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31.
The performance of calcium ion-selective microelectrodes based on a neutral carrier for extra- and intra-cellular measurements of free Ca2+ ions as reported in the recent literature is assessed. A novel membrane consisting of readily available components is presented which overcomes the technical problems associated with very fine electrode tips. Measured selectivity factors, log KpotCaM, for M2+ = Na+, K+, and Mg2+ are -5.5, -5.4, and <-4.9, respectively. 相似文献
32.
Speciation of heavy metals in environmental water by ion chromatography coupled to ICP–MS 总被引:3,自引:0,他引:3
Ammann AA 《Analytical and bioanalytical chemistry》2002,372(3):448-452
Biogenic (e.g. phytochelatins, porphyrins, DOM) as well as anthropogenic (e.g. NTA, EDTA, phosphonates) chelators affect the mobility and cycling of heavy metals in environmental waters. Since such chelators can form strongly bound anionic heavy metal complexes that are stable and highly mobile, anion-exchange chromatography coupled to ICP-MS was investigated. A narrow bore HPLC system was connected to a micro concentric nebuliser for in-line sample introduction. A new chromatographic procedure based on a synthetic hydrophilic quaternary ammonium anion exchanger in combination with nitrate as a strong eluent anion, and gradient elution, provided high separation selectivity and a large analytical window. Low detection limits (nmol L(-1)) were achieved by on-column matrix removal and sample preconcentration. This allowed the method to be successfully applied to different environmental research areas. In ecotoxicological studies of heavy metal effects on algae low concentrations of metal EDTA complexes were determined in nutrient solutions without interference from high (buffer) salt concentrations. In groundwater, infiltrated by a polluted river, mobile metal EDTA species were observed. In river water of different pollution levels beside CuEDTA other anionic Cu-complexes were found in nmol L(-1) concentrations. 相似文献
33.
Frank Bongardt Fritz Vgtle Dorothe Wegmann Daniel Ammann Takuya Maruizumi Wilhelm Simon 《Helvetica chimica acta》1987,70(1):153-157
Preparation of Neutral Sodium-Selective Ionophores and their Characterization in Membrane Electrodes Different ionopbores based on N,N′-dibenzyl-N,N′-diphenyl-1,2-phenylenedioxydiacetamide ( 1 ) have been prepared by substitution of the aromatic ring carrying the ether O-atoms. Substituents of widely different electronegativity (CH3, CH3O, CHO, CN NO2, Br) do not relevantly influence the ion selectivity. 相似文献
34.
Lipophilic Synthetic Monoamides of Dicarboxylic Acids as Ionophores for Alkaline Earth Metal Cations
Magdalena Maj-Zurawska Daniel Erne Daniel Ammann Wilhelm Simon 《Helvetica chimica acta》1982,65(1):55-62
N, N-Dioctadecyl-substituted lipophilic monoamides of certain dicarboxylic acids have been prepared. It is shown that they induce a transport of alkaline earth metal cations through solvent polymeric membranes coupled to a counter transport of hydrogen ions or K+. They proved to be suitable components for ion-selective electrodes. 相似文献
35.
In connection with studies on heterodiamantanes and structurally related compounds the two novel pentacyclic diethers 9 and 10 were prepared starting from the photo-dimer 8 of cyclopentadienone. All three compounds have as common features a central carbocyclic 6membered ring with four axial alkyl substituents and two oxygen function in 1,4-position. The diether 9 was obtained on the one hand from the intermediate tetracyclic unsaturated alcohol 23 by intramolecular addition, catalyzed either by acid or base (scheme 3), and on the other hand from the tetracyclic diol 32 or the dibromoketones 34 (via 38 ) and 35 (via 39 ) by intramolecular substitution (schemes 4 and 5). The synthesis of the isomeric diether 10 was achieved by intramolecular substitution of the tetracyclic diol 33 (scheme 4). Diether 9 is thermodynamically more stable than 10 . The latter was easily isomerized to the former on treatment with concentrated sulfuric acid in benzene. 相似文献
36.
