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Ohne Zusammenfassung 相似文献
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Ohne Zusammenfassung 相似文献
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W. Rathje F. Fichter E. Jenny K. N. Moros 《Analytical and bioanalytical chemistry》1939,117(11-12):420-423
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Rud Wegscheider w. M. K. Akad Ernst Späth 《Monatshefte für Chemie / Chemical Monthly》1916,37(4-5):277-303
Ohne ZusammenfassungHerrn Hofrat V. v. Lang sagen wir für die Ausführung der Krystallmessungen besten Dank. 相似文献
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Edi?Bralatei Karolina?Nekrosiute Jenny?Ronan Andrea?Raab Evin?McGovern Dagmar?B.?Stengel Eva?M.?Krupp Joerg?FeldmannEmail authorView authors OrcID profile 《Mikrochimica acta》2017,184(6):1701-1709
Inorganic arsenic (iAs) in 13 store-bought edible seaweed samples and 34 dried kelp (Laminaria digitata) samples was determined by a newly developed, field-deployable method (FDM) with the aid of a field test kit for arsenic in water. Results from the FDM were compared to results from speciation analysis achieved by using high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The FDM consisted of a simple extraction method using diluted HNO3 to quantitatively extract iAs without decomposing the organoarsenicals to iAs followed by the selective volatilisation of iAs as arsine (AsH3) and subsequent chemo-trapping on a filter paper soaked in mercury bromide (HgBr2) solution. Method optimization with a sub-set of samples showed 80–94% iAs recovery with the FDM with no matrix effect from organo-arsenic species in the form of dimethylarsinic acid (DMA) on the iAs concentration. The method displayed good reproducibility with an average error of ±19% and validation by HPLC-ICP-MS showed that the results from the FDM were comparable (slope = 1.03, R2 = 0.70) to those from speciation analysis with no bias. The FDM can be conducted within an hour and the observed limit of quantification was around 0.05 mg kg?1 (dry weight). This method is well suited for on-site monitoring of iAs in seaweed before it is harvested and can thus be recommended for use as a screening method for iAs in seaweed. 相似文献
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The anharmonic OH stretching vibrational frequencies, ν(OH), for the first-shell water molecules around the Li(+), Ca(2+), Mg(2+), and Al(3+) ions in dilute aqueous solutions have been calculated based on classical molecular dynamics (MD) simulations and quantum-mechanical (QM) calculations. For Li(+)(aq), Ca(2+)(aq), Mg(2+)(aq), and Al(3+)(aq), our calculated IR frequency shifts, Δν(OH), with respect to the gas-phase water frequency, are about -300, -350, -450, and -750?cm(-1), compared to -290, -290, -420, and -830?cm(-1) from experimental infrared (IR) studies. The agreement is thus quite good, except for the order between Li(+) and Ca(2+). Given that the polarizing field from the Ca(2+) ion ought to be larger than that from Li(+)(aq), our calculated result seems reasonable. Also the absolute OH frequencies agree well with experiment. The method we used is a sequential four-step procedure: QM(electronic) to make a force field+MD simulation+QM(electronic) for point-charge-embedded M(n+) (H(2)O)(y) (second?shell) (H(2)O)(z) (third?shell) clusters+QM(vibrational) to yield the OH spectrum. The many-body Ca(2+)-water force-field presented in this paper is new. IR intensity-weighting of the density-of-states frequency distributions was carried out by means of the squared dipole moment derivatives. 相似文献
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Novel flame retardants containing cyclodextrin nanosponges and phosphorus compounds to enhance EVA combustion properties 总被引:1,自引:0,他引:1
Jenny Alongi Merima Poškovi? Francesco Trotta 《Polymer Degradation and Stability》2010,95(10):2093-2100
A novel flame retardant intumescent system, aimed to improve the fire stability of ethylene vinyl acetate copolymer (EVA), has been prepared by melt blending of the copolymer and a complex of cyclodextrin nanosponge-phosphorus compounds. As compared to traditional systems, this complex, stable in processing conditions, has the advantage that nanosponges act as both carbon sources and foam forming agents while the phosphorus compounds are able to directly generate phosphoric acid in situ. In this context, cyclodextrin nanosponges undergo dehydration in presence of the acid source, generating water vapour and char, and thus protecting the copolymer against combustion. Different acid sources have been investigated in order to reach the optimum interaction with the nanosponges. Raman measurements and thermogravimetric analyses have shown that the cavities of nanosponges entrapped the phosphorus derivatives forming stable complexes at the temperature of EVA processing. Different amounts of these complexes (5, 10 and 15 wt.%) have been added to EVA via melt blending and their flame retardancy properties measured by UL94 test and cone calorimetry. Strongly modified burning kinetics, as compared to the behaviour of the neat copolymer, have been found by UL94 test: V2 classification has been achieved for every formulation regardless of the type and the amount of complex used. EVA combustion behaviour by cone calorimetry has also been significantly affected: the heat release rate decreased dramatically down to ca. 20% in the presence of these new additives. 相似文献
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