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11.
Zusammenfassung Wäßrige und organische Lösungen (Äther, Benzol, Chloroform, Pentan) von Milchsäure wurden gas-chromatographisch untersucht. Dabei wurden neben dem Peak der monomeren Verbindung noch 4 weitere Peaks von Kondensationsprodukten gefunden. Der Anteil der einzelnen Komponenten am Gesamtgehalt war je nach Konzentration der untersuchten Lösung und Art des Lösungsmittels verschieden (Tabelle).
Gas-chromatographic analysis of solutions of dl-lactic acid
Aqueous and organic solutions (ether, benzene, chloroform, pentane) of lactic acid have been submitted to gas chromatography. Besides of the peak of the monomeric compound four other peaks have been detected corresponding to condensation products. The percentage of the different components depended on the concentration of the solutions and the kind of solvent.相似文献
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The performance of graphitized glass capillary columns obtained by precoating the inner glass walls with graphitized carbon black has been evaluated. It has been shown that according to the amount of stationary phase coated such columns can operate in gas–liquid-solid chromatography and in gas–liquid chromatography so that tailor-made columns for specific separations can be prepared. The versatility of these columns is shown in the separation of various mixtures (terpenes, pesticides, isomeric species and others) of analytical importance. 相似文献
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Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples is carried out after adsorption
from a 25–500 mL sample, on a cartridge containing 100 mg aminopropyl-bonded porous silica. The clean-up step in which the
PCBs and chlorinated pesticides are separated in different eluates is achieved by passing 25 mL of 40% aqueous methanol through
the NH2 Sep-Pak cartridge. The PCBs are desorbed with 500 μL ethylacetate, which is concentrated and analysis by GC-ECD. The average
recovery, at 1 ppb is >97% with a standard deviation <2. The limits of detection are 0.1 ng μL−1 and 5 pg μL−1 respectively for Cl3-PCB and Cl8-PCB congeners. In the separation of PCBs from the chlorinated pesticides tested in this work, only the Aldrin is adsorbed
for 60% with the PCBs by the NH2 Sep-Pak cartridge. The method described is rapid, simple and reproducible. 相似文献
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Exceptionally Inert Lanthanide(III) PARACEST MRI Contrast Agents Based on an 18‐Membered Macrocyclic Platform
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Goretti Castro Dr. Martín Regueiro‐Figueroa Dr. David Esteban‐Gómez Dr. Rufina Bastida Dr. Alejandro Macías Dr. Paulo Pérez‐Lourido Dr. Carlos Platas‐Iglesias Dr. Laura Valencia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18662-18670
We report a macrocyclic ligand based on a 3,6,10,13‐tetraaza‐1,8(2,6)‐dipyridinacyclotetradecaphane platform containing four hydroxyethyl pendant arms (L1) that forms extraordinary inert complexes with Ln3+ ions. The [EuL1]3+ complex does not undergo dissociation in 1 M HCl over a period of months at room temperature. Furthermore, high concentrations of phosphate and Zn2+ ions at room temperature do not provoke metal‐complex dissociation. The X‐ray crystal structures of six Ln3+ complexes reveal ten coordination of the ligand to the metal ions through the six nitrogen atoms of the macrocycle and the four oxygen atoms of the hydroxyethyl pendant arms. The analysis of the Yb3+‐ and Pr3+‐induced paramagnetic 1H NMR shifts show that the solid‐state structures are retained in aqueous solution. The intensity of the 1H NMR signal of bulk water can be modulated by saturation of the signals of the hydroxy protons of Pr3+, Eu3+, and Yb3+ complexes following chemical‐exchange saturation transfer (CEST). The ability of these complexes to provide large CEST effects at 25 and 37 °C and pH 7.4 was confirmed by using CEST magnetic resonance imaging experiments. 相似文献
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Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples has been performed after adsorption
from a 50–250 mL sample on to a cartridge containing 100 mg cyanopropyl-bonded porous silica. The PCBs are desorbed with 500
μL ethyl acetate, which is concentrated and analysed by gas chromatography with electron-capture detection (GC-ECD).
The average recovery of 1 ppb PCB congeners at from distilled water and from Marta river water is ≥95% (standard deviation
≤2.5). The average recovery of 20 ppb Aroclor 1260 from Marta river water was ≥91% (standard deviation ≤3.5).
In the separation of the PCBs from the chlorinated pesticides only aldrin, heptachlor and 4,4′-DDD are adsorbed with the PCBs
by the CN Sep-Pak cartridge. The method proposed is rapid, simple and reproducible. 相似文献
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Bellini G Benziger J Bick D Bonetti S Bonfini G Bravo D Buizza Avanzini M Caccianiga B Cadonati L Calaprice F Carraro C Cavalcante P Chavarria A Chepurnov A D'Angelo D Davini S Derbin A Etenko A Fomenko K Franco D Galbiati C Gazzana S Ghiano C Giammarchi M Goeger-Neff M Goretti A Grandi L Guardincerri E Hardy S Ianni A Ianni A Korablev D Korga G Koshio Y Kryn D Laubenstein M Lewke T Litvinovich E Loer B Lombardi F Lombardi P Ludhova L Machulin I Manecki S Maneschg W Manuzio G Meindl Q Meroni E 《Physical review letters》2012,108(5):051302
We observed, for the first time, solar neutrinos in the 1.0-1.5 MeV energy range. We determined the rate of pep solar neutrino interactions in Borexino to be 3.1±0.6{stat}±0.3{syst} counts/(day·100 ton). Assuming the pep neutrino flux predicted by the standard solar model, we obtained a constraint on the CNO solar neutrino interaction rate of <7.9 counts/(day·100 ton) (95% C.L.). The absence of the solar neutrino signal is disfavored at 99.97% C.L., while the absence of the pep signal is disfavored at 98% C.L. The necessary sensitivity was achieved by adopting data analysis techniques for the rejection of cosmogenic {11}C, the dominant background in the 1-2 MeV region. Assuming the Mikheyev-Smirnov-Wolfenstein large mixing angle solution to solar neutrino oscillations, these values correspond to solar neutrino fluxes of (1.6±0.3)×10{8} cm{-2}?s^{-1} and <7.7×10{8} cm{-2}?s{-1} (95% C.L.), respectively, in agreement with both the high and low metallicity standard solar models. These results represent the first direct evidence of the pep neutrino signal and the strongest constraint of the CNO solar neutrino flux to date. 相似文献
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Summary Glass microbead columns withN, N-bis-(p-butoxybenzilidene) , -bi-p-toluidine (BBBT) a high-temperature smectic-nematic liquid crystalline stationary phase have been prepared. The best efficiency was obtained with BBBT from 0.025% w/w (ca. 1800 theoretical plates m–1) to 0.1% w/w (ca. 2100 theoretical plates m–1). Capacity ratios and separation efficiencies of columns packed with glass microbeads treated and untreated with a surfaceactive agent were studied as a function of analysis time. A separation of five methylchrysene isomers is shown. 相似文献