TL;DR: In this article, butyltin compounds (BTCs) including mono-MBT, di-(DBT), and tri-butyltin (TBT) were detected in the liver of a porpoise collected in the semi-closed sea.
Abstract: Although organotins are notorious man-made organometallic species introduced into the aquatic environment, no investigation had been concerned with contamination of higher trophic animals such as marine mammals until the last few years. Our recent work demonstrated the detection of butyltin compounds (BTCs), including mono- (MBT), di-(DBT), and tri-butyltin (TBT) in marine mammals. This paper reviews BTC contamination in higher trophic animals, based on our recent publications. Analysis for BTCs showed significant accumulation in tissues and organs of three finless porpoises (Neophocaena phocaenoides) collected from Japanese coastal waters. More than 10 μg of butyltin ions per gram on a wet weight basis were detected in the liver of a porpoise collected in the semi-closed sea. Distribution of BTCs in the tissues and organs of the porpoises showed a similar pattern to several other marine mammal species: higher concentrations in liver and kidney, and lower in muscle and blubber. In addition, tissues and organs from two water birds and one sea turtle species were also analyzed for BTCs, and their concentrations and compositions were compared among the species. The results showed that the distribution of these contaminants extends widely, not only to marine mammals but also to other higher trophic species. On the other hand, the composition of the BTCs exhibited a specific profile in each species. The ratios of hepatic concentrations of DBT or MBT to TBT for marine mammals were relatively lower than those of water birds and the sea turtle, indicating that metabolism and excretion of TBT may be less efficient in the mammalian species. © 1997 by John Wiley & Sons, Ltd.
TL;DR: In this article, the performance of heterogeneous catalysts based on surfactant-stabilized palladium colloids is compared with conventional Pd/C and Lindlar catalysts in the partial hydrogenation of 3-hexyn-1-ol under optimized reaction conditions.
Abstract: The performance of heterogeneous catalysts based on surfactant-stabilized palladium colloids is compared with conventional Pd/C and Lindlar catalysts in the partial hydrogenation of 3-hexyn-1-ol under optimized reaction conditions. The selectivity can be influenced by the protective shell as well as by the support and various promoters. The zwitterionic surfactant sulfobetaine-12 (N,N-dimethyldodecylammoniopropanesulfonate) appears to be best suited as a protective shell for highly selective palladium-colloid catalysts under the surfactants tested. The preferred support is CaCO3: the Pd(SB12) colloids supported on CaCO3 show the highest selectivities and activities of all tested catalysts. The best selectivity (98.1%) towards the desired cis-3-hexen-1-ol (leaf alcohol) is obtained with a lead-promoted palladium colloid supported on CaCO3. This catalyst is slightly (0.5%) better in selectivity and twice as active as a conventional Lindlar catalyst. © 1997 John Wiley & Sons, Ltd.
TL;DR: In this article, an attempt is made to classify transparent organic/inorganic materials synthesized by the sol-gel process and the chemical structures of the hybrids are the main criteria for this classification.
Abstract: An attempt is made to classify transparent organic/inorganic materials synthesized by the sol–gel process. The chemical structures of the hybrids are the main criteria for this classification. Three main types of organic/inorganic gels are distinguished and their basic physico-chemical characteristics are outlined. © 1997 by John Wiley & Sons, Ltd.
TL;DR: In this paper, the surface tension of defined siloxanes as well as those of analogous carbosilanes, polysilanes and neopentyl substituted silanes were determined.
Abstract: The surface tensions, wetting tensions, contact angles and solid/liquid interfacial tensions of defined siloxanes as well as those of analogous carbosilanes, polysilanes and neopentyl substituted silanes were determined. The wetting experiments were carried out on a glass plate coated with perfluoroalkyl methacrylate (FC 722®). The siloxanes possess the lowest surface tensions. Due to the presence of oxygen atoms in the siloxane backbone, a donor–acceptor portion (γ+/−lv) of the surface tension of about 1–2 mN/m was determined. The solid/liquid interfacial tension also contains a donor–acceptor portion (γ+/−sl). Its value is almost identical to that of γ+/−lv. The γ+/−sl differences between individual molecules of the same surface tension are responsible for contact angle differences of up to 4°. © 1997 John Wiley & Sons, Ltd.
TL;DR: Bis(dicyclohexylammonium) bis(2,6-pyridine-dicarboxylato)dibutylstannate is assigned sevenfold coordination at tin on the basis of its ll 9 Sn CP/MAS NMR chemical shift (δ=-424.9 ppm) as mentioned in this paper.
Abstract: Bis(dicyclohexylammonium) bis(2,6-pyridine-dicarboxylato)dibutylstannate is assigned seven-fold coordination at tin on the basis of its ll9 Sn CP/MAS NMR chemical shift (δ=-424.9 ppm). The assignment has been corroborated by a crystal structure determination of its monohydrate, whose tin atom has the trans-C 2 SnNO 4 pentagonal bipyramidal [Sn-C=2.040(9), 2.067(8) A; C-Sn-C =168.9(5)°] geometry. One 2,6-pyridine-dicarboxylato group chelates to the tin atom (Sn-O=2.234(4), 2.260(4); Sn-N = 2.279(5) A) whereas the other binds through only one carboxyl -C0 2 end (Sn-O=2.416(5), 2.441(5)A). Hydrogen bonds link the cation and the stannate into a linear chain parallel to the b-axis. The lattice water molecule is hydrogen-bonded to the free carboxyl end. The anhydrous compound showed higher in vitro antitumor activity than those of carboplatin and cisplatin when screened against breast (MCF-7, EVSAT), colonic (WiDr), ovarian (IGROV) and renal (A498) carcinoma, and melanoma (M19 MEL) cell lines.
TL;DR: Arsenic compounds were identified and quantified in the mushroom Amanita muscaria, collected close to a facility that had roasted arsenic ores as mentioned in this paper, using an ICP-MS detector equipped with a hydraulic high-pressure nebulizer.
Abstract: Arsenic compounds were identified and quantified in the mushroom Amanita muscaria, collected close to a facility that had roasted arsenic ores. The powdered dried mushrooms were extracted with methanol/water (9:1), the extracts were concentrated and the concentrates were dissolved in water. The resulting solutions were chromatographed on anion-exchange, cation-exchange and reversed- phase columns. Arsenic was detected on-line with an ICP–MS detector equipped with a hydraulic high-pressure nebulizer. Arsenite, arsenate, dimethylarsinic acid and the tetramethylarsonium cation were minor arsenic compounds (∼2% each of the total 22 mg kg−1 dry mass), and arsenobetaine, arsenocholine (∼15% each) and several unidentified arsenic compounds (∼60%) were the major arsenic compounds in Amanita muscaria. The presence of arsenocholine (detected for the first time in a terrestrial sample) was ascertained by matching retention times in the anion-exchange, cation- exchange and reversed-phase chromatograms with the retention time of synthetic arsenocholine bromide and chromatographing extracts spiked with arsenocholine bromide. © 1997 John Wiley & Sons, Ltd.
TL;DR: The presence of the highly toxic antifouling agent tributyltin (TBT) and its degradation products was determined in four species of mussels collected from 34 locations in fresh water in Ontario and in sea water on Canada's west and east coasts as mentioned in this paper.
Abstract: The presence of the highly toxic antifouling agent tributyltin (TBT) and its degradation products was determined in four species of mussels collected from 34 locations in fresh water in Ontario and in sea water on Canada's west and east coasts. The purpose of the study was to establish baseline information in order to assess TBT trends in mussels after the 1989 Canadian regulation of antifouling uses of TBT. In fresh water, concentrations of TBT were much higher in zebra mussels (Dreissena polymorpha) than in Elliptio complanata or Lampsilis radiata radiata. High concentrations of TBT were also found in Mytilus edulus in sea water. Residues of TBT in all species were similar to those that have been determined in other parts of the world before and after the regulation of antifouling uses of TBT in various countries. Analyses for degradation products indicated that zebra mussels metabolize TBT at about the same rate as L. radiata radiata and M. edulis, but more slowly than E. complanata. © 1997 John Wiley & Sons, Ltd.
TL;DR: In this article, a facile preparation of polyimide-silica gel hybrids by the simultaneous in-situ formation polyimides during the hydrolysis-condensation of tetramethoxysilane (TMOS) was carried out in a solution of DMAc containing 5% LiCl, CaCl2 or ZnCl2.
Abstract: A facile preparation of polyimide–silica gel hybrids by the simultaneous in-situ formation of polyimides during the hydrolysis–condensation of tetramethoxysilane (TMOS) is reported here. The hydrolysis and condensation of TMOS was carried out in a solution of DMAc containing 5% LiCl, CaCl2 or ZnCl2 and the seven-membered cyclic polyimide intermediate. The seven-membered cyclic intermediates, precursors of polyimides, were derived from the low-temperature polycondensation of dianhydrides [benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and 4,4-bis(hexafluoroisopropylidene)phthalic dianhydride (6FDA)] and di-isocyanates [isophorone di-isocyanate (IPDI), toluene di-isocyanate (TDI), hexamethylene di-isocyanate (HDI) and 4,4′-diphenylmethane di-isocyanate (MDI)]. These intermediates could readily be converted to the corresponding polyimides. Films were cast from the resulting mixtures and the solvent was gradually evaporated at 130 °C to result in the formation of clear, transparent, pale yellow or amber-colored hybrid films in which the salts were dispersed at the molecular level. Pyrolysis of polyimide–silica gel hybrids at 600 °C gave mesoporous silica. Silica gel obtained from hybrids HPI-8 (containing no salt) and HPI-11 (containing ZnCl2) had a pore radius (BJH method) of 2.9 nm, while that from hybrid HPI-9 (containing LiCl) had a pore radius of 11.4 nm. The surface areas (BET method) obtained were 203 m2 g−1, 19 m2 g−1 and 285 m2 g−1, while the pore volumes were 0.373 cm3 g−1, 0.158 cm3 g−1 and 0.387 cm3 g−1, respectively, for samples obtained from hybrids HPI-8, HPI-9 and HPI-11. © 1997 by John Wiley & Sons, Ltd.
TL;DR: In this paper, the contact angles of aqueous surfactant solutions above the critical micelle formation concentration (cmc) on nonpolar perfluorinated surfaces (FEP® plate) were determined.
Abstract: The siloxanyl-modified carbohydrate surfactants investigated consist of the four structural elements: (1) siloxanyl moiety; (2) spacer; (3) carbohydrate unit; and (4) modifying element. By static surface tension (γ lv σ) and wetting tension (γ sv - γ sb α) measurements the contact angles of aqueous surfactant solutions above the critical micelle formation concentration (cmc) on nonpolar perfluorinated surfaces (FEP® plate) were determined. Although the siloxanyl units were found to have a high capacity to level out the interfacial properties, both surface tension and wetting tension react independently to defined changes in the chemical structure of the surfactant molecules. The results of spreading experiments on polypropylene show good correlation with the dependences found by wetting measurements.
TL;DR: In this paper, seasonal changes in the distribution of arsenic species were observed in a dredged area in the southern basin of Lake Biwa, Japan, and the concentrations of dimethylarsenic acid [DMAA(V)] became comparable with those of inorganic forms during a stratification period.
Abstract: Seasonal changes in the distribution of arsenic species were observed in a dredged area in the southern basin of Lake Biwa, Japan. The concentrations of dimethylarsenic acid [DMAA(V)] became comparable with those of inorganic forms during a stratification period. DMAA(V) increased not only in the photic zone but also in the hypolimnion. In the photic zone, an increase in DMAA(V) was observed with the yearly maximum of water temperature. In the hypolimnion, the seasonal changes in methylarsenicals differed from those in surface waters. DMAA(V) maxima appeared seasonally under sub-anoxic conditions and developed regionally at the redox boundary and above the sediment surface. The DMAA(V) concentrations increased in the initial period of oxygen depletion and just after the disappearance of anoxia, while they diminished in the anoxic hypolimnion by midsummer. The seasonal behavior of trivalent methylarsenicals, which are readily oxidized in oxic environments, was similar to that of DMAA(V). The total arsenic concentration in the surface layer rose to a maximum in late summer. Methylarsenicals did not increase in such a way that the total arsenic concentration increased during summer. © 1997 by John Wiley & Sons, Ltd.
ENEA1
TL;DR: In this paper, two different derivatization methods, alkyla-tion with Grignard reagents, and ethylation with sodium tetraethylborate, were compared for the determination of organotin com-pounds, viz. tributyltin, dibutytin, monobutyltin and triphenyltin.
Abstract: Commission of the European Communities, DG XII, Standards, Measurements, and TestingProgramme, Rue de la Loi 200, 1049 Brussels, BelgiumTwo different derivatization methods, alkyla-tion with Grignard reagents, and ethylationwith sodium tetraethylborate, were comparedfor the determination of organotin com-pounds, viz. tributyltin, dibutyltin,monobutyltin, triphenyltin, diphenyltin andmonophenyltin, in mussel samples. Tempera-ture, reaction time and concentration ofGrignard reagents were optimized in theformer method; in the latter the effect of pH,concentration of sodium tetraethylborate andreaction time were studied. In the derivatiza-tion with Grignard reagents hexyl, pentyl,propyl, ethyl and methyl were used as alkylGrignard groups. A critical evaluation of thedifferent derivatization methods is presented.© 1997 by John Wiley & Sons, Ltd.
TL;DR: Pulsed flame photometric detection (PFPD) for gas chromatography was applied to organotin compounds as standards and in environmental samples as discussed by the authors, and the absolute limit of detection for this capillary GC-PFPD technique ranged from 0.2 to 0.4
Abstract: Pulsed flame photometric detection (PFPD) for gas chromatography was applied to organotin compounds as standards and in environmental samples. Ethylated organotin species (n-propyl-, n-butyl- and phenyl-) were extracted from spiked artificial seawater and from an environmental sample. Selectivity towards tin is shown in the analysis of highly polluted seawater samples from a commercial port where no significant interferences are found. The self-cleaning capability and long-term stability of PFPD is shown in this work during 140 days of continuous operation. The absolute limit of detection for this capillary GC–PFPD technique ranged from 0.2 to 0.4 pg (Sn) for tetraethyl- to tetraphenyl-tin, allowing determination of sub-nanogram/litre concentrations of organotin compounds. © 1997 John Wiley & Sons, Ltd.
TL;DR: In this paper, the growth of Chlorella Bohm, Chlorlla kessleri and chlorella 108 in media containing sodium arsenate at 200 or 2000 mg/As/DM−3 was investigated.
Abstract: The growth of Chlorella Bohm, Chlorella kessleri and Chlorella 108 in media containing sodium arsenate at 200 or 2000 mg As dm−3 was investigated. The cell densities in the stationary phases were 40% higher for Chlorella Bohm (5.6×105 cells cm−3) and Chlorella kessleri (4.5×105 cells cm−3) grown in the 2000 mg As dm−3 arsenate media compared with the arsenic-free media. The growth of Chlorella 108 was depressed by arsenate. Dimethylarsinic acid (at concentrations never exceeding 1.2 mg As dm−3) and arsenite (⪅0.2 mg As dm−3) were detected in the growth medium. The cells harvested during the stationary phase had 2400 mg arsenic associated with 1 kg dry mass. A water/methanol (80:20) mixture extracted all the arsenic from the cells. Most of the arsenic (99%) was arsenate. Arsenite, methylarsonic acid and dimethylarsinic acid accounted for the remaining arsenic. Cadmium in the arsenic-containing growth media (50 μg to 100 mg dm−3) reduced the yield of algal cells and induced the formation of an unidentified arsenic compound in Chlorella Bohm. © 1997 by John Wiley & Sons, Ltd.