Jean-Claude C. Bünzil Jean-Marc Pfefferl Bruno Ammann Gervais Chapuis F.-Javier Zuniga 《Helvetica chimica acta》1984,67(4):1121-1127
The crystal and molecular structure of [La(NO3)3]4(C12H26O5)3 has been determined from low-temperature single-crystal X-ray diffraction data. The complex crystallizes in the monoclinic space group I2 with Z = 2. Lattice parameters at 150 K are a = 12.234 (6) Å, b = 11.105 (5), c = 26.613 (9), β = 90.65 (4)°. The structure was solved by Patterson and Fourier techniques and refined to a conventional RF-value of 0.068. The compound contains three dinitrato complex cations [La(NO3)2C12H26O6]+ with 10-coordinate lanthanum ions and one hexanitrato anion, [La(NO3)6]3?, with a 12-coordinate La(III)-ion. One complex cation has a C2-symmetry while the two others, which are crystallographically equivalent, have no symmetry and contain a disordered ligand molecule. The polyther adopts a ring-like conformation in all the complex moietis. The La? O(nitrate) distances lie in the ranges 2.52–2.53 and 2.49–2.62 Å, with average values of 2.53 (7) and 2.56 (6) Å, respectively, fo the species with C2- and C1-symmetry; the La? O(ether) bond lengths lie int he range 2.54–2.79 Å (average: 2.6 (1)) for the C2-moiety and their mean value amounts to 2.6 (2) for the disordered species. The hexanitrate has a C2-symmetry and the La? O distances range between 2.56 and 2.67 Å with an average value fo 2.64 (4) Å. The effective ionic radii of the 10- and 12-coordinate La(III) ions are estimated as 1.28 and 1.33 Å, respectively. 相似文献
37.
38.
Andreas Ammann Dirk C. Hinz R. Shane Addleman Chien M. Wai B. W. Wenclawiak 《Fresenius' Journal of Analytical Chemistry》1999,364(7):650-653
Superheated water extraction, steam distillation and supercritical fluid extraction (SFE) are compared for extraction of
l-menthol, menthone, eucalyptol and other components of peppermint (mentha piperita) leaves. Different temperatures and pressures were investigated. SFE results at 25/40 °C and 6.5/8/10 MPa were comparable
with those reported in the literature. Although SFE is a gentle way of extracting thermally unstable compounds, this method
is too slow for commercial use in comparison with steam distillation at 100 °C. Superheated water extraction at 125/150 °C
and 1–2 MPa exhibits higher extraction efficiency than the SFE method. Comparison of all experiments under the chosen conditions
shows steam distillation to be the most effective extraction method.
Received: 18 January 1998 / Revised: 9 April 1999 / Accepted: 15 April 1999 相似文献
39.
Selective ionophores of extreme lipophilicity for liquid membrane electrodes Lipophilic ionophores of the type diether diamides have been prepared. Their lipophilicity is up to 7 orders of magnitude higher than the one of the most lipophilic ion carriers used as selective components in liquid membrane electrodes reported so far. For such ion carriers of extremely high lipophilicity kinetic limitations of the carrier induced ion transfer between aqueous and membrane phase usually dominate and heavily disturb the electromotive behavior of the membrane electrode. These limitations are absent only in those cases where most of the lipophilic segments of the carrier may remain in the membrane phase while the segments with the coordination sites are exposed to the aqueous phase during the transfer process. 相似文献
40.
René Stepánek Bernhard Kräutler Peter Schulthess Bernhard Lindemann Daniel Ammann Wilhelm Simon 《Analytica chimica acta》1986
The synthesis of aquocyanocobalt(III)-hepta(2-phenylethyl)-cobyrinate is described. It is a more lipophilic substitute for a previously reported nitrite-carrier. Membranes based on this more readily accessible cobyrinate exhibit selectivity coefficients for nitrite (Kpot) over nitrate and chloride of 10?4.2 and 10–4.6, respectively. Near-theoretical slopes were found for 10?4.5?10?1.0 M nitrite. After contact of the sensor with flowing tap water for 35 days, no deterioration of the electrode characteristics was observed. 相似文献