ISSN:0268-2605    

DOI:10.1002/aoc.590080402

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA study of Group 14 organometallic compounds using17O NMR spectroscopy carried out at the Latvian Institute of Organic Synthesis has been reviewed. The main areas of17O NMR application—studies of electronic effects, conformational analysis and coordinative interactions—have been characteri

ISSN:0268-2605    

DOI:10.1002/aoc.590080403

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis review describes determinations of mercury compounds under three categories: total mercury; separate determinations of inorganic mercury(II) and organomercury compounds by selective reduction; and speciation of inorganic mercury(II), monomethylmercury cation, and dimethylmercury. Topics described for each category include sample treatment, separation, detection, and limit of detection. Finally, we note that most methods would not detect dimethylmercury if it were present.

ISSN:0268-2605    

DOI:10.1002/aoc.590080404

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe separation and identification of some of the arsenic species produced in cells present in the growth medium when the microorganismsApiotrichum humicola(previously known asCandida humicola) andScopulariopsis brevicauliswere grown in the presence of arsenicals were achieved by using hydride generation–gas chromatography–atomic absorption spectrometry methodology (HG GC AA). Arsenite, monomethylarsonate, dimethylarsinate and trimethylarsine oxide were detected following incubation with arsenate. With arsenite as a substrate, the metabolites were monomethylarsonate, dimethylarsinate and trimethylarsine oxide; monomethylarsonate afforded dimethylarsinate and trimethylarsine oxide, and dimethylarsinate afforded trimethylarsine oxide. Trimethylarsine was not detected when the arsenic concentration was 1

ISSN:0268-2605    

DOI:10.1002/aoc.590080405

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolyphysa peniculuswas grown in artificial seawater in the presence of arsenate, arsenite, monomethylarsonate and dimethylarsinic acid. The separation and identification of some of the arsenic species produced in the cells as well as in the growth medium were achieved by using hydride generation–gas chromatography–atomic absorption spectrometry methodology. Arsenite and dimethylarsinate were detected following incubation with arsenate. When the alga was treated with arsenite, dimethylarsinate was the major metabolite in the cells and in the growth medium; trace amounts of monomethylarsonate were also detected in the cells. With monomethylarsonate as a substrate, the metabolite is dimethylarsinate.Polyphysa peniculusdid not metabolize dimethylarsinic acid when it was used as a substrate. Significant amounts of more complex arsenic species, such as arsenosungars, were not observed in the cells or medium on the evidence of flow injection–microwave digestion–hydride generation–atomic absorption spectrometry methodology. Transfer of the exposed cells to fresh medium caused release of most cell–associated arsenicals to the surrounding

ISSN:0268-2605    

DOI:10.1002/aoc.590080406

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractTolerance, bioaccumulation, biotransformation and excretion of arsenic compounds by the fresh–water shrimp (Neocaridina denticulata) and the killifish (Oryzias latipes) (collected from the natural environment) were investigated. Tolerances (LC50) of the shrimp against disodium arsenate [abbreviated as As(V)], methylarsonic acid (MAA), dimethylarsinic acid (DMAA), and arsenobetaine (AB) were 1.5, 10, 40, and 150μg As ml−1, respectively.N. denticulataaccumulated arsenic from an aqueous phase containing 1 μg As ml−1of As(V), 10 μg As ml−1of MAA, 30 μg As ml−1of DMAA or 150 μg As ml−1of AB, and biotransformed and excreted part of these species. Both methylation and demethylation of the arsenicals were observedin vivo. When livingN. denticulataaccumulating arsenic was transferred into an arsenic–free medium, a part of the accumulated arsenic was excreted. The concentration of methylated arsenicals relative to total arsenic was higher in the excrement than in the organism.Total arsenic accumulation in each species via food in the food chainGreen algae (Chlorella vulgaris)→ shrimp (N. denticulata)→ killifish (O. latipes)decreased by one order of magnitude or more, and the concentration of methylated arsenic relative to total arsenic accumulated increased successively with elevation in the trophic level. Only trace amounts of monomethylarsenic species were detected in the shrimp and fish tested. Dimethylarsenic species in alga and shrimp, and trimethylarsenic species in killifish, were the predominant methylated arsenic