TL;DR: In this paper, total arsenic concentrations in freeze-dried pulverized ants (Formica sp.) and material from an ant-hill collected at a former arsenic roasting facility were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion with nitric acid and hydrogen peroxide.
Abstract: Total arsenic concentrations in the freeze-dried pulverized ants (Formica sp.) and material from an ant-hill collected at a former arsenic roasting facility were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion with nitric acid and hydrogen peroxide. The ants contained 12.6 ± 0.9 mg As/kg dry mass, the ant-hill material 5420 ± 90 mg As/kg dry mass. Total arsenic concentrations in needles of Picea abies and Larix decidua (spruce and larch needles) were also determined, because needles are the main constituents of the upper layer of ant-hill material. Needles of Picea abies contained 1.17 mg As/kg dry mass and needles of Larix decidua 3.71 mg As/kg. The Formica sp. and ant-hill material were extracted with water or methanol/water (9:1). The extracts were chromatographed on a cation-exchange and an anion-exchange column. Water extracted 20% of the arsenic from the ants and only 3% from the ant-hill material. With methanol/water (9:1) only 7% of the arsenic was released by the ants and 0.5% by the ant-hill material. The arsenic compounds in the column effluents that were introduced into the plasma via a hydraulic high-pressure nebulizer (HHPN) were quantified on-line by ICP-MS. Arsenite and arsenate were the major arsenic compounds in the extract. Dimethylarsinic acid and traces of methylarsonic acid and arsenobetaine were also detected. The extracts of the ant-hill material contained the same compounds. Additionally, traces of trimethylarsine oxide were found. The presence of arsenobetaine was confirmed by spiking an extract of the ants with synthetic arsenobetaine bromide.
TL;DR: In this paper, the same type of octahedral structure as was previously found for 2-mercaptopyridine (HSPy) 4 and SnCI 2 (SPym) 2 was inferred for the other solid RSnL 3 compounds, except for RsnCIL 2 and RSnCI 2 L.
Abstract: Mono-organotin(IV) and tin(IV) derivatives of 2-mercaptopyridine (HSPy) and 2-mercaptopyrimidine (HSPym), RSnL 3 (R=Me, n-Bu, Ph; L=SPy, SPym; R=Bz=benzyl, o-CIBz, oClC 6 H 4 , p-ClC 6 H 4 , o-tolyl, p-tolyl; L=SPy), RSnCIL 2 (R=Me, n-Bu, Ph; L=SPy, SPym), RSnCI 2 L (R=Me, n-Bu; L=SPy, SPym) and SnCI 4-n L n (L=SPy, SPym; n=2,4) were obtained from RSnCI 3 or SnCI 4 and NaL or by neutralization (R=Ph,p-tolyl; L=SPy, SPym). RSnCIL 2 and RSnCI 2 L were better prepared by comproportionation of RSnCI 3 and RSnL 3 . MeSn(Spy) 3 and PhSn(SPy) 3 .1.5CHCI 3 crystals, as determined by single-crystal X-ray diffraction, are monoclinic. In the discrete monomeric RSn(SPy) 3 units, three bidentate SPy ligands together with R form a distorted pentagonal bipyramid around tin. One S and the C(R) atom are in the axial positions. Two S atoms and three N atoms form the pentagonal plane. From 119 Sn Mossbauer and IR data, analogous structures are inferred for the other solid RSnL 3 compounds, except for R=Bz, o-CIBz, o-CIC 6 H 4 and o-tolyl, in which tin would be hexacoordinated. In the compounds RSnCIL 2 and RSnCI 2 L, tin is at the center of an octahedron or a trigonal bipyramid, respectively. For Sn(SPym) 4 and SnCI 2 (SPym) 2 , the same type of octahedral structure as was previously found for Sn(Spy) 4 .HSPy and SnCI 2 (Spy) 2 is proposed. According to IR and 1 H, 13 C and 119 Sn NMR data, the solid-state molecular structures are retained in chloroform and dimethyl sulfoxide solution.