ISSN:0268-2605    

DOI:10.1002/aoc.590080407

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThree polymers containing Bu2SnX (X=OAc or Cl) groups linked to the polymer through a C–Sn bond have been prepared by hydrostannation (via Bu2Sn HCl) of the following CH=CH2h‐containing polymers: (1) a polybutadiene containing approx. 70% of 1,2 CH=CH2units; (2) poly(allyl methacrylate); (3) poly(tetraethylene glycol monoallyl ether methacrylate). The first and third were tested for activity against a number of marine organisms and found to be inactive. Presumably this observed biological inactivity arises from the fact that R3Sn(H2O) n+ions are not released into the aqueous m

ISSN:0268-2605    

DOI:10.1002/aoc.590080408

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMethyltin compounds (MeSn) which do not originate from man–made pollution are common in estuaries and particularly in salt marshes containing the marsh grassSpartina alterniflora. This study reports the results of experiments in which estuarine water containingS. alternifloraleaves is spiked with inorganic tin, and estuarine water alone is spiked with inorganic tin and MeSn. When decaying leaves are present, inorganic tin concentrations in the water decrease and there is a 10‐fold increase in inorganic tin concentration in the leaves. This biosorption follows pseudo–first–order kinetics. MeSn3+and Me2Sn2+occur occasionally in the water. The Me2Sn2+concentration decreases with time and the Me3Sn2+concentration increases with time inS. alternifloraleaves. The results of estuarine water amended with inorganic tin and MeSn in the absence of leaves are quite different. The overall inorganic tin concentration decreases significantly during the experiment, the MeSn3+concentration is approximately constant, and concentrations of Me2Sn2+and Me3Sn+increase. This means that net methylation of inorganic tin has occurred. We conclude that decayingS. alterniflorais likely to be important in the cycling of tin in salt

ISSN:0268-2605    

DOI:10.1002/aoc.590080409

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPalladium colloids revealing narrow particle size distributions can be obtained by chemical reduction using tetra–alkylammonium hydrotriorganoborates. Combining the stabilizing agent [NR 4+] with the reducing agent [BEt3H−] provides a high concentration of the protecting group at the reduction centre. Alternatively, NR4X (X = halogen) may be coupled to the metal salt prior to the reduction step: addition of N(octyl)4Br to Pd(ac)2in THF, for example, evokes an active interaction between the stabilizing agent and the metal salt. Reduction of NR 4+‐stabilized palladium salts with simple reducing agents such as hydrogen at room temperature yields stable palladium organosols which may be isolated in the form of redispersible powders. The anion of the palladium salt is crucial for the success of the colloid synthesis. Electron microscopy shows that the mean particle size ranges between 1.8 and 4.0 nm. An X–ray–photoelectron spectrscopic examination demonstrated the presence of zerovalent palladium.These palladium colloids may serve as both homogeneous and heterogeneous hydrogenation catalysts. Adsorption of the colloids onto industrially important supports can be achieved without agglomeration of palladium particles. The standard activity of a charcoal catalyst containing 5% of colloidal palladium determined through the cinnamic acid standard test was found to exceed considerably the activity of the conventional technical catalysts. In addition, the lifespan of the catalyst containing a palladium colloid, isolated from the reduction of [N(octyl)4]2PdCl2Br2with hydrogen, is superior to conventionally prepared palladium/charcoal (Pd/C) catalysts. For example, the activity of a conventional Pd/C catalyst is completely suppressed after 38×103catalytic cycles per Pd atom, whereas the colloidal Pd/C catalyst shows activity even after 96times;103ca

ISSN:0268-2605    

DOI:10.1002/aoc.590080410

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractLaser photodissociation of trimethylaluminum and trimethylindium at 248 nm on a quartz substrate was studied by detecting aluminum and indium atoms appearing as reaction intermediates by laser–induced fluorescence. Photodissociation occurred predominantly in the adsorbed state in the experimental conditions. Kinetic energy distributions of the atoms were measured and were simulated by Maxwell–Boltzmann distributions in order to discuss photodissociation mechani

ISSN:0268-2605    

DOI:10.1002/aoc.590080411

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